Accurate prediction of tropical cyclone (TC) intensity still faces great challenges, and rapid intensification (RI) imposes the largest uncertainty in forecasting the TC intensity change. TC RI has been extensively studied, but most studies considered RI during an 24h period, but not the whole life cycle of the RI event. This study investigates the characteristics and environmental factors of ~1500 full lifecycle RI events from 1980 to 2020 in global TCs and compare their regional difference. Our results show that most RI events actually initiate at the tropical storm stage (30-40 kts) preferentially in the early morning, which is consistent across basins. The locations of RI onsets in the southern hemisphere are generally limited between 9°S and 20°S, while in the northern hemisphere, they occur at higher latitudes, particularly in the North Atlantic, reaching above 30°N. Nearly half of the RIs last longer than 42h, and RIs in the western North Pacific last significantly longer than RIs in the North Atlantic and South Indian. It is interesting that no matter the initial intensity, RI events with longer duration have higher intensification rate (INTRATE), except for extremely lasted events. Also, the total intensification amplitudes of RIs are more determined by the duration than the INTRATE. Overall, the duration and INTRATE of RIs have a positive relationship with maximum potential intensity (MPI), SST and mid-level relative humidity, and a negative relationship with vertical wind shear. Of course, the initial environmental conditions for RIs are more favorable than regularly intensifying events. It is intriguing whether environments of extreme RIs (extremely high INTRATE) differ from normal RIs, which will be further investigated.
How to cite: Li, M., Xu, W., and Zhang, X.: Global and Regional Characteristics of Tropical Cyclone Rapidly Intensifying Events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9467, https://doi.org/10.5194/egusphere-egu25-9467, 2025.
This study investigates the rain microphysics of tropical cyclones (TCs) that underwent rapid (RI) and slow intensification (SI). TCs that formed in the North Indian Ocean (NIO) are considered, particularly over the Arabian Sea (AS) and Bay of Bengal (BOB) regions for years 2014-2023. Among the 114 TCs recorded in NIO, 42 underwent intensification (RI-22; SI-20). The probability density functions (PDFs) of rain microphysics parameters vary with the intensification mode (RI and SI) and the type of rain (total, stratiform, and convective). The storm height is slightly taller in RI than SI TCs, most notably in convective systems, which underscores the structural difference between the two intensification categories. The contour frequency by altitude diagrams, as well as the vertical mean profiles, reveal that for all rain types, RI TCs have higher rain rates (R), stronger reflectivity (𝑍), larger drop size diameters (𝐷𝑚), and lower drop concentrations (𝑁𝑤) as compared to SI TCs. Results from this study may be used to delineate an impending RI from SI.
How to cite: Jalakam, S. P., Lin, P.-L., Chang, W.-Y., Seela, B. K., and Janapati, J.: Rain Microphysical Characteristics of Rapidly and Slowly Intensifying Tropical Cyclones over North Indian Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-657, https://doi.org/10.5194/egusphere-egu25-657, 2025.
Hurricane rapid intensification (HRI) refers to a phenomenon in which a tropical cyclone undergoes a sudden and significant increase in wind speed over a short period, typically defined as an increase of at least 35 mph (30 knots) in maximum sustained winds within 24 hours. Key factors influencing the rapid intensification phenomenon are the presence of warm sea surface temperatures (SSTs) in combination with significant ocean heat content, a low wind shear, a high atmospheric water vapour content, as well a pre-existing well-organized storm structure. The combination of these factors can lead to disruptive HRI as observed for Hurricane Milton (2024), whose winds increased by 78 knots in the 24-hour period from 00:00 UTC October 7 to 00:00 UTC October 8. Monitoring and predicting HRI is crucial for disaster preparedness: a WRF hindcast study at 1.5 km grid spacing for Milton, which well reproduce the trajectory of the hurricane and its maximum wind intensity is presented.
The simulated Hurricane Milton three dimensional cloud and wind structure has been exploited to assess how the WIVERN 94 GHz radar, currently under study in the ESA Earth Explorer program, could sample the systems in correspondence to successive orbits during the hurricane lifetime. The proposed WIVERN radar has ground-breaking Doppler and scanning capabilities that enable to map very strong winds across a large swath of the order of 800 km (Illingworth et al., 2018; Battaglia et al.,2022, Tridon et al., 2023). Different overpasses simulated before and after the HRI demonstrate that the WIVERN system will be able to provide, for the first time from space, information about the mesoscale vertical structure of clouds and dynamics of the cyclone, particularly in the region above the freezing level (94 GHz are strongly attenuated inside the convective regions and the heavily precipitating rain bands). This suggests that WIVERN observations may have great potential to improve the prediction of hurricane intensification.
Illingworth, A. J., Battaglia, A. et al., 2018: Wivern: A new satellite concept to provide global in-cloud winds, precipitation and cloud properties. Bull.Amer. Met. Soc., DOI: 10.1175/BAMS-D-16-0047.1, 1669-1687.
Battaglia, A., Martire, P., Caubet, E., Phalippou, L., Stesina, F., Kollias, P., and Illingworth, A.: Observation error analysis for the WInd VElocity Radar Nephoscope W-band Doppler conically scanning spaceborne radar via end-to-end simulations, Atmos. Meas. Tech., 15, 3011–3030, https://doi.org/10.5194/amt-15-3011-2022, 2022.
Tridon, F., Battaglia, A., Rizik, A., Scarsi, F. E., & Illingworth, A., 2023: Filling the gap of wind observations inside tropical cyclones. Earth and Space Science, 10, e2023EA003099. https://doi.org/10.1029/2023EA003099
How to cite: Battaglia, A., Milelli, M., Lagasio, M., Rabino, R., Tridon, F., Pourshamsi, M., Kleinherenbrink, M., and Parodi, A.: Advancing spaceborne observations of tropical cyclones by the WIVERN 94 GHz Doppler radar: the case study of the rapid intensification of hurricane Milton, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14926, https://doi.org/10.5194/egusphere-egu25-14926, 2025.
The classic theories on tropical cyclone (TC) intensification (i.e., CISK, WISHE) are based on the assumption of an axisymmetric and vertically aligned TC circulation. However, how the TC vortices align at various altitudes within a sheared environment is a challenging topic in the TC intensity change research. This study investigates vortex alignment in tropical cyclones (TCs) through two idealized experiments conducted under easterly vertical wind shears (VWS) of 6 m s⁻¹ and 10 m s⁻¹. Both experiments simulate TCs that exhibit intensification simultaneously. While the onset of intensification hinges on the achievement of a vertically aligned vortex structure, the evolution of vortex tilt displays significant differences between the two cases. We find the crucial role of convective asymmetry, predominantly intensified on the downtilt side of the simulated TCs, in driving vortex alignment.On one hand, diabatic heating associated with the asymmetric convection directly aids in reducing the vortex tilt. On the other hand, this convective asymmetry generates counter-rotating gyres within the inner-core region. These gyres produce cyclonic vorticity downstream of the heating zone and anticyclonic vorticity downstream of the cooling zone, which obstructs vertical structure coupling. The interplay between these processes ultimately dictates the evolution of vortex tilt. This research emphasizes the importance of capturing convective processes to improve the TC intensification prediction.
How to cite: Feng, Y. and Wu, L.: Influences of Asymmetric Convection on Vortex Alignment of Tropical Cyclones: Idealized Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3660, https://doi.org/10.5194/egusphere-egu25-3660, 2025.
The intensification of tropical cyclones (TCs) results from the transport of conserved angular momentum, at least in an axisymmetric context. While there is general agreement on the role of moist cloud convection in driving the system, its precise contribution to intensification remains unclear. Additionally, the mechanisms by which convection facilitates angular momentum transport are still not well understood.
Two prominent but seemingly contradictory explanations for this phenomenon exist in the literature: the Conditional Instability of the Second Kind (CISK) and Wind-Induced Surface Heat Exchange (WISHE). Although these models offer different perspectives, we propose that they represent limiting, asymptotic scaling regimes of the same underlying physical process.
To reconcile these differing views, we use matched asymptotics to combine the three distinct regimes suggested by CISK and WISHE, thus providing a unified framework. Our analysis shows that the transport of angular momentum plays a crucial role in ensuring consistency with the asymptotic matching principle.
Interestingly, this work uncovers a new, previously undocumented pathway for angular momentum transport that may serve as a plausible mechanism for TC intensification. A key element of this process is the special role of the top-of-boundary-layer (BL) inflow, which is closely linked to the entrainment of convective cloud towers.
Through this combined approach, we offer a fresh perspective on TC intensification dynamics, confirming the validity of CISK and WISHE within their respective scopes and reconciling them into a more general theory.
How to cite: Dörffel, T., Klein, R., Doppler, S., and Khouider, B.: The role of entrainment in axisymmetric tropical cyclones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18675, https://doi.org/10.5194/egusphere-egu25-18675, 2025.
Classical models of tropical cyclone intensification often predict that cyclones will intensify to a steady-state intensity determined primarily by surface fluxes, while convection maintains the atmosphere close to a neutrally stable state (Emanuel et al. (2003); Emanuel (1995)). However, simulations using the non-hydrostatic, high-resolution SAM model under idealized conditions (rotating radiative-convective equilibrium in a doubly-periodic domain) reveal a more complex intensity evolution.
While the early intensification aligns with theoretical predictions, later in its evolution, the cyclone exhibits oscillations in wind speed. This oscillation can be linked to feedbacks between the cyclone intensity and air buoyancy: convective heating and mixing with warm low stratospheric air warm the mid and upper troposphere of the cyclone, stabilizing the air column and thus reducing its intensity. After the intensity decay phase, mid and upper tropospheric cooling, due to both local longwave radiation emission and cold advection from the surroundings, rebuilds CAPE, that peaks just before a new intensification phase. These idealized simulations highlight the potentially important interactions between a tropical cyclone, its environment and radiation.
References
Kerry Emanuel et al. Tropical cyclones. Annual review of earth and planetary sciences, 31(1):
75–104, 2003.
Kerry A. Emanuel. The behavior of a simple hurricane model using a convective
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How to cite: Polesello, A., Charinti, G. A., Meroni, A. N., Muller, C., and Pasquero, C.: Intensity oscillations of tropical cyclones: surface versus mid and upper tropospheric processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9790, https://doi.org/10.5194/egusphere-egu25-9790, 2025.
It is important to understand how tropical cyclones (TCs) decay over the ocean as this is a critical pre-landfall stage. A modified exponential decay model ($\beta$ model) with two parameters $\alpha$ and $\beta$ is proposed. The scale parameter $\alpha$ defines the decay scale, while the shape parameter $\beta$ determines whether the decay rate decelerates or accelerates over time. Global fittings indicate that around 40\% of TCs exhibit decelerating decay ($\beta \leq 1$), while the majority (about 60\%) show accelerating decay ($\beta > 1$). Correlation analysis reveals a strong negative correlation between the scale parameter $\alpha$ and the initial Coriolis parameter ($r=-0.96$) and a positive correlation between the shape parameter $\beta$ and the meridional component of the initial translation velocity ($r=0.75$). The $\beta$ model provides a comprehensive understanding of how TCs decay with time and how environmental conditions affect the decay scale and evolution.
How to cite: Li, M. and Toumi, R.: On the temporal decay of tropical cyclones over the ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6210, https://doi.org/10.5194/egusphere-egu25-6210, 2025.
Tropical Cyclones (TCs) are devastating natural disasters. Ocean thermal stratification and TC attributes (e.g., translation speed and intensity) have been demonstrated to affect TC intensification via modulating sea surface temperature (SST) cooling effect. Here, we found that both ocean internal tides and storm size could affect TC intensification. Analyzing decades of global TC data, here we explore the modulating role of ocean internal tides and storm size on TC-induced sea surface temperature anomalies (SSTA) and TC intensification in global TC-active oceans. Originating from complex interplays between astronomic tides and the SCS topography, gigantic ocean internal tides in the South China Sea (SCS) interact with TC-generated oceanic near-inertial waves and induce a strong ocean cooling effect, effectively suppressing the TC intensification. Consequently, among all global TC-active basins, the SCS stands out as a particularly difficult ocean for TCs to intensify, despite favorable atmosphere and ocean conditions. Over the SCS, TC intensification rate and its probability for a rapid intensification are only 1/2 and 1/3, respectively, of those for the rest of the world ocean. Moreover, as a typical TC attribute, storm size can also modulate TC intensification through ocean cooling effect. Large TCs induce stronger and more widespread SSTA, which reduces ocean’s enthalpy flux supply and thus suppresses TC intensification globally, as compared to small TCs. This modulating effect emerges in each basin, suggesting a globally consistent effect of storm size on TC intensification through an oceanic pathway. Small TCs, occupying weaker SST cooling and larger enthalpy flux, are more likely to undergo rapid intensification, with the probability of 1.1–1.8 times larger than large TCs in global TC-active oceans. Inclusion of this interaction between internal tides and storm size and TC in operational weather prediction systems is expected to improve forecast of TC intensity in TC-active basins.
How to cite: Guan, S. and Tian, J.: TC-Ocean interaction: modulating roles of ocean internal tides and storm size, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9891, https://doi.org/10.5194/egusphere-egu25-9891, 2025.
Estimating the typhoon sizes, including the radius of maximum wind (RMW) and the wind radii, is a challenging aspect of typhoon monitoring and forecasting. Currently, methods for estimating typhoon sizes include ground-based pressure and wind measurements, airborne Stepped Frequency Microwave Radiometer (SFMR) measurements, satellite-based infrared (IR) and microwave instrument retrievals, etc. Retrievals of sea surface winds based on the microwave scatterometers/radiometers suffer from coarse spatial resolution (40-50 km) and susceptibility to heavy rainfall; meanwhile, IR brightness temperatures lack a direct physical correlation with sea surface winds at the pixel level.
Due to the lack of regular aircraft reconnaissance, the determination of typhoon sizes in the western North Pacific relies solely on IR and microwave retrievals. Our assessment based on synthetic aperture radar (SAR) wind products indicates that the Joint Typhoon Warning Center's (JTWC) best track dataset has a better estimation of typhoon intensities than inner sizes, with an uncertainty within 15% for maximum sustained wind (Vmax) estimation, but as high as 30-60% for RMW estimation, which is above the global average of 25-40%.
This study establishes an RMW estimation algorithm for eyed typhoons based on geostationary satellite IR observations, with key steps including: (a) determining the typhoon center; (b) distinguishing clear-eye cases from unclear-eye cases; (c) estimating the eyewall radius (Reye) separately for clear- and unclear-eye cases; (d) estimating the RMW.
A TC-red-green-blue (TC-RGB) composite was designed by using satellite multichannel observations (reflectance, brightness temperature, and brightness temperature differences), which can effectively differentiate convective clouds, cirrus clouds, and low clouds, proving very effective in identifying exposed low-level circulation centers. Combining the TC-RGB composite image with 10-min atmospheric motion vectors products, a precise typhoon center location can be obtained through interactive human-computer methods. Using SAR positioning results as a reference, the root mean square difference (RMSD) for eyed typhoon positioning results was calculated, with the JTWC dataset direct interpolation result being ~8.6 km, and the interactive method being ~6.6 km, reducing by over 20%.
Subsequently, an objective method to differentiate between clear- and unclear-eye typhoons was established, along with an IR-based method for measuring Reye. For clear-eye typhoons, the calculated Reye has a correlation coefficient as high as 0.89 with the SAR observed RMW (RMW_SAR); for unclear-eye typhoons, the correlation coefficient between Reye and RMW_SAR also reaches 0.82.
Ultimately, an RMW regression equation for eyewall typhoons was established based on Reye and RMW_SAR, with a mean absolute error (MAE) of 5.46 km and a root mean square error (RMSE) of 7.35 km, nearly 40% less than the JTWC dataset.
How to cite: Zhuge, X.: Geostationary Satellite-based Estimation Method for Typhoon Radius of Maximum Wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3650, https://doi.org/10.5194/egusphere-egu25-3650, 2025.
A detailed analysis of temperature and relative humidity biases in the ERA5 reanalysis under tropical cyclone (TC) conditions is conducted using a composite analysis approach. This study incorporates the influences of TC movement and vertical wind shear (VWS). The results show that the temperature bias in the ERA5 data is more pronounced in the core region of TCs than in the outer regions. A similar pattern is observed for relative humidity, but it is most evident in the middle and upper troposphere. Additionally, the temperature bias exhibits a strong asymmetry, particularly in the core region of the TC, where larger errors are observed on the right-front side in the direction of motion and on the front side of the VWS at higher altitudes. This asymmetry is likely associated with more intense convection in these two directions.
How to cite: Chen, Y., Zhao, X., Wei, C., Wang, Y., and Yang, P.: Asymmetry Analysis of ERA5 Reanalysis Data in the Context of Tropical Cyclones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1453, https://doi.org/10.5194/egusphere-egu25-1453, 2025.
Tropical cyclones are one of the most frequent and costly disasters affecting the Small Island Developing States (SIDS) in the Caribbean.
Historical analysis of tropical cyclones in the Caribbean Region (10-30°N 55-90°W), using HURDAT data, shows that the mean Maximum Sustained Wind (MSW) has increased significantly by 30kts since 1965, a rate of 5.3kts per decade with a corresponding significant decrease in the minimum pressure of 2.3mb per decade. The increasing MSW observed is significantly correlated with the August, September and October (ASO) ocean temperatures, which are rising at 0.2ºC per decade in the Caribbean.
TOPIM - Tropical cyclone Ocean-coupled Potential Intensity Model has been developed to better predict tropical cyclone intensity in the Caribbean. TOPIM is an ocean-coupled dynamical and statistical model which has been developed for the Caribbean and already has proof of concept, having been working experimentally for Bermuda since 2021. TOPIMuses subsurface ocean temperature from Argo floats and atmospheric sounding data to improve the prediction of tropical cyclone intensity (wind strength and minimum pressure) in near real-time, using little computing requirements. The model calculates the expected TC potential intensity based on; the average temperature over the top 100m ocean layer in the Caribbean, the local atmospheric sounding data, and local wind pressure relationship for past hurricanes in the area since 1965. The top 100m layer is chosen as it provides the closest prediction of hurricane intensity in the Caribbean region on a hindcast basis since 1990. Results show the prediction better forecasts actual tropical cyclone potential intensity than models using sea surface temperature alone.
TOPIM can also be used for future scenario planning. Past storms can be placed in a warmer ocean environment, to understand the expected increase in maximum sustained wind - an ocean sensitivity analysis. The analysis assumes the atmospheric sounding conditions remain the same. Analysis of historical Caribbean storms suggests a 27kt increase in intensity on average for a 1°C rise in ocean temperature over the top 100m layer.
(Hallam et al. Modelling hurricane Intensity in the Caribbean Region, in prep.)
https://www.topim.org
How to cite: Hallam, S., Hallam, J., Guishard, M., Aird, R., and Campbell, D.: TOPIM – Modelling hurricane Intensity in the Caribbean Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6831, https://doi.org/10.5194/egusphere-egu25-6831, 2025.
Earth system models require high resolution to capture the mesoscale dynamics in the eye of a tropical cyclone (TC), which in turn allows more accurate simulation of TC intensity. We approach this so-called TC-resolving regime by using the coupled ICON model with a 10 km grid spacing in the atmosphere and ocean. Our simulations are 30 years long, which allows us to compute climate statistics for TC frequency and intensity. Although relatively high resolutions have been used before, we are among the first to study tropical cyclones with coupled simulations that have global and multi-decadal coverage at 10 km resolution.
We find that ICON is able to reproduce the TC frequency quite well, with about 57 hurricane-scale tropical cyclones per year compared to the observed 48 (as suggested by the "best tracks" dataset). Despite this positive bias in TC frequency, the seasonal cycle of TCs is very close to observations. A TC density map shows good agreement between model and observations, but the model tends to shift cyclone tracks slightly poleward. These differences can be attributed to different large-scale climate conditions, such as vertical wind shear and mid-tropospheric humidity. No category 5 cyclones are simulated, but the model is able to attain higher wind speeds (69 m/s) than any of the coupled climate models in the CMIP6 HighResMIP ensemble. We conclude that ICON, in its high-resolution configuration, is well suited for TC research.
How to cite: Karvinen, M., Brüggemann, N., and Marotzke, J.: Tropical Cyclones in Decadal High-Resolution Simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18104, https://doi.org/10.5194/egusphere-egu25-18104, 2025.
Tropical cyclones are impressive phenomena of tropical meteorology and form spatially highly organised structures. To shed more light on microphysical sensitivities and dynamical structure when modelling these storms, we selected the hurricane Paulette to simulate one week of the storm’s evolution with the German weather and climate model ICON in a limited area mode.
Hurricane Paulette occurred in the North-Atlantic basin in September 2020 and is the longest-lasting tropical cyclone of that year (7-22nd September).
In our experiments perturbations in the Cloud Condensation Nuclei (CCN) type and concentration are explored as well as the vertical resolution of the model. Additionally, the horizontal grid spacing is reduced to hectometre scale (300m) to get a more detailed look into the hurricane.
Here we present some key findings for the wind speed, surface pressure and cloud related variables along the hurricane track, next to how accurate the track is compared to NOAA observational data. Lastly, the influence of the introduced perturbations and reduction in resolution, horizontal and vertical, on radiation fluxes at the top-of-the-atmosphere in the simulated area is assessed. It can be stated that in most simulations the strength of Paulette is underestimated compared to the observations and the model produces to little ice to accurately represent the hurricane clouds in comparison to satellite observations.
How to cite: Cremer, R. S. and Senf, F.: Effects on the dynamical and microphysical structures of tropical storms in ICON, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6232, https://doi.org/10.5194/egusphere-egu25-6232, 2025.
Dynamics of the Atmospheric general circulation Modeled On Nonhydrostatic Domains (DYAMOND) dataset which contains nine global models that were all initialized on 1 August 2016 with the analysis from the European Centre for Medium-Range Weather Forecasts (ECMWF) and integrated for 40 days (1 August – 10 September 2016) in convection-permitting resolution. In this study, we choose one of the global models Nonhydrostatic Icosahedral Atmospheric Model (NICAMS) to study TC characteristics further.
To identify TCs in the model output, suitable TC tracking methods were attempted and adopted. It was agreed with the observation that the Western Pacific is the most TC active basin. Although the total number of TCs in DYAMOND-NICAM is similar as the observation, the fewer and more simulated TCs in Eastern Pacific and North Atlantic separately. Then, in order to study the TC structure, we fit the observation surface wind profile using Modified Rankine Vortex (MRV) wind model and get the rainfall profile from GSMAP. Compared with the observation, we found that the model simulated smaller radius of maximum wind (RMW) and rainfall (RMR) and higher peak precipitation.
Further, to study possible relationship between TC wind profile and rainfall profile, some dynamic and thermodynamic variables in the model boundary layer were used. The TC wind model in Chavas et al.(2015) was used to fit the surface wind in order to get more reseasonable TC wind profile. Then the simulated Ekman pumping transportation (TC vertical mass flux and radial mass flux) was also estimated which could be used to evaluated the precipitation transition efficiency in the model and construct the connection with TC surface wind and precipitation. We found that the accumulated Ekman pumping transportation has a great relationship (correlation efficiency nearly 0.85) with the accumulated precipitation within the TC inner core region. The results might provide some new insights to study and predict realistic and reliable TC precipitation.
How to cite: Bian, G., Masaki, S., and Tang, J.: The relationship between TC wind profile and TC rainfall profile in DYMOND-NICAM dataset, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-587, https://doi.org/10.5194/egusphere-egu25-587, 2025.
Heavy rainfall is a defining characteristic of tropical cyclones (TCs) and a significant contributor to the disasters they cause. Understanding how TC rainfall responds to climate change is critical, yet studies based on observational data remain limited compared to those relying on climate model simulations. Here, using high-resolution satellite observational rainfall data and numerical model results, we find that between 1999 and 2018, TC rain rates have exhibited contrasting trends in different regions. Globally, the TC rain rate increased by 8 ± 4%, primarily driven by enhanced rainfall in the outer regions due to increased atmospheric water vapor associated with rising surface temperatures. In contrast, the rain rate in the inner-core region of TCs decreased by 24 ± 3%, likely attributable to an increase in atmospheric stability. These findings provide valuable insights into the evolving climate characteristics of TC rainfall and their underlying mechanisms.
How to cite: Tu, S., Xu, J., and Chan, J.: Climatic Trends in Tropical Cyclone Rainfall from High-Resolution Satellite Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20415, https://doi.org/10.5194/egusphere-egu25-20415, 2025.
Using dynamic-balanced data in which tropical cyclones (TCs) are removed by the potential vorticity inversion technique, Arakane and Hsu (2021) showed that TCs significantly modulated the long-term mean state of the summer monsoon in the western North Pacific (WNP), and increased its intraseasonal variability by 50% to 70%. In order to investigate the TC impact on the global climate field, not just over the WNP, we have newly created TC removal data in which all TCs in all ocean basins are removed, rather than limiting it to TCs over the WNP region as in the previous version. In the process, improvements were also made to the potential vorticity inversion formulation to make it more suitable for removing TCs. In this presentation, we will report on the details of creating this new TC-removed data, and TC impacts on the mean fields and variability of global climate as revealed by the analysis using this data.
How to cite: Arakane, S. and Hsu, H.-H.: Dynamic-balanced global tropical cyclone removal dataset and tropical cyclone impacts on the global climate mean field and variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5455, https://doi.org/10.5194/egusphere-egu25-5455, 2025.
Sulphate Aerosol Geoengineering (SAG) works by increasing reflection of incoming solar radiation in the stratosphere and is a proposed way to mitigate global warming effects. Careful consideration of this method must include its impact on extreme weather, such as tropical cyclones. However, little to no SAG simulations exist at a resolution that is sufficient to explicitly model tropical cyclones due to the high computational cost of stratospheric chemistry. Recent work has shown a simple yet effective way to dynamically scale the stratospheric aerosol field from pre-existing SAG simulations to control global temperature, reducing the need for active stratospheric chemistry. Applying this method, we force a delayed SAG scenario in global fully-coupled CESM1 simulations with an atmosphere (ocean) grid resolution of 0.25 (0.1) degrees and compare it to a high forcing scenario. We present an examination of the impact of SAG on intensity, precipitation and track density of tropical cyclones.
How to cite: de Jong, J., Baatsen, M., and Wieners, C.: The impact of Sulphate Aerosol Geoengineering on Tropical Cyclones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18953, https://doi.org/10.5194/egusphere-egu25-18953, 2025.
Modern tropical cyclones (TCs), which originate in the tropics, feature deep warm-core symmetric structures. However, the characteristics of TCs in the early Eocene remain unclear. Here, we showed evidence from proxy data, climate modeling, and cyclone phase space that cyclones with deep warm-core symmetric structures appeared at high latitudes during the early Eocene. Under the favorable conditions of warm sea surface temperature and weak baroclinicity, most of these cyclones originated from the transition of extratropical cyclones. Meanwhile, in the tropics, only 36.91% of symmetric cyclones had a deep warm core, while 49.86% had a warm core at lower levels. These shallow cyclones tend to induce more intense rainfall than modern TCs. Our results provide unique insights into TC changes under high carbon dioxide levels and highlight the growing threat of extreme rainfall and winds associated with TCs at high latitudes.
How to cite: Zhang, T.: Contrast change of cyclogenesis over tropical and extratropical in the Eocene , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9532, https://doi.org/10.5194/egusphere-egu25-9532, 2025.
Tropical cyclones (TCs) are modulated by El Niño-Southern Oscillation (ENSO) on interannual timescales as ENSO impacts local Sea Surface Temperatures (SST) and atmospheric conditions, especially in the Pacific basin. The frequency, intensity, startup SST, windshear and life cycle of TCs vary between ENSO phases and TC seasons. Previous research focused on the Southwest Pacific (SWP) Basin has consistently shown that during El Niño phases TCs tend to form more towards the central Pacific, while during La Niña, their formation shifts towards the northeast coast of Australia. Also, TCs form more frequently during the late TC seasons than during the early TC seasons. Here, TC genesis is assessed using a Coupled ENSO index (using Niño 3.4 SST and the Southern Oscillation Index (SOI)) and a grouping into early (Oct-Jan) and late (Feb-May) TC seasons, in the decades from 1971 to 2020. We find that though the number of TCs in SWP are decreasing over the years, their SST at genesis and maximum wind speed are increasing, generating more intense TCs over the SWP basin. TCs formed during El Niño are more intense than those formed during La Niña even though there is no significant difference in their SST at genesis. We find that the threshold of environmental factors responsible for cyclogenesis in SWP are gradually changing, leading to more severe TC events in the region.
How to cite: Oginni, T., Renwick, J., and Behrens, E.: Impact of El Niño-Southern Oscillation Phases on Tropical Cyclone Genesis in the Southwest Pacific: A Study of Seasonal and Decadal Changes (1971-2020, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5295, https://doi.org/10.5194/egusphere-egu25-5295, 2025.
Recent research highlights the influence of the Atlantic Niño on the likelihood of strong hurricanes forming in the tropical Atlantic. This phenomenon increases the risk of hurricanes impacting the Caribbean islands and the United States. A recent study distinguishes two variants of the Atlantic Niño, characterized by warming concentrated in the central (CA) and eastern (EA) equatorial Atlantic, respectively. Through an analysis of observational and reanalysis data, we investigated how these two types of Atlantic Niño affect hurricane activity. The findings reveal that the CA Niño enhances hurricane frequency south of 20°N, while the CA Niña promotes hurricanes north of 20°N. The CA Niño exerts a more significant influence on hurricanes than the EA Niño, primarily by affecting wind shear, relative vorticity, and vertical velocity. In contrast, the EA Niño mainly impacts relative humidity and African Easterly Waves. These insights could improve the accuracy of seasonal hurricane forecasts.
How to cite: Wang, H., Wang, C., and Zhang, L.: Differentiated Impacts of Central and Eastern Atlantic Niño on Hurricane Activity in the Tropical North Atlantic , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2717, https://doi.org/10.5194/egusphere-egu25-2717, 2025.
This research investigates the complex dynamics of tropical cyclone (TC) formation over the North Indian Ocean (NIO), focusing on equatorial wave influences, cyclogenesis mechanisms, barotropic energy conversion, and pre-genesis evolution through high-resolution modeling. Using the severe cyclonic storm Mora (2017) as a primary case study, the research demonstrates that tropical waves play a crucial role in cyclogenesis, particularly through the interaction between Madden-Julian Oscillation (MJO) and Equatorial Rossby (ER) waves. Analysis reveals that MJO provides essential mid-level moisture while ER waves initiate low-level circulation, leading to low formation. A comprehensive composite analysis of tropical cyclones from 2017-2022 further establishes that cyclogenesis predominantly occurs during the interaction of MJO phases 2-3 and ER phases 5-7, while non-developing systems typically involve single wave or no wave interaction. The study investigates the barotropic energy conversion processes within the wave interactions, revealing how eddy kinetic energy is transferred from the mean flow to the disturbances during cyclogenesis. This energy conversion analysis provides crucial insights into why some systems develop into tropical cyclones while others remain as non-developing lows. It is observed that developing systems exhibit stronger barotropic energy conversion rates, particularly during the interaction of MJO and ER waves, contributing to the intensification of the initial disturbance.
Further, to address the challenges in early detection of tropical cyclones, this study introduces a novel stream function-based methodology for tracking quasi-closed circulation (QCC) systems before low formation. Traditional approaches using mean sea level pressure have proven insufficient for early detection. The newly developed method successfully tracked the evolution of cyclone Mora and was subsequently automated and validated across multiple seasons from 2017 onwards. This tracking algorithm demonstrates remarkable accuracy in distinguishing between developing and non-developing lows based on stream function values and amplitude differences, along with total precipitable water, achieving high accuracy. Machine learning approach is further addressed to distinguish between developing and non-developing tropical lows to tropical cyclones irrespective of different numerical model’s data.
The research extends into high-resolution numerical modeling simulation using the Model for Prediction Across Scales (MPAS-A) at 3km spatial resolution. Utilizing ERA5 initial conditions and NOAA interpolated SST data, simulations were conducted for SCS Mora over Bay of Bengal, Indian ocean. The non-hydrostatic model successfully captured pre-vortex formations and accurately simulated wind speeds and reflectivity patterns prior to low formation, providing valuable insights into the pre-genesis phase of tropical cyclones.
This comprehensive study advances our understanding of tropical cyclone formation over the NIO by establishing the critical role of wave interactions and barotropic energy conversion in cyclogenesis, developing an innovative tracking methodology, and validating high-resolution modeling approaches. The findings have significant implications for improving tropical cyclone forecasting and early warning systems in the region, particularly in identifying and tracking potential cyclonic developments prior to low pressure area formation.
How to cite: Rongmie, E., Deshpande, M., Ahire, P., and Mano Kranthi, G.: Investigation of Physical Processes Leading to the Genesis of Tropical Cyclones over the North Indian Ocean: An Integrated Study of Wave Dynamics, Energy Conversion, and Advanced Tracking Methods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-844, https://doi.org/10.5194/egusphere-egu25-844, 2025.
Predicting the intensity of cyclones a few days in advance during the formation as well as intensification of the cyclone is an open challenge. Heating from moist convection within the cyclone is considered the primary driver for the large-scale cyclonic vortex. However, the effect of interactions between small-scale vortices within the cyclone environment on the intensification of the cyclone vortex and its event-to-event variability are poorly considered. To enable skilful cyclone predictions, it is essential to first understand the local interactions in the atmosphere that facilitate self-sustained rotation and updraft of moist air.
We present a novel approach using complex networks to study atmospheric interactions and identify vortical perturbations that influence the formation of a depression and eventually a cyclone. We analyze the atmospheric flow over the Bay of Bengal (BoB) during different category-5 cyclones, namely, Amphan (2020), Sidr (2007) and Bangladesh (1991). Relative vorticity is obtained at hourly temporal resolution from the ERA5 reanalysis dataset (ECMWF reanalysis project). Nodes are locations between the equator to 30°N and 75°E to 105°E with a spatial resolution of 0.5°. We construct time-varying networks where each network corresponds to a short time period of 29 hours. Consecutive networks are separated by a difference of three hours. In each network, links are established between two nodes if (i) the time series of relative vorticity at both locations are correlated in a 24-hour window with a maximum of five-hour lag, and (ii) the two nodes are in spatial proximity of 2° latitude-longitude width centred at any one of the nodes. Note that, the spatial proximity is approximately 200 km that is comparable to the gale force wind radius of category-5 cyclones in BoB.
Through this approach, we decipher the relation between the local flow interactions and the global emergence of order in the form of a cyclone in the atmosphere. Regions of high connectivity in the network represent patches of locally coherent vorticity dynamics. Multiple such patches emerge throughout the life of a cyclone. Initially, these patches revolve around a developing low-pressure system, merging and intensifying the low-pressure system into a tropical depression and eventually into a tropical cyclone. Our approach helps identify prominent mesoscale convective systems that can form away from the low-pressure system but are entrained towards the depression and help intensify the storm at different stages.
Next, we use Broadcast Mode Analysis (BMA), an advanced tool to identify the critical nodes that influence information propagation in time-varying networks. The analysis reveals nodes (locations) from where the most influential patch of coherent vorticity dynamics emerges that will eventually propagate, merge with and intensify the storm. We find the most influential region (the broadcast mode) and the most influenced region (receiving mode) in every 56-hour period corresponding to 10 networks. The receiving mode of one 56-hour period is approximately similar to the broadcast mode of the next 56-hour period. Broadcast mode analysis highlights the potential of tracking local interactions and mesoscale patches of coherent vorticity dynamics to improve the prediction of cyclone intensity.
How to cite: Tandon, S., Singh, A., Goswami, B. N., and Sujith, R. I.: Complex networks to identify the merging of patches of coherent vorticity dynamics during tropical cyclones in the Bay of Bengal , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1771, https://doi.org/10.5194/egusphere-egu25-1771, 2025.
Tropical easterly waves (TEWs) are westward-moving waves often within trade winds but occurs ubiquitously in tropics and play a significant role in the genesis of tropical cyclones (TCs). They are well-known as primary precursors of TCs in the Atlantic, yet their global relationship with TCs has been less explored. This study, for the first time, presents the global distribution of TEW activity using a combined thermodynamic and dynamic framework, based on 6-hourly Outgoing Longwave Radiation and curvature vorticity. We then demonstrate that TEWs play a dominant role in approximately 23–71% of global TC genesis, with their highest impacts in the North Atlantic (71%) and Western Pacific (54%). We further identify that TEWs, in its general coupling with TC genesis dynamics, act to intensify TC convection and vorticity in all TC main development regions, albeit the vorticity enhancement is relatively weaker in the North Atlantic. To understand the basin differences in this general TEW-TC relationship, we further investigated background conditions for TC genesis in each basin and found an additional dry environment constraint in the Atlantic TC genesis, yet still delineating the critical role of TEWs in TC development.
How to cite: Du, X., Chu, J.-E., Jin, F.-F., and Cheung, H. M.: Global coupled dynamics of tropical easterly waves and tropical cyclone genesis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-192, https://doi.org/10.5194/egusphere-egu25-192, 2025.
Mesoscale convective processes and related dynamic/thermodynamic responses may play an important role in the Tropical Cyclone (TC) genesis, in addition to the favorable environmental conditions. The objective of this study is to determine whether and how unique are mesoscale organizations and convective properties of tropical disturbances prior to TC formation in the Northwest Pacific. Previous studies with a similar goal are based on either a small sample size or limited observational source (e.g., only Infrared). This study identifies over 3000 episodes of developing (Dev) and nondeveloping (Nondev) tropical disturbances and utilizes a large amount of multi-source satellite observations (precipitation, infrared, microwave, spaceborne radar, etc.) to comprehensively compare their convective structures. The Dev and Nondev disturbances were borne in similar large-scale environments such as SST, low-level vorticity, vertical wind shear, except that the Dev tropospheric conditions are slightly moister. However, the frequency, organization, intensities, and ensemble microphysics of the convection are significantly different between Dev (48-96h prior to TC formation) and Nondev. Both Dev and Nondev show very asymmetric distributions of convection with maxima in the down-shear quadrants, but Dev systems have greater areas of precipitation and cold clouds. The embedded individual convective systems of Dev are also more organized, i.e., greater areas and higher stratiform rain fraction. Furthermore, Dev convection is stronger and present greater ice-phase content as indicated by both the passive microwave and spaceborne measurements. Interestingly, Dev disturbances also have markedly higher frequency of shallow warm convection, especially in the up-shear regions, which may help moistening the lower-to-middle troposphere and beneficial for further deep convective developing. In most of the Dev storms, convection rapidly become more organized and deeper during 24-48 prior to the TC genesis. This study further compares the organization and convective properties among Dev systems generated under different types of large-scale flow pattern such as monsoon trough and easterly wave.
How to cite: Zhang, Z. and Xu, W.: Mesoscale Organizations and Convective Properties of Developing and Nondeveloping Tropical Disturbances over the Northwest Pacific Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14555, https://doi.org/10.5194/egusphere-egu25-14555, 2025.
Understanding precipitation variability and extremes in Equatorial East Africa is vital for ensuring water and food security and mitigating the socioeconomic consequences of extreme events. Previous research has shown that sub-seasonal precipitation variability in this region is closely related to the wind direction, with precipitation more probable on days where the wind blows anomalously from the west, advecting moisture from the Congo basin. However, the exact nature of the westerly circulation and the conditions under which it forms are not fully understood. Here, we present a multi-decadal analysis of East African westerly winds. We use methods developed from studies of atmospheric rivers to objectively identify “westerly moisture transport events” (WMTEs), facilitating new insights into the seasonal distribution and importance of these westerlies, the regions within Eastern Africa where they occur, and the role of both the Madden-Julian Oscillation and tropical cyclones in their development. Finally, we also investigate the role of WMTEs as drivers of regional sub-seasonal precipitation variability.
How to cite: Peal, R. and Collier, E.: A multi-decadal analysis of westerly moisture transport events (WMTEs) in Equatorial East Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-877, https://doi.org/10.5194/egusphere-egu25-877, 2025.
The moist margin is a sharp gradient of humidity that separates the moist deep tropics from the drier subtropics, and as such its movement is important for describing rainfall variability. In this work, we investigate how weather systems are related to synoptic variability in the moist margin. We use an object-based approach to relate moist margin perturbations to convectively coupled equatorial waves, the Madden-Julian Oscillation (MJO) and monsoon low-pressure systems (LPS). We also consider extratropical interactions with the moist margin, which are defined through upper-level potential vorticity (PV) anomalies. The results indicate that the MJO and equatorial Rossby waves have significant modulating effects on the moist margin. In comparison, monsoon LPS are infrequent but strongly influence the moist margin when they occur. The largest and longest-lived perturbations are commonly related to PV anomalies, and their composite structure reveals a clear wave-like signal, often with anticyclonic PV anomalies near the perturbed margin and cyclonic PV anomalies remotely. Open questions remain regarding the potential two-way interactions and feedback mechanisms between extratropical PV anomalies and the moist margin, which are examined here in some detail.
How to cite: Robinson, C., Narsey, S., Jakob, C., and Nguyen, H.: Synoptic variability in the moist margin and its connection to tropical and extratropical weather systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1450, https://doi.org/10.5194/egusphere-egu25-1450, 2025.
We investigate the projected changes to the location, width and intensity of the intertropical convergence zone (ITCZ) in two global 30-year coupled storm resolving simulations, evolving under the shared socioeconomic pathway 3.7-0 forcing. The first simulation performed using the storm resolving version of the ICOsahedral Nonhydrostatic model, ICON-Sapphire, resolves convection explicitly and employs a horizontal resolution of 10 km in the atmosphere and 5 km in the ocean. The second simulation performed using the Integrated Forecasting System coupled to the Finite-volumE Sea ice-Ocean Model (IFS-FESOM), utilizes a convective parameterization with reduced cloud base mass flux and has a similar horizontal resolution as the ICON-Sapphire simulation (9 km in the atmosphere and 5 km in the ocean).
The magnitude of warming over 30 years is about 1K in ICON-Sapphire and 2K in IFS-FESOM. Changes in the seasonal mean ITCZ positions, determined from the latitude of maximum precipitable water in [30°S, 30°N], are not substantial in both the models, except in IFS-FESOM during boreal spring where a southward shift is seen in the Central Pacific basin. Monthly anomalies in the ITCZ latitude also show a southward shift in IFS-FESOM. Trends in the ITCZ width, computed based on the moist margins of the tropics, and ITCZ intensity, determined using precipitation in the ITCZ latitudes, are also analyzed.
How to cite: Praturi, D. S. and Hohenegger, C.: Projected changes to the intertropical convergence zone in warming scenario global storm resolving simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10328, https://doi.org/10.5194/egusphere-egu25-10328, 2025.
The Cabo Verde region is subject to the activity of many tropical waves during the boreal summer. They are known to favour or inhibit convective activity, and to play a role in the formation of Tropical Cyclones. A frequency-wavenumber filtering method is used to identify the different waves. A novel tracking protocol is used to distinguish African Easterly Waves propagating north and south of the African Easterly Jet based on their frequencies within the Mixed-Rossby Gravity - Tropical Disturbance (MRG-TD) domain, labeled MRG-TD1 and MRG-TD2, respectively. Based on in-situ and satellite measurements from the Cloud Atmospheric Dynamics Dust Interactions in West Africa (CADDIWA) campaign which took place in Cape Verde in September 201, the impact of each tropical type on the atmosphere vertical structure and dust content is discussed. Our results show that Equatorial Rossby waves mainly impact thermodynamics above 750 hPa, while MRG-TD1 affect jet-level thermodynamics, and MRG-TD2 modulate moisture in the lower troposphere. Dust event are mainly driven by MRG-TD2. The importance of the interaction between waves for tropical cyclogenesis is also highlighted which provides new outlooks for improving tropical cyclogenesis forecasting in the region.
How to cite: Jonville, T., Borne, M., Flamant, C., Cuesta, J., Bock, O., Bosser, P., Lavaysse, C., Fink, A., and Knippertz, P.: Impact of tropical waves on the atmospheric structure and composition above Cabo Verde during the CADDIWA campaign , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4145, https://doi.org/10.5194/egusphere-egu25-4145, 2025.
Satellite-based climatological analyses show a sharp contrast between the fractional convective and stratiform rainfall over Africa and its neighboring eastern Atlantic water. While convective rainfall dominates over continental Africa, stratiform precipitation dominates the rainfall totals over the eastern Atlantic. The convective maximum over land is mainly contributed by numerous mesoscale convective systems (MCSs). At the same time, the diurnal peak of precipitation exhibits a maximum just offshore from western Africa. To this end, the objective of this study is to use a phenomenon-based approach to investigate the sharp rainfall morphology contrast between continental Africa and the eastern Atlantic while also relating that contrast to the climatological precipitation maximum off western Africa. We hypothesize that MCSs coming off Africa structurally change as they move off continental Africa and into the maritime environment over the Atlantic. To test this hypothesis, we use primarily hindcasts produced during NASA’s Convective Processes Experiment - Cabo Verde (CPEX-CV) field campaign using the Model for Prediction Across Scales - Atmosphere (MPAS-A). This model was configured with a convection-permitting mesh extending from eastern Africa to the western Atlantic, thus covering the extensive tracks of multiple MCSs as they propagated offshore into the Atlantic. Results show that MCSs in MPAS-A transition from mature trailing stratiform systems over land to decaying stratiform systems over water. Further analysis will investigate if shear-cold pool dynamics can explain this behavior, and how such dynamics change with the time of day.
How to cite: Rios-Berrios, R., Sakaeda, N., Martin, E., and Wu, S.-N.: Convective-to-Stratiform Transition of MCSs off Western Africa and its Relationship to the Diurnal Offshore Precipitation Maximum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12499, https://doi.org/10.5194/egusphere-egu25-12499, 2025.
The large islands of the Maritime Continent experience a strong diurnal cycle, with enhanced convection and precipitation over land through the afternoon and evening. Convective storms that initiate over land may then propagate out over surrounding coastal waters overnight; the land breeze is typically assumed to drive the overnight convergence of moisture offshore, however some of the offshore moisture convergence may also be attributed to other density current drivers, such as cold pools.
A regional configuration of the MetUM over southwest Sumatra has been used to isolate the influence of cold pool dynamics on the development of the diurnal cycle for three case study days by switching off precipitation re-evaporation (thereby preventing cold pool formation), and these results are compared with control runs with precipitation re-evaporation enabled.
This presentation will offer insight into the contribution of cold pools to offshore propagation of convective storms under different large-scale conditions, and into the influence of model resolution on how well this contribution is resolved.
How to cite: Mustafa, J., Birch, C., Marsham, J., Burns, H., and Peatman, S.: Cold pool contribution to the development of convective storms over southwest Sumatra: insights from sub-km modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2162, https://doi.org/10.5194/egusphere-egu25-2162, 2025.
Due to its vast size, Lake Victoria in East Africa significantly impacts the region’s climate through lake breezes, which influence convective activity, and thus precipitation, as well as air pollution and quality in coastal cities. These breezes, with their leading edges known as lake-breeze fronts (LBF), affect local and regional weather by initiating deep moist convection, even during the dry months of December-February (DJF) and June-August (JJA). This can lead to heavy precipitation inland or over the lake, resulting in weather-related disasters and losses. Despite their importance, there is limited research on LBFs linked with Lake Victoria. To address this gap, we developed a novel algorithm to detect LBF passages, mainly focusing on the shorelines of Uganda. We leveraged 15-minute observations from 44 automatic weather stations from the Trans-African Hydrometeorological Observatory (TAHMO) and Uganda National Meteorological Authority (UNMA) over six years (2017-2022).
Our objective observation-based lake breeze detection algorithm (OLBDA) identifies LBF passages using wind speed and direction, temperature, dew point, and precipitation measurements from stations. We focused on daytime periods (0900 – 1900LT) when the coastal land-lake temperature contrast is strongest, specifically during the dry months. The algorithm employs three criteria to detect LBF passages at any given station. First, OLBDA checks for a rapid wind reversal from offshore (relative to the nearest coastline) to onshore, or a rapid increase in wind speed within defined onshore directions. If the wind criterion is met, the data are then tested for a drop in air temperature and an increase in dew point. Here, percentile-based thresholds for temperature and dew point criteria are applied to account for regional variabilities. Lastly, to avoid false detections caused by precipitation-induced temperature drops and wind shifts, a 3-hour precipitation amount < 0.1mm at a station before the LBF passage is required. If all criteria are met, that day is considered a lake-breeze day at that station.
To test the performance, we compared the OLBDA-detected lake-breeze days with manually identified lake-breeze days (“ground truth”) within the study period from NASA’s satellite visible spectrum (Terra- and Aqua-MODIS, and NOAA-20). The algorithm detected more than 70% and 60% of the total cases identified from satellite images for coastal (within 2 km) and semi-coastal (2-10km) stations respectively, indicating good performance.
Preliminary results show that most LBF passages occur from afternoon to late evening, peaking at 1300LT for coastal stations and shifting with the station's distance from the coastline. The majority of detected lake-breeze days occur during the DJF months, with January having the most detected days. Other lake breeze characteristics including the onset and cessation time, strength, duration, propagation speed and time, and inland penetration depth, are being examined.
Finally, we aim to develop a detailed year-round observed Lake Victoria breeze climatology over Uganda. Our findings can serve as an observational benchmark to (a) improve understanding of this phenomenon’s impact on the local climate and communities along the northern shores of Lake Victoria, and (b) validate numerical simulations of lake breezes over the region.
How to cite: Ssemujju, M., Maranan, M., and Fink, A. H.: A novel algorithm for detecting Lake Victoria's lake-breeze fronts from station observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8947, https://doi.org/10.5194/egusphere-egu25-8947, 2025.
Humid heatwaves (HHWs) can cause heat stress in humans by reducing the ability to sweat in higher humidity. West Africa is an area of high interest due to its rapid population growth, high vulnerability, and latitudinal variation in HHW drivers. There is little understanding in how HHWs are triggered at synoptic scales. Using reanalysis and satellite-derived rainfall, we find different drivers in the three key regions of the Guinean coast, Sahel and Sahara. HHWs are associated with elevated near-surface specific humidity in all three regions. Near-surface temperature is also elevated in the Guinean Coast and Sahel regions while the Sahara region experiences a decrease during events. The rise in both temperature and humidity can be explained by the combination of increased near-surface downward shortwave radiation and trapping of moisture in the lower troposphere. The main moisture source is rainfall two days prior. After rainfall, clearer skies brought by dry mid-tropospheric northeasterly winds drive increased shortwave radiation, providing energy for surface evaporation and increasing temperature. In the Sahara region, the background air temperature is already very high, so there is enough energy for surface evaporation despite the mitigating impact of rain on temperature, indicated by the increase of surface latent heat flux to the atmosphere by as much as 118%. African Easterly Waves (AEWs) are a key driver of rainfall in Sahel and Sahara regions, and, therefore, are also a source of HHW predictability. The probability of a HHW increases during an AEW passage by as much as 24% in Western Sahara, which contains major population centres of over 1 million people. We also find most HHW events occur south of the intertropical discontinuity, which moves north and south with the onset and cessation of the African monsoon. While the majority of HHW events occur during the African Monsoon season in the Sahara, most events occur immediately before and after the start of the monsoon season further south. In addition, we analyse vertical profiles of cloud from CloudSat and CALIPSO, and show a clear anomaly from climatology during HHWs, with reduced cloud in the moister Guinean coast and Sahel to the south and increased cloud associated with rain in the more arid region of the Sahara. Understanding of the drivers and predictability of HHWs is important for risk management and adaptation measures such as the development of early warning systems.
How to cite: Law, J., Birch, C., Jackson, L., Bouniol, D., Bollasina, M., and Marsham, J.: Synoptic drivers of humid heatwaves in West Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6289, https://doi.org/10.5194/egusphere-egu25-6289, 2025.
How to cite: Hottovy, S., Camacho, M., and Flatau, M.: Diurnal Cycle Effects over the Maritime Continent on Tropical Waves Using a Simple Linear Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6816, https://doi.org/10.5194/egusphere-egu25-6816, 2025.
A mechanism for the interannual variability of the Madden–Julian Oscillation (MJO) realization frequency is examined. Based on the number of active days of MJO events detected using the tracking method for the Real-time Multivariate MJO Index, we quantify the year-to-year variability in the initiation and propagation of boreal-winter MJOs. Active years of MJO realization (MJO-A) are characterized by more frequent MJO initiation, leading to complete propagation into the western Pacific (WP), whereas this is less common in inactive years (MJO-IA) due to stronger advective drying and the resultant hindrance of column moistening over the WP. This contrast is linked to differences in boreal-winter mean convection and circulations: MJO-A (MJO-IA) years are characterized by enhanced and suppressed (suppressed and enhanced) convection over the WP/IO and Maritime Continent (MC), respectively. This modulation is driven by the combined effects of the El Niño-Southern Oscillation (ENSO) and the quasi-biennial oscillation (QBO). During moderate-to-strong El Niño events, MJO realization manifests actively regardless of QBO phase or amplitude, unless additional convective suppression occurs in the eastern Indian Ocean and/or MC due to other forcings, such as a positive Indian Ocean Dipole. In contrast, during ENSO-neutral and La Niña conditions, stronger QBO easterly phases tend to favor MJO realization, independent of ENSO. This QBO–MJO connection (except during El Niño conditions) is due to the zonal heterogeneity of QBO impacts; changes in the seasonal mean static stability near the tropopause over the WP modify the mean convective activity in that region. The zonal heterogeneity and ENSO phase-dependency of QBO impacts are interpreted by focusing on the vertical propagation of the Kelvin wave structure over the MC, influenced by both QBO winds and background Walker circulations.
How to cite: Takasuka, D., Kohyama, T., Suematsu, T., and Miura, H.: Cooperative effects of QBO and ENSO on controlling the favorableness of the MJO realization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18495, https://doi.org/10.5194/egusphere-egu25-18495, 2025.
Kelvin waves play an important role in tropical circulation variability. Previous research has shown that the tropospheric Kelvin wave activity is associated with both tropical convection and dry dynamics, which can be connected to the extratropics. The relative importance of the adiabatic and diabatic processes for Kelvin wave energy tendencies has not yet been consistently evaluated in reanalysis data.
In this study, we investigate the Kelvin wave energy budget focusing on the relative contributions of physical and dynamical processes in ERA5 reanalysis data. Kelvin waves and their energy tendencies are identified by applying three-dimensional normal-mode function decomposition. A novel aspect of our method is that momentum and temperature tendencies are computed directly from the complex normal-mode function expansion coefficients. This allows to quantify the adiabatic energy tendencies as nonlinear interactions of Rossby and inertia-gravity waves and the zonal mean flow. The diabatic energy tendencies are determined from the momentum and temperature tendencies due to parametrizations in the short-term ERA5 forecasts.
The most relevant results are that the advection of zonal momentum is on average a source of Kelvin wave energy, whereas Kelvin wave energy variability on diurnal and submonthly scales is mainly due to heating by shortwave radiation and latent heat forcing, respectively. The 3D normal-mode decomposition allows to reveal the roles of wave-wave and wave-mean flow interactions in dynamical processes, in particular in the tropics.
How to cite: Holube, K. M., Lunkeit, F., Vasylkevych, S., and Žagar, N.: Adiabatic and diabatic energy tendencies of the equatorial Kelvin wave, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7183, https://doi.org/10.5194/egusphere-egu25-7183, 2025.
Extratropical disturbances are known to impact the genesis and intensification of Mixed Rossby-Gravity waves (MRGW) in the Western Hemisphere (WH). The study provides observational evidence supporting the wave resonance (WR) theory which attempts to explain the intensification of MRGW by extratropical forcing. Wavenumber-frequency cospectral analysis and a bulk measure of growth of MRGW estimated using reanalysis data reveal that the extratropical forcing manifested in the form of eddy momentum flux convergence can create eddy kinetic energy (EKE) and aid the intensification of MRGW via WR mechanism during boreal winter season. However, the WR mechanism does not hold during boreal summer season as the extratropical forcing tends to dampen the MRGW. The analysis also reveals that the Doppler-shifted eastward propagating MRGW in the WH during boreal winter season are not maintained by extratropical forcing, marking another highlight of this study.
How to cite: Mehak, M. and Ettammal, S.: Wave Resonance Induced Intensification of Mixed Rossby-Gravity Waves by Extratropical Forcing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-589, https://doi.org/10.5194/egusphere-egu25-589, 2025.
This work is a second part contribution of the effect of intraseasonal oscillations on precipitation over the study region. The index generated for each wave (Part I) allow to classify events like convection inhibiting (dry) and convection favoring (wet) days and correlate with precipitation data from ERA5 and CHIRPS. Results show positive and negative precipitation anomalies across the region associated with each oscillatory process, which can be linked to anomalies in moisture transport and convection within the atmospheric column. During wet days, the Tropical Easterly Waves contribute up to 20% of precipitation over Caribbean Sea and eastern Pacific (and western Mexico), while the Kelvin waves accounts for 15% over the tropical eastern Pacific. On the other hand, Mixed Rossby-Gravity waves accounts for 15% of precipitation over the eastern Pacific (10°N - and western Mexico) during wet days and, 12% of precipitation on the Pacific coast of Central America during dry days. Finally, the Madden-Julian Oscillation contributes nearly 15% of precipitation over the Pacific coast of Mexico and Central America during wet days. These findings offer new insights into the spatial and temporal patterns within the region related to these intraseasonal oscillations.
How to cite: Yepes, J., Builes, A., Salas, H., Valencia, J., Rivera, P., Carmona, A., and Bedoya, M.: Intraseasonal Oscillations and hydroclimate of Northern South America, Central America and Mexico (Part II: Effects on precipitation), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-559, https://doi.org/10.5194/egusphere-egu25-559, 2025.
The contribution of intraseasonal variability (10- 90 days) in OLR data across Northern South America, Central America, and Mexico was studied. This variability is driven by planetary and tropical oscillations, including Kelvin waves, Tropical Easterly Waves, Mixed Rossby-Gravity Waves, and the Madden-Julian Oscillation, which display distinct signals in the wavenumber—frequency power spectra. Using the Wheeler-Kiladis methodology (1999) and the spatial EOF analysis for local activity index and composites by Mounier (2007), our findings reveal that intraseasonal variability accounts for 10% to 35% of the total variance, depending on the specific location, with Kelvin waves being the largest contributors to the OLR variance in the study region. This methodology allows to propose a local index for each coupled convective wave aiming to classify as convection inhibiting (dry) and convection favoring (wet) days events. The annual cycle of these dry and wet events for each wave show interesting patterns like a predominance of Tropical Easterly Waves and Mixed Rossby-Gravity Waves during the boreal summer and major Kelvin waves occurring during May and April.
How to cite: Builes-Jaramillo, A., Yepes, J., Salas, H. D., Bedoya-Soto, J. M., Rivera, P., Valencia, J., and Carmona, A. M.: Intraseasonal Oscillations and hydroclimate of Northern South America, Central America and Mexico (Part I: The identification process), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-663, https://doi.org/10.5194/egusphere-egu25-663, 2025.
Currently, the Monte Carlo Method is commonly used to estimate the uncertainty of tropical cyclone (TC) track forecasts. By performing random sampling of both along-track and cross-track errors, the potential range of official forecast errors is estimated (DeMaria et al. 2009; Tsai et al. 2011).
This study utilizes a Recurrent Neural Network (RNN) with an Encoder-Decoder architecture to represent situation-dependent track forecast uncertainty and the spatiotemporal correlations of forecast errors. The datasets used in this study include the Central Weather Administration’s (CWA) official TC track forecasts from 2018 to 2022, as well as deterministic and ensemble track forecasts from global numerical weather prediction models, specifically ECMWF and NCEP models.
Preliminary results indicate that the RNN-based approach reasonably reflects potential error ranges under different scenarios. For instance, TCs located at mid-to-high latitudes with higher translation speeds usually exhibit smaller cross-track forecast errors. Additionally, the prediction intervals (PIs) derived in this study can reasonably cover the proportion of observed data: the uncertainty ranges of the mean +/- one (two) standard deviations encompass approximately 70% (95%) of observed data. Furthermore, large-scale environmental indices (e.g., steering flow and monsoon circulation) are considered to further reduce the uncertainty of TC track forecasts. More detailed findings will be presented during the meeting.
How to cite: Lin, F.-Y. and Tsai, H.-C.: Improving Situation-Dependent Uncertainty Estimation in Tropical Cyclone Track Forecasts Using Encoder-Decoder Neural Networks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2416, https://doi.org/10.5194/egusphere-egu25-2416, 2025.
Some of Tropical Cyclones undergo a rapid intensification process, which causes them to become stronger typhoons. Rapid Intensification (RI) is defined as the increase in maximum sustained winds to 30 kt (15 m/s) or more within a 24-hour period (Kaplan and DeMaria, 2003). Typhoons that have undergone RI mainly strengthen into strong LMIs, which can cause significant damage in a relatively short period of time. The recent increase in the number of cases of RI of Tropical Cyclones has highlighted the importance of advanced forecasting. However, achieving accuracy in these forecasts remains a significant challenge. In general, the intensity of typhoons is highly dependent on thermal conditions, such as ocean temperatures. However, the process of rapid intensity development is complex and influenced by dynamic factors, such as upper-level divergence and vertical wind shear. In this study, we developed a guidance for predicting the probability of rapid intensity development in a typhoon using environmental prediction factors at the time of its occurrence. For the purpose of supporting KMA's typhoon forecasting, a statistical based prediction model for the probability of RI was developed and evaluated from 2023 to 2024. It uses logistic regression to provide RI predictions up to the next 24 hours and 48 hours. The predictor variables included upper-level divergence, relative humidity, equivalent potential temperature (EPT), depth-averaged temperature (DAT), tropical cyclone heat potential (TCHP), thermodynamic net energy gain rate (NGR) (Lee et al., 2019), and 30 kt wind radius. To evaluate the accuracy of predictions for typhoons that occurred between June and November 2021-2023, 12 cases of RI and 42 cases of non-RI were analyzed. The POD was 0.78 and 0.76 for the 24-hour and 48-hour prediction accuracy, respectively, with corresponding FAR of 0.32 and 0.38. Predictive models showed good results during the validation period, but predicting favorable conditions for RI is still complex and challenging.
How to cite: Lee, H., Kim, J., Won, S., and Lee, H.: Probabilistic Predictions on TC Rapid Intensification, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3022, https://doi.org/10.5194/egusphere-egu25-3022, 2025.
Convective clouds play a vital role in Earth's hydrological cycle. In the tropics, these clouds often form extensive, spatially connected structures known as mesoscale convective systems (MCSs). MCSs are significant contributors to severe weather and are linked to potential changes in precipitation extremes. However, they are still connected to uncertainties, particularly regarding the intensity and variability of their spatio-temporal clustering (convective organisation).
This study aims to characterise regional patterns of convective organisation and explore their connections to convective cloud microphysics. The analysis covers a region in tropical Africa between 30° W – 30° E and 30° N – 30° S with a focus on the spring-to-summer period. Convective clouds and the intensity of their organisation are detected using 3D radar reflectivities. These spatio-temporal contiguous predictions are derived through a machine learning (ML) based extrapolation of observations from passive (MSG SEVIRI) and active (CloudSat) 2D remote sensing sensors. Furthermore, three organisation indices are used to quantify the organisational state of the atmosphere. They are leveraged to examine the relationship between convective cloud development and large-scale organisation. Using an object-based algorithm, we identify convective core and anvil regions in the predicted 3D radar reflectivities at each time step. These cloud objects are tracked over time to construct seamless 4D trajectories that capture cloud movement in three dimensions. Then, we calculate the indices to characterise the degree of organisation at each time point. The study evaluates regional statistics for convective organisation and analyses the key features of the observed systems.
Our findings highlight regional hotspots of convective organisation over the Gulf of Guinea, continental West Africa, and the Atlantic Ocean. These areas frequently host long-lasting, highly active cloud systems, such as MCSs. We observe seasonal variations in convective cloud development lead to a modest 5 % increase in organisation during summer. For example, differences in landmass distribution and the influence of extratropical dynamics in the southern hemisphere contribute to greater variability compared to the northern hemisphere. Over the ocean, organisation indices are approximately 5–10 % higher than over land. Overall, the results highlight the importance of regional characteristics in assessing convective organisation. Integrating data from multiple remote sensing instruments offers valuable insights, potentially enhancing climate risk assessments. However, our study emphasises that the overlapping effects of isolated and clustered convection may impact the statistical analysis. Addressing this issue requires an adapted organisation index.
How to cite: Brüning, S. and Tost, H.: A ML-based perspective on spatio-temporal patterns of convective organisation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3055, https://doi.org/10.5194/egusphere-egu25-3055, 2025.
Accurate forecasting of tropical cyclones is crucial for safeguarding coastal areas against the loss of life and property. Near-real-time analysis data, such as the Cross-Calibrated Multi-Platform Ocean Surface Wind Vector (CCMP), is widely utilized for predicting tropical cyclones due to its comprehensive coverage and consistent temporal and spatial measurements. However, CCMP has a limited resolution of 25 kilometers and frequently underestimates wind speeds during tropical cyclones because of rain interference. In contrast, Synthetic Aperture Radar (SAR) can measure ocean surface winds under all weather conditions with a significantly higher resolution of approximately 0.5 kilometers, though it lacks extensive area and temporal coverage. We developed a novel deep learning approach that leverages the strengths of both CCMP and SAR data. By using SAR wind measurements for tropical cyclones globally as the ground truth, we trained our deep learning model on the corresponding CCMP data to enhance its accuracy and spatial resolution. We evaluated various deep learning architectures, including U-Net, DeepLabV3+, and TransUNet. Our results indicate that TransUNet performs the best, improving CCMP's accuracy by 45% for wind speeds over 20 m/s, 20% for overall wind field, 56% for the maximum wind speeds, and 64% for the radius of the maximum wind speed. Our method can create gap-free, high-resolution, and accurate ocean surface wind data for tropical cyclones.
How to cite: Zhang, E., Su, H., and Chan, P.-W.: Deep Learning-based Fusion of Analysis and Satellite Measurements for Ocean Surface Wind Downscaling for Tropical Cyclones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3457, https://doi.org/10.5194/egusphere-egu25-3457, 2025.
The organization of tropical deep convection is supported by radiative feedbacks, in which high clouds and moisture anomalies associated with convection imposes anomalous longwave (LW) radiative heating in the atmosphere, further supporting convection. Despite an abundance of studies with numerical simulations, the interactions between tropical convective organization, radiative feedbacks, and the large-scale atmospheric environment have not been examined comprehensively using observations. This presentation examines such interactions among tropical mesoscale organized convection, radiative feedbacks, and the Madden-Julian oscillation (MJO) using a set of observation-derived data products, including retrievals using spaceborne satellites, ground-based precipitation radar, and reanalyses. The results of this analysis demonstrate that: (1) Higher sea surface temperature and stronger low-level wind shear strength enhance tropical mesoscale convective activity, increasing cirrus cloud cover and LW heating generated per unit precipitation. (2) The estimation of LW cloud-radiative feedback (LW CRF), defined as the LW cloud-radiative heating produced per unit precipitation, is sensitive to the precipitation data set used. (3) Radiatively driven circulations and the associated moistening effects in the MJO can be derived in a weak-temperature-gradient framework and a linear baroclinic model. LW heating moistens the MJO more efficiently than the total apparent heat source, while shortwave (SW) radiative effects dry the MJO. (4) The LW CRF of the MJO is spatially inhomogeneous, with stronger feedbacks over the tropical Indian ocean and to the northwest of Australia, but weaker feedbacks over the tropical western and central Pacific. The spatial pattern may be determined by the spatial distribution of preferred convective types and precipitation efficiency.
How to cite: Maloney, E. and Hsiao, W.-T.: Radiative feedbacks in the Madden-Julian oscillation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3781, https://doi.org/10.5194/egusphere-egu25-3781, 2025.
The formation of a vertically aligned vortex is essential for the intensification of tropical cyclones (TCs), particularly under conditions of environmental vertical wind shear (VWS). This study investigates the physical mechanisms driving vortex tilt evolution in two simulated TCs subjected to environmental shears of 6 m s⁻¹ and 10 m s⁻¹. Our findings indicate that balanced dynamics play a pivotal role in governing vortex tilt. Specifically, the tilt-induced distortion of isentropic surfaces generates negative virtual potential temperature anomalies on the downtilt side and positive anomalies on the uptilt side of the vortex. As air parcels undergo cyclonic rotation along these distorted isentropic surfaces, they ascend on the right side of the tilt vector, resulting in increased relative humidity and eventual saturation. This leads to diabatic ascent and enhanced convection in the downtilt and downtilt-left quadrants, which amplifies the wavenumber-1 circulation through convectively coupled vortex Rossby waves, further modifying the vortex tilt. This study underscores the importance of balanced dynamics in understanding the interplay between vortex tilt, wavenumber-1 structures (Rossby waves), and convective asymmetries in the intensification of tropical cyclones under vertical wind shear.
How to cite: Wu, L. and Zhou, X.: Balanced Evolution of the Vertical Tilt of Simulated Tropical Cyclone Vortices in a Sheared Environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3913, https://doi.org/10.5194/egusphere-egu25-3913, 2025.
Long-lasting La Niña events (including double-year and triple-year La Niña events) have become more frequent in recent years. How the multi-year La Niña events affect tropical cyclone (TC) activities in the western North Pacific (WNP) and whether they differ from single-year La Niña events are unknown. Here we show that TCs are more active over the far-WNP (FWNP, 110°–150°E), leading to marked high risks at China coasts during the second decaying summer of double-year La Niña events. The anomalous TC activities are directly related to the enhanced cyclonic anomaly over the FWNP, possibly a result of large-scale remote forcing initiated by the tropical North Atlantic (TNA) cooling. The persistent TNA cooling from the decaying winter to summer of double-year La Niña events drives westerlies over the Indo-western Pacific through Kelvin waves, which induce the cooling over the north Indian Ocean via the wind-evaporation-sea surface temperature effect, favoring the asymmetric heat distribution pattern and stimulating an anomalous vertical circulation over the eastern Indian Ocean to FWNP. The cooling over the north Indian Ocean also excites Gill responses, magnifying the TNAinduced westerlies and boosting the anomalous vertical circulation, and thus gives rise to the strong cyclonic circulation anomaly over the FWNP in summer. We suggest that the key point of the process is the strong TNA cooling related to the persistent negative Pacific-North American pattern (PNA) and positive North Atlantic Oscillation (NAO) while double-year La Niña events decay, distinct from the rapid decline of PNA and NAO during single-year La Niña events. The work provides a unique perspective on understanding TC activities over the WNP related to the El Niño-Southern Oscillation.
How to cite: Luo, X., Yang, L., Chan, J. C. L., Chen, S., Peng, Q., and Wang, D.: China coasts facing more tropical cyclone risks during the second decaying summer of double-year La Niña events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4206, https://doi.org/10.5194/egusphere-egu25-4206, 2025.
Tropical cyclones (TCs) pose a significant threat to coastal populations and ecosystems. To effectively mitigate TC risk, it is essential to understand their evolution under current and future climate conditions. One aspect of their development that remains unclear is the role of aerosol-cloud interactions (ACI). Satellite observations indicate that aerosols can invigorate convection in tropical deep convective clouds (Jiang et al., 2018). However, observations of ACI in TCs remain limited. In contrast, numerical simulations indicate that aerosol-induced convective invigoration can either weaken or strengthen TCs, depending on where the aerosols enter the storm (Lin et al., 2023; Hoarau et al., 2018).
In the future, aerosol concentrations are expected to decrease due to reductions in anthropogenic emissions (Riahi et al., 2017). The impact of this overall aerosol decline on TCs remains unclear. As part of the EU-funded CleanCloud project, our goal is to investigate TC dynamics in cleaner aerosol conditions to refine our understanding of ACI in TCs and improve future TC risk assessments.
We use the numerical weather prediction and climate model ICON (Zängl et al., 2015) in limited area mode using a 10 km horizontal resolution to run ensemble simulations of the North Atlantic TC season in 2020. Cloud processes are parameterized with a two-moment microphysics scheme (Seifert and Beheng, 2006) while deep convection parametrisation is disabled. Aerosols are uniformly prescribed in varying concentrations, allowing TCs to evolve in both clean and polluted conditions. By implementing a novel cyclone composite method that normalizes the storms by their eyewall location and extent, we evaluate the clean and polluted cyclone populations in terms of their circulation and structure. Our study compares TC activity on the storm scale in the 2020 TC season under both clean and polluted aerosol conditions, offering insights into how TC dynamics might be shaped by ACI.
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How to cite: Caratsch, A., Ferrachat, S., and Lohmann, U.: Tropical Cyclone Dynamics Shaped by Aerosol-Cloud-Interactions: A Composite Perspective Using ICON Ensemble Simulations., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5779, https://doi.org/10.5194/egusphere-egu25-5779, 2025.
Estimating the intensity of tropical cyclones has been a critical research topic in the field.
Theoretical models such as the potential intensity (PI), first introduced by Emanuel 1986 [1],
provide an upper bound for the intensity a tropical cyclone can achieve based on pre-storm
conditions. However, PI and other similar models are based on idealized settings that may
not always match real-world conditions, such as assuming a neutral atmosphere to moist
convection. Using simulations from the high resolution cloud resolving model SAM [3] in
rotating radiative-convective equilibrium settings, we assess the validity of the idealiza-
tions of the PI theory. We find that upper level processes are responsible for the intensity
oscillations of the tropical cyclone in the simulations, as confirmed by a recent study [5]. We
further show that when accounting for the upper level processes, it is possible to modify
PI such that it approximately follows the observed intensity evolution.
[1] K. A. Emanuel, J. Atmos. Sci. 43, 6 (1986).
[2] K. A. Emanuel et al., Annu. Rev. Earth Planet Sci. 31, 1 (2003).
[3] M. F. Khairoutdinov, D. A. Randall, J. Atmos. Sci. 60, 4 (2003).
[4] C. J. Muller, D. M. Romps, PNAS 115, 12 (2018).
[5] A. Polesello, G. A. Charinti, A. N. Meroni, C. J. Muller, C. Pasquero (submitted, 2025).
[6] A. A. Wing, K. A. Emanuel, J. Adv. Model. Earth Syst. 6, 1 (2014).
How to cite: Charinti, G. A., Polesello, A., Muller, C., Davin, A., and Pasquero, C.: Upper level processes in simple models for tropical cyclones in high resolution simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6646, https://doi.org/10.5194/egusphere-egu25-6646, 2025.
In early June 2023, New York City (NYC) and other cities in the northeastern US experienced a severe air pollution event. Although reports associated this hazardous pollution event with the smoke from Canadian wildfires, the factors triggering the southward waft of the smoke remain unclear. We found the northerly anomaly that transported the smoke was linked to the Rossby wave train excited by the Madden–Julian Oscillation (MJO) over the Philippine Sea, which led to the formation of an enhanced northerly at the western edge of the cyclonic anomaly over the East Coast–North Atlantic. When the MJO convection left the western Pacific, the disorganized teleconnection caused the pollution to dissipate. Observational findings were further supported by model simulations and predictions. These results suggest that monitoring and predictions of MJO activity may help mitigate air pollution events over the northeastern US during Canadian wildfire seasons.
How to cite: Zhu, Y., Hsu, P., and Qian, Y.: Influence of Western Pacific Madden–Julian Oscillation on New York City's Record‐Breaking Air Pollution in Early June 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6698, https://doi.org/10.5194/egusphere-egu25-6698, 2025.
This study undertakes a thorough analysis of the elements that influence the variability of tropical cyclones (TC) in the North Indian Ocean (NIO) from 1960 to 2020, with a specific focus on the periods before and after the monsoon season. The study utilizes historical satellite data to investigate the factors that impact the formation, strength, and trajectories of cyclones. The primary method for evaluating cyclone strength is by calculating the Accumulated Cyclone Energy (ACE). The study observes a decreasing trend in ACE levels during 1991–2005, which started increasing just after from 2006 to 2020. The Bay of Bengal (BoB) has a more uniform distribution of ACE in comparison to the Arabian Sea (AS), with higher average values and more variability over the Main Development Region (MDR), which is the area where cyclone development occurs most frequently. Cyclones of greater intensity generally occur following the monsoon season. Examination of storm paths reveals that cyclones with greater intensity frequently hit the northeastern and southeastern coastal regions of India. The study emphasizes notable discrepancies in parameters within the MDR, which impact cyclone strength and ACE values throughout various periods.
Keywords: ACE; Tropical Cyclone; Bay of Bengal; Variability
How to cite: Kumar Sagar, A. and Chakraborty, A.: Analyzing long term Spatial Changes of Parameters Affecting Cyclonic Activity over the North Indian Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7847, https://doi.org/10.5194/egusphere-egu25-7847, 2025.
According to the marsupial paradigm, some African Easterly Waves exhibit a pouch structure that shields convective systems from lateral intrusion of dry air. This protective mechanism also influences dust transport from the Saharan Air Layer, preventing its intrusion at mid to high altitudes. A Meso-NH model based simulation of the life cycle of Tropical Storm Rose (2021) is presented and validated against ECMWF ERA5 reanalyses as well as ground-based and airborne CADDIWA campaign data. The sensitivity of the model simulations to the concentration of dust is discussed. By modifying initial conditions, the impact of dust on the storm development and intensification is investigated with a specific focus on microphysics.
How to cite: Flamant, C., Jonville, T., Tulet, P., Feger, G., Chaboureau, J.-P., Gonthier, H., and Lavaysse, C.: Tropical Cyclogenesis Microphysics : modeling the impact of dust on Tropical Storm Rose (2021) development over the Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9984, https://doi.org/10.5194/egusphere-egu25-9984, 2025.
For many modelling applications, the total mass of the atmosphere and hence the global mean surface pressure can be considered constant and invariant under precipitation and evaporation. This is also the case for the atmosphere model ICON-A: Changes to the atmospheric water mass are compensated by changes in dry air composition, hence the mass of an atmospheric layer is constant and only its physical properties change. However, there are limits to this simplification, especially when it comes to modelling very moist environments or atmospheres. In moist environments, water becomes a major contributor to atmospheric mass and surface pressure, thus changes in water mass from evaporation and precipitation can affect the surface pressure.
By separating the atmospheric mass in ICON-A into contributions from dry air and from water constituents and by allowing the water component to vary with precipitation and evaporation, we are adding a simplified precipitation mass sink / evaporation mass source to the ICON-A model (for simplicity only referred to as ‘precipitation mass sink’).
The impact of this precipitation mass sink on atmospheric dynamics is investigated in a tropical cyclone test case: A vortex is initialised on a rotating aquaplanet and evolves into a tropical cyclone over the period of ten simulation days. Simulations with and without the precipitation mass sink are compared. The effect of the precipitation mass sink on cyclone development and, in particular, its strength are investigated.
How to cite: Tschirschwitz, J., Giorgetta, M., and Stevens, B.: The impact of changes of atmospheric water mass ontropical cyclone intensification in ICON-A, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10201, https://doi.org/10.5194/egusphere-egu25-10201, 2025.
A typhoon Hagupit (2020) that intensifies rapidly near the coast is simulated by using the Weather Research and Forecasting (WRF V4.2.1) model. The typhoon track, intensification, and precipitation simulated by WSM6, Morrison, and Goddard 4-ice cloud microphysics schemes were evaluated based on observations. The simulation biases during the typhoon’s Rapid intensification process were analyzed. The results showed that all three schemes effectively simulated the typhoon's track and precipitation, but their simulations of intensity varied significantly. The Morrison scheme better reproduced the typhoon's intensity, whereas WSM6 underestimated it and Goddard 4-ice overestimated it. Differences in the simulated typhoon intensity corresponded well with variations in the mass mixing ratio of ice-phase particles. During the intensification process, Goddard 4-ice exhibited the highest rate of ice particle formation through vapor deposition, while WSM6 had the lowest. Sensitivity experiments further demonstrated that latent heat release from the deposition of ice-phase particles warmed the air, which enhanced the typhoon's warm-core structure and strengthened the upward outflow in the eyewall. This process accelerated the inflow of low-level air toward the typhoon center, increasing the pressure gradient and maintaining the extremely low central pressure. This study proposes that the process of ice-phase hydrometeor deposition plays a critical role in simulating typhoon rapid intensification.
How to cite: Ye, G., Zhang, W., Leung, J. C.-H., Dong, W., and Zhang, B.: Comparison of Three Cloud Microphysical Schemes on the Rapid Intensification of Typhoon Hagupit (2020), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11740, https://doi.org/10.5194/egusphere-egu25-11740, 2025.
The Maritime Continent (MC) is the rainiest region on Earth, where extreme precipitation constitutes a major hazard. Convectively coupled Kelvin waves (CCKWs) are weather systems that travel eastwards across the equatorial waveguide and can trigger convection in their convergent phase. CCKWs are linked to up to a fourfold increase in precipitation rates across the equatorial Maritime Continent (Ferrett et al., 2020). However, not all CCKWs produce precipitation extremes. Recent studies reveal that CCKWs arriving in phase with the local diurnal cycle of convection may be more likely to cause high impact weather events or when part of a multiscale interaction with the MJO, organising the large-scale precipitation on a more localised scale (Baranowski et al., 2016; Baranowski et al., 2020; Latos et al., 2021; Senior et al., 2023).
Current methods for studying these mechanisms have some limitations. For example, composite studies of CCKWs are useful for revealing statistical links but smooth out key interactions. Case studies are useful for identifying mechanisms in particular high-impact weather events but are difficult to generalise. Modelling such high-impact weather events provides additional insights; however, lacks the capability for fine-tuning.
Hence, we have developed a methodology for introducing synthetic CCKWs into convection-permitting Met Office Unified Model (MetUM) forecasts. This involves generating 3D CCKW structures on key dynamical fields using ERA5 data and adding these to the model’s initial conditions. The methodology will be presented, and a comparison of diagnostics from control and perturbation experiments will be provided. We will then discuss how the methodology will be applied to studying the mechanisms through which CCKWs cause precipitation extremes across various locations in the MC. Since CCKWs are an important dynamical predictor of extreme precipitation, understanding these mechanisms is crucial for providing accurate forecasts of hazardous weather in the MC.
Baranowski, D.B. et al., (2016) Phase locking between atmospheric convectively coupled equatorial Kelvin waves and the diurnal cycle of precipitation over the Maritime Continent. Geophysical Research Letters, 43(15), 8269–8276. https://doi.org/10.1002/2016GL069602.
Baranowski, D.B. et al., (2020) Social-media and newspaper reports reveal large-scale meteorological drivers of floods on Sumatra. Nature Communications, 11, 2503. https://doi.org/10.1038/s41467-020-16171-2.
Ferrett, S. et al., (2020) Linking extreme precipitation in Southeast Asia to equatorial waves. Quarterly Journal of the Royal Meteorological Society, 146(727), 665–684. https://doi.org/10.1002/qj.3699.
Latos, B. et al., (2021) Equatorial waves triggering extreme rainfall and floods in Southwest Sulawesi, Indonesia. Monthly Weather Review, 149(5), 1381–1401. https://doi.org/10.1175/MWR-D-20-0262.1.
Senior, N.V. et al., (2023) Extreme precipitation at Padang, Sumatra triggered by convectively coupled Kelvin waves. Quarterly Journal of the Royal Meteorological Society, 149(755), 2281–2300. https://doi.org/10.1002/qj.4506
How to cite: Senior, N., Matthews, A., Webber, B., Sanchez, C., Jones, R., and Nurrahmat, M. H.: Introducing synthetic convectively coupled Kelvin waves into the Met Office Unified Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13846, https://doi.org/10.5194/egusphere-egu25-13846, 2025.
This study presents a 21-year climatology (1998–2018) of Easterly Wave Disturbances (EWDs) over the Tropical South Atlantic (TSA). The identification of these systems was performed subjectively using infrared satellite images and fields of relative vorticity and streamlines at 1000, 850, 700, 500, and 200 hPa levels from the ERA-Interim (ERAI) reanalysis. Additionally, the TracKH automatic tracking algorithm was applied, successfully capturing approximately 66% of the subjectively identified events. A total of 518 EWDs were recorded during the study period, with 97% reaching the Northeast Brazil (NEB) region, and 64% exhibiting convective characteristics. The highest frequency of events was observed between April and August, with an average of approximately 25 EWDs per year. The primary genesis areas were located between 20°S–5°N and 35°W–15°W. The trajectories and dissipation predominantly occurred along the NEB's eastern coastline, particularly between Alagoas and Rio Grande do Norte. Dissipation generally occurred rapidly after the systems moved inland. Several atmospheric systems were identified as key contributors to EWD genesis, including the Intertropical Convergence Zone (ITCZ), Upper-Tropospheric Cyclonic Vortices (UTCV), cold fronts, and convective clusters originating from the west coast of Africa. These factors played a significant role in the intensification and organization of the disturbances. During the wet season, the synoptic patterns associated with EWDs revealed anomalous cyclonic and confluent circulations, along with convergence and negative vorticity from low levels up to 200 hPa, where only a trough feature was observed. Negative anomalies of vertical motion and temperature, coupled with increased relative humidity, were also identified, fostering favorable conditions for enhanced convection and precipitation associated with the disturbances.
How to cite: Gomes, H., Hodges, K., Ray, P., Silva, M. C. L. D., Baltaci, H., Lyra, M. J. A., Herdies, D., Silva, F. D. D. S., and Gomes, H. B.: Easterly wave disturbances on tropical south Atlantic and their impact over northeast Brazil, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14182, https://doi.org/10.5194/egusphere-egu25-14182, 2025.
From 2000 to 2024, the Bay of Bengal has exhibited significant shifts in tropical cyclone behavior, reflecting the intricate interplay between oceanic and atmospheric processes in a warming climate. Cyclone intensity has surged markedly, with the frequency of super cyclonic storms (wind speeds >221 km/h) increasing by over 30% compared to the early 2000s. Despite a modest decline in overall cyclone frequency post-2015, a consistent rise in median wind speeds highlights the escalating severity of these events, underscoring an increased threat to coastal and marine ecosystems. Comprehensive analysis attributes these changes to a combination of rising sea surface temperatures (SSTs), frequently surpassing critical thresholds of 28°C to 31°C, and a progressive weakening of vertical wind shear in the region. Elevated SSTs have enhanced ocean-atmosphere heat and moisture fluxes, creating conditions conducive to rapid intensification (RI) events. These factors have not only increased the likelihood of more intense cyclones but also shortened the response time for disaster preparedness. Atmospheric shifts, including alterations in the Indian Ocean Dipole (IOD) phases and the Madden-Julian Oscillation (MJO), have further modulated cyclone genesis, track trajectories, and landfall patterns. Notably, a westward shift in cyclone landfall locations has increased the vulnerability of previously less-affected areas, necessitating the reassessment of risk management strategies. These atmospheric oscillations have also contributed to changes in the temporal clustering of cyclonic events, presenting new challenges for seasonal forecasting models. This study integrates satellite observations, reanalysis datasets, and advanced climate models to quantify the physical mechanisms driving these trends. By coupling high-resolution modeling with real-time atmospheric monitoring, the findings emphasize the need for predictive frameworks capable of capturing the complex dynamics of cyclone behavior. Such advancements are critical for enhancing early warning systems, informing regional climate adaptation policies, and mitigating the socio-economic and environmental impacts in one of the world's most cyclone-prone regions.
How to cite: Singh, A., Saini, A., and Jothiprakash, V.: Trends in Cyclone Intensity and Their Drivers in the Bay of Bengal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16482, https://doi.org/10.5194/egusphere-egu25-16482, 2025.
Over the summer of 2024, a wealth of experimental data was collected over the tropical Atlantic. First, the ORCESTRA campaign measured the ITCZ from the ground, sea, and air, offering a rich and detailed description of its complex structure. Coincidentally, the EarthCARE mission started releasing highly-resolved vertical profiles of deep convective systems. In parallel to these experimental studies, a numerical campaign was run almost in real time in the form of a limited-area model of the ITCZ. The model ran at 1.25 km resolution using the storm-resolving ICON-Sapphire configuration, in 48-hour-long bursts overlapping halfway through. This staggered approach was born of a compromise between 1) ensuring enough spinup time (first simulated day) and 2) keeping synoptic conditions close to ground observation for analysis (second simulated day). The resulting dataset allows us to compare the model with the aforementioned experimental missions, and assess its strength and weaknesses. Specifically, the model's capability in resolving the ITCZ structure and organisation of convection is scrutinized.
How to cite: Fiévet, R., Kornblueh, L., Linardakis, L., Hohenegger, C., and Stevens, B.: LAM-ORCESTRA: a Numerical Campaign over the Atlantic ITCZ , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16637, https://doi.org/10.5194/egusphere-egu25-16637, 2025.
Numerous studies focus on the impacts of ENSO diversity on tropical cyclone (TC) activities in the western North Pacific (WNP). In recent years, there is a growing threat of landfalling and northward-moving TCs in East Asia, accompanying an increase in central Pacific (CP) El Niño. Here, we aim to discover variations in landfalling TCs during various types of CP El Niño (CP-I and CP-II El Niño). It is found that significant changes in landfalling and going northward TCs over East Asia north 20N are modulated by CP-I El Niño. During CP-I El Niño, TCs tend to landfall more often over the mainland of China with longer duration, moving distance, and stronger power dissipation index (PDI) after land fall and increased TC-induced rainfall, due to favorable conditions (beneficial steering flow, weak vertical wind shear, increased specific humidity, increased soil moisture, and temperature), especially significant over the northeastern part. The situation over the mainland of China is reversed during eastern Pacific (EP) El Niño and CP-II El Niño, with a significant decrease in the characteristics with corresponding unfavorable environments. Over the Korean Peninsula and Japan, the frequency of TC landfalls, as well as the duration and the moving distance after landfall, exhibits greater levels during CP-I and CP-II El Niño than during EP El Niño due to favorable steering flow, and thus, TC-induced rainfall enhances correspondingly. Regarding the PDI over the Korean Peninsula and Japan, it remains relatively consistent across all El Niño types. However, a notable increase in the PDI during EP El Niño could be attributed to the higher intensity of TCs prior to landfall.
How to cite: Pan, L.: Distinct Features of Tropical Cyclone Landfall over East Asia during Various Types of El Nino, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17585, https://doi.org/10.5194/egusphere-egu25-17585, 2025.
Posters virtual: Tue, 29 Apr, 14:00–15:45 | vPoster spot 5
EGU25-2672 | ECS | Posters virtual | VPS2
Genesis, structure and propagation of synoptic systems over the Indian Ocean during the Northeast MonsoonTue, 29 Apr, 14:00–15:45 (CEST) vPoster spot 5 | vP5.28
The Northeast Monsoon (NEM) in South Asia, occurring from October to January, plays a pivotal role in precipitation, often giving rise to extreme weather events. This study aims to elucidate the diverse synoptic systems responsible for rainfall during the NEM and track their origins. Specifically, using a synoptic system tracking algorithm, we identify and characterise the genesis locations, propagation, and structures of these synoptic systems.
Our findings reveal a seasonally evolving latitude dependence in genesis locations, with a bimodal distribution that shifts southwards and becomes more meridionally confined as the season progresses. These genesis locations coincide with regions of high relative vorticity and column-integrated Moist Static Energy (MSE). Based on the pressure level at which maximum vorticity is observed at genesis, we classify these systems into three categories: Lower Tropospheric Cyclones (LTCs), Mid-Tropospheric Cyclones (MTCs), and Upper Tropospheric Cyclones (UTCs). Each category exhibits an evolving preference for genesis location, generally evolving southwards and eastwards, as the season advances. The UTCs are further categorised into two subtypes: one forming near the equator (up to 15°N/S) and another of subtropical origin (poleward of 15°N/S). Composites of near-equatorial UTCs display westward tilt with height, warm temperature anomalies at upper levels, and cold anomaly below, with vorticity maximum near 400 mb. This structure resembles that of MTCs, which exhibit a similar westward tilt and warm-over-cold core structure, but with maximum vorticity near 600 mb. In contrast, LTCs exhibit an upright structure with a warm core aloft and vorticity maximum centred around 800 mb. The joint distribution of MSE and relative vorticity at genesis indicates that LTCs are typically associated with stronger values of both variables, whereas UTCs and MTCs each appear in two distinct regimes: one with higher values of MSE and vorticity and another with lower values of these variables.
UTCs account for 14% of all systems, MTCs 44%, and LTCs 42%. Despite being fewer, on average a UTC produces rainfall of comparable magnitude to an MTC. UTCs predominantly generate precipitation over the Bay of Bengal shifting to the southwest Indian Ocean in January. MTCs generate significant rainfall over the Arabian Sea, Bay of Bengal, and South China Sea until December, and over Indo-Pacific region and the tropical South Indian Ocean in January. LTCs produce the largest rainfall, mainly over the Bay of Bengal and South China Sea, throughout the season and over the tropical South Indian Ocean as the season progresses. Lastly, while cyclonic propagation trajectories show overall westward movement for all categories, there are important differences: LTCs tend to have a more meridional motion towards northwest, while MTCs and UTCs exhibit a comparatively more zonally directed motion. Given the structural differences between systems, especially MTCs and LTCs, and their potential to morphologically evolve (e.g., MTC transitioning to LTC and vice versa), our study focussing on the genesis of these systems offer valuable insight into their formation mechanism.
How to cite: Jalan, S., Sukhatme, J., and Seshadri, A.: Genesis, structure and propagation of synoptic systems over the Indian Ocean during the Northeast Monsoon , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2672, https://doi.org/10.5194/egusphere-egu25-2672, 2025.
