OS1.2
Orals: Mon, 24 Apr | Room L2
EUREC4A-OA is a large international project, connecting experts of ocean and atmosphere observations and modelling to enhance the understanding of key ocean and air-sea processes at the and to improve the skill of forecasts and future projections.
The core of EUREC4A-OA has been a one-month (Jan/Feb 2020) field study in the western tropical North Atlantic Ocean where high-resolution, synchronized observational data have been collected using cutting-edge technology on ships, airplanes and autonomous vehicles. EUREC4A-OA investigates heat, momentum, water and CO2 transport within the ocean and exchanges across the air/sea interface using innovative high-resolution ocean observations and a hierarchy of numerical simulations. EUREC4A-OA focuses on ocean dynamics at the small-scale (0.1–100 km) and related atmospheric boundary layer processes. EUREC4A-OA is centered on the tropics where the primary external time scale affecting air-sea exchange is the diurnal cycle. However, the internal ocean and atmosphere dynamics convolute the diurnal, synoptic, seasonal and longer time scales to climate variability.
The talk will present some of the results we obtained so far from the observations collected during the field experiment and from numerical simulations. The analyses carried out revealed with unprecedented detail the particular characteristics of the ocean small-scale dynamics, enlightening that such scales are also very active in the tropical regions and not only over the mid and higher latitudes ocean. Observations and models also unveil that the ocean small scales is important in contributing to the exchanges of heat, freshwater and CO2 between the ocean and the atmosphere. Moreover, the evaluation of the intensity of the coupling between the ocean and the atmosphere assessed from data and high-resolution simulations show that they are very important and intimately linked with the 3D structure of the small-scale ocean dynamics. The project has also provided preliminary results in terms of parametrization of different processes influencing the ocean and atmosphere exchanges that have been uncovered by the EUREC4A-OA field experiment. Notably a better representation of the small-scale freshwater patches due to precipitation has been introduced in the French Earth-System model that improves the overall simulations of air-sea interactions and clouds. A similar parametrization is now been introduced to take into account these physical processes in air-sea fluxes of CO2.
How to cite: Speich, S., Karstensen, J., Reverdin, G., Olivier, L., Fernandez, P., L'Hégaret, P., Coadou, S., Laxenaire, R., Zhang, D., Gentemann, C., Landschutzer, P., Boutin, J., Bellenger, H., Pasquero, C., Meroni, A., Borgnino, M., Acquistapace, C., and Bopp, L.: Lessons learned from the EUREC4A-OA experiment on the impact of ocean small scales on air-sea interactions in the Northwest Tropical Atlantic, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3608, https://doi.org/10.5194/egusphere-egu23-3608, 2023.
Exchanges of momentum, energy and mass between the ocean and atmosphere are of large importance in regulating the climate system. Here we apply the Liang-Kleeman rate of information transfer to quantify interactions between the upper ocean and lower atmosphere over the period 1988-2017 at monthly time scale in two different case studies. In the first case study, we investigate dynamical dependencies between sea-surface temperature (SST), SST tendency and turbulent heat flux in satellite observations. We find a strong two-way influence between SST or SST tendency and turbulent heat flux in many regions of the world, with largest values in eastern tropical Pacific and Atlantic oceans, as well as in western boundary currents. The total number of regions with a significant influence of turbulent heat flux on SST and SST tendency is reduced when considering the three variables, suggesting an overall stronger ocean influence compared to the atmosphere. In the second case study, we focus on the influence of ocean heat transport convergence (dynamical influence) and net surface heat flux (thermodynamical influence) on upper ocean heat content tendency in three global climate models with at least two different ocean resolutions. We find that low-resolution model configurations (1° in the ocean) show a much larger number of regions with a significant dynamical influence compared to high-resolution model configurations. The reason for the large difference in dynamical influence between low and high resolutions partly comes from the spatial distribution of ocean velocity field, which displays a larger spatial variability at high resolution.
How to cite: Docquier, D., Vannitsem, S., Bellucci, A., and Frankignoul, C.: The rate of information transfer as a measure of ocean-atmosphere interactions, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4940, https://doi.org/10.5194/egusphere-egu23-4940, 2023.
The northern Indian Ocean serves as an ideal space to study the interaction between Ocean and atmosphere as it accommodates unique and versatile oceanic conditions and the largest monsoonal circulation in the world. The South Asian Monsoon System, the largest of its kind, directly impacts the lives and livelihoods of billions of people living in the Indian Subcontinent. Various factors that influence its strength and characteristics have been studied extensively throughout the years. But, owing to its complex and dynamic nature, a comprehensive understanding and accurate monsoon prediction remain a work in progress. Several Oceanic components that play a part in monsoon processes have been identified. Our study focuses on the Bay of Bengal, distinguished from other oceans due to its highly stratified upper layers. Through this study, we aim to understand the Impact of mesoscale eddies in the Bay of Bengal on the Indian Summer monsoon.
The influence of oceanic mesoscale eddies on the circulation and precipitation directly over them has been addressed through different studies after the advent of high-resolution satellite data. The current research focuses on the large-scale influence of the eddies in the Bay of Bengal on the seasonal rainfall during the Indian summer monsoon(ISM). Indices were created using the Okubo Weiss parameter to understand the inter-annual variation of eddies (classified according to polarities and regions of occurrence). These indices correlated with the ISM system suggested that Anticyclonic eddies in the Western Bay of Bengal strongly influenced wind and rainfall patterns over the monsoon region. The Anticyclonic Eddy activity that peaked during the El Nino years countered the suppression of rainfall by El Nino through enhanced synoptic activity in BoB. The low-pressure system formation and propagation in BoB were found to be stronger in the years having more anticyclonic eddies. The warming created by the warm-core Anticyclonic eddies initiates an Anticyclonic(Clockwise) circulation around the region, which feeds back into the existing oceanic conditions. This coupled Ocean-Atmospheric system mediated through the mesoscale eddies needs to be further analyzed through stand-alone and coupled modeling experiments. Improving the representation of the mesoscale processes in the Northern Indian Ocean can serve as a crucial step in improving the monsoon prediction systems.
How to cite: Vg, K., A Rao, S., and A Pillai, P.: Impact of Bay of Bengal mesoscale eddies on Indian Summer Monsoon Rainfall, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-514, https://doi.org/10.5194/egusphere-egu23-514, 2023.
The feedback of ocean surface currents to the atmosphere (CFB) has been shown to correct long-lasting biases in the representation of ocean dynamics by providing an unambiguous energy sink mechanism. However, CFB effects on the Gulf of Mexico oceanic circulation, mainly dominated by the Loop Current and large anticyclonic eddies that shed from it), remain unknown. Here, twin ocean-atmosphere eddy-rich coupled simulations, with and without CFB, are performed over 24 years (1993-2016) to assess to which extent CFB modulates the dynamics of the Gulf of Mexico. We show that CFB damps the mesoscale activity by roughly 20% over the Gulf of Mexico through the eddy killing mechanism and the associated transfer of momentum from mesoscale currents to the atmosphere, but also by modifying the production of eddy kinetic energy via barotropic and baroclinic instabilities. This energy adjustment results in increasing the mean Loop Current penetration into the Gulf of Mexico and plays a key role in determining the shedding of Loop Current Eddy and their subsequent preferential trajectories and properties.
How to cite: Larrañaga, M., Renault, L., and Jouanno, J.: Partial control of the Gulf of Mexico dynamics by the current feedback to the atmosphere, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-5161, https://doi.org/10.5194/egusphere-egu23-5161, 2023.
In recent years, studies have put forth various theories and findings on the role of oceanic equatorial Rossby waves (OERW) in the subseasonal-to-seasonal (S2S) predictability of the Indian Ocean (IO). While much of the scientific literature uses data from in-situ, satellite, and/or reanalysis datasets, this study focuses on reforecast fields from the European Centre for Medium-Range Weather Forecasting’s (ECMWF) S2S dataset. Evaluation of the model’s predictive skill in representing OERWs and the associated variations in sub-surface-to-surface interaction and air-sea coupling are discussed. This work provides a unique methodology to calculate and evaluate the predictability of OERWs from model forecast data, which, to the author’s knowledge, is the first of its kind to do so. Our results indicate that the model forecasts OERWs with relatively high skill (anomaly correlation > 0.5 out to 40 days), indicating they are a key source of oceanic subseasonal predictability at extended lead times. Analysis of the wavenumber-frequency spectra for the IO indicates a reduction in power throughout the model forecast time period in the oceanic equatorial Kelvin wave (OEKW) regime, indicating the potential misrepresentation of the zonal winds. This erroneous weakening of the OEKWs are attributed to the weakening of the reflected oceanic equatorial Rossby waves (OERWs). This results in weaker transport of the associated westward advection of warm ocean heat content (OHC) anomalies via the OERWs, which has numerous implications for air-sea and sub-surface-to-surface coupling as will be discussed. In general, the atmospheric response to the waning westward transport of OHC anomalies in the western IO is associated with the weakening of precipitation anomalies related to the diminishing intraseasonal oscillation.
How to cite: Christophersen, J., Rydbeck, A., Flatau, M., Janiga, M., Reynolds, C., Jensen, T., and Smith, T.: Oceanic Rossby Wave Predictability in ECMWF’s Subseasonal-to-Seasonal Reforecasts, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1334, https://doi.org/10.5194/egusphere-egu23-1334, 2023.
The so-called frontal-scale air-sea interaction describing the atmospheric responses to oceanic fronts has been mainly discussed in the context of interactions between sea surface temperature and surface winds. The ocean current also influences the surface winds, which can significantly affect the atmosphere, especially in regions of energetic ocean currents and mesoscale activities as in the western boundary current systems. This study uses an atmosphere-ocean coupled model to analyze how the Kuroshio Current affects the momentum and turbulent heat fluxes and the atmospheric boundary layer and how these responses feed back to the ocean and atmosphere in this region. The ocean current coupling influences the path of Kuroshio extension and the eddy activities by mechanical and thermal current feedbacks. Mechanical current feedback reduces momentum flux and damps eddy kinetic energy (EKE) by reducing wind work as expected. On the other hand, the thermal current feedback associated with turbulent heat fluxes injects EKE by baroclinic energy conversion. Overall, the shift of Kuroshio Current and the change of eddy activities impact the region of strong turbulent heat release to the atmosphere, which can eventually trigger changes in weather systems.
How to cite: Cho, A., Song, H., and Seo, H.: Atmospheric and Oceanic Responses to Surface Current Coupling near the Kuroshio Current, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11795, https://doi.org/10.5194/egusphere-egu23-11795, 2023.
Coral bleaching events are more frequent and severe as global temperatures rise and marine heat waves are more frequent. However, quantifying the surface energy fluxes in coral reefs at various geoclimatic regions and the mechanisms by which the air-water interactions regulate water temperature is rare. We measure surface energy fluxes over coral reefs using Eddy Covariance towers in two contrasting geo-climatic regions: The typical setup of humid/tropical coral reefs (Heron Reef, Great Barrier Reef, Australia) and the rarer desert coral reef (Golf of Eilat, Israel). We analyze how the surface heat fluxes regulate the temperature of shallow coral reef environments. We show that in the desert reefs, the dry air overlying the shallow coral reef results in extremely high evaporation rates which in turn results in extensive cooling of the water. In humid/tropical reefs, evaporation is suppressed by humidity and is limited in the ability to offset the heating of the water. The extreme difference in evaporative cooling in desert versus tropical reefs is key in the response to marine heat waves. Marine heat waves which impose thermal stress on corals are a result of synoptic-scale circulation variations which suppress evaporation and increase heating. The most severe marine heatwave ever measured at the Gulf of Eilat (August 2021) was found to be caused by low evaporation rates, which resulted from synoptic circulation with weak winds and high humidity. After the onset of water temperature rise and the return of the dry winds, evaporation instantly cooled the water overlying the corals- relieving potential stress. Whereas, at the humid/tropical Heron Reef (Great Barrier Reef, Australia) evaporation solely is unable to reduce the high water temperature and therefore coral heat induce stress events are inevitably longer and more frequent. We conclude that evaporative cooling is a key mechanism protecting coral reefs located in deserts from extreme high-water temperatures, thereby representing possible thermal refugium for corals against background global warming.
How to cite: Abir, S., McGowan, H. A., Shaked, Y., and Lensky, N.: Identifying an Evaporative Thermal Refugium for the Preservation of Coral Reefs in a Warming World—The Gulf of Eilat (Aqaba), EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16883, https://doi.org/10.5194/egusphere-egu23-16883, 2023.
Hitherto unresolved oceanic sub-mesoscale variability may retard air-sea exchange of heat and carbon in contemporary IPCC-type model projections. Here, we set out to put this hypothesis to the test in the Atlantic in a region off Mauretania that is renown for its complex coastal dynamics. Results from a suite of coupled ocean-circulation biogeochemical models suggest that the oceanic bottleneck between the atmosphere and the vast abyssal stocks of heat and carbon is relatively insensitive in the range from mesoscale and to sub-mesoscale resolution. More specifically we find that the sensitivity of effective vertical mixing to changes in spatial resolution is comparable to infamous uncertainties associated with contemporary numerical algorithms.
How to cite: Dietze, H., Löptien, U., Hordoir, R., and Renz, M.: Beyond Mesoscale off Mauretania, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8293, https://doi.org/10.5194/egusphere-egu23-8293, 2023.
The accuracy of weather and climate models depends on reliable quantification of air-sea momentum transfer. While decades of research has led to significant improvements to momentum flux parameterization, even the most robust models are developed from open-ocean measurements where conditions are spatially uniform and similarity theory generally applies. Nearshore, wave shoaling and breaking, varying wind-swell incidence angles, complex currents patterns, rapid bathymetric changes, and shore-side topographic features all contrast open-ocean homogeneity meaning flux parameterizations are less effective. Therefore, there is a critical need to identify and systematically quantify the impact of coastal processes and features on the momentum flux. To this end, we deployed a suite of sonic anemometers outside the surfzone and onshore at the Army Corp Field Research Facility (FRF) in Duck, North Carolina, USA. Complimented by FRF’s extensive metocean observational network, we used our data to study the horizontal and vertical momentum flux variability with to understanding how transient nearshore processes and flux footprints alter the flux. This presentation will focus on the surfzone momentum flux as observed during a strong storm and compare it to the flux collect further offshore.
How to cite: Potter, H.: Direct Observations of the Momentum Flux in the Surfzone, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-17014, https://doi.org/10.5194/egusphere-egu23-17014, 2023.
In the past decades, numerous studies have shown that oceanic mesoscale activity, over scales of O(50–250) km, has a strong influence on the atmosphere through both the Thermal FeedBack (TFB) and the Current FeedBack (CFB). However, at the submesoscale, over scales of O(1–10) km, both TFB and CFB are not well understood, mainly due to technical barriers (observation and simulation). Here, a realistic high-resolution coupled oceanic model (dx = 1 km), including tidal forcing and river discharge, and atmospheric (dx = 2 km) model in the lower North Atlantic trades region over a period of 1-year (from July 2019 to June 2020) is used to assess the atmospheric response to submesoscale processes. We used classic coupling coefficients between the ocean and the atmosphere to quantify spatial and temporal variabilities of the TFB and CFB coupling.
Our results show that, similar to oceanic mesoscale activity, at the submesoscale, both TFB and CFB have an imprint on the low-level wind, surface stress and turbulent heat fluxes. On the one hand, the linear relationship between surface wind (stress) curl and surface current vorticity existing at the mesoscale regime is also supported at the submesoscale. At submesoscale, CFB, as at the mesoscale, is acting as a sink of energy from the ocean to the atmosphere, acting as an submesoscale eddy killer. Furthermore, the magnitude of surface stress curl introduced by submesoscale processes is greater by ~17 % than that presented by mesoscale processes, which is explained by a reduction of the wind response by ~55 %. On the other hand, the linear relationship between wind stress magnitude, or latent heat flux, and sea surface temperature (SST) anomalies, widely present at the mesoscale, is also found at the submesoscale. Similar results are found when considering wind stress curl/divergence and crosswind/downwind SST gradients coupling coefficients. However, the magnitude of the corresponding TFB coupling at submesoscale is reduced by ~30 % with respect to those at mesoscale.
Overall, our results emphasize the significant impact of both oceanic currents and strong SST fronts on the local wind/stress and latent heat flux response at the submesoscale regime.
How to cite: Conejero, C., Renault, L., and Giordani, H.: Mesoscale and Submesoscale air-sea interactions in the lower North Atlantic trades, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13039, https://doi.org/10.5194/egusphere-egu23-13039, 2023.
Full understanding of air-sea interaction requires observations not only at the air-sea interface but also through the entire air-sea transition zone (the upper ocean, air-sea interface, and marine atmospheric boundary layer as a single identity). Our capabilities of observing collocated and simultaneous profiles through the entire column of the air-sea transition zone are currently limited. This study explores the feasibility of using combined uncrewed robotic systems in conjunction with conventional platforms to provide such collocated and simultaneous profiles of the air-sea transition zone. An introduction is given to experimental deployments of uncrewed surface vehicles (saildrones), underwater vehicles (gliders), aerial vehicles in coordination with profiling floats, surface drifters, airborne dropsondes, and moored buoys to observe the air-sea transition zone. Based on the preliminary results and lessons learned, a vision of potential capabilities of observing the air-sea transition zone in the future using combined uncrewed systems is offered.
How to cite: Zhang, C. and the Saildrone Hurricane Observations Mission Team: Observing the Air-Sea Transition Zone using Combined Uncrewed Systems and Other Conventional Platforms, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-8166, https://doi.org/10.5194/egusphere-egu23-8166, 2023.
Extreme surface turbulent heat fluxes affecting convective processes in subpolar ocean regions may amount to 1000-3000 W/m2. Their quantitative estimation is critically important for many oceanographic and meteorological applications. Extreme turbulent fluxes are largely responsible for the vertical mixing in the ocean, especially in the subpolar latitudes where deep convection forms intermediate waters. Over western boundary currents and their extension regions very strong turbulent heat fluxes may result in local responses in the lower atmosphere on time scales from several hours to days and spatial scales from several kilometers to several tens of kilometers. Accurate estimation of extreme turbulent fluxes also strongly relates to the sampling problem especially for the poorly and irregularly sampled regions. Estimation of extreme turbulent fluxes is thus requires knowledge of probability distribution of fluxes. We suggest a concept for determination of extreme surface turbulent heat fluxes based upon theoretical probability distributions, which allow for accurate estimation of extreme fluxes. In this concept the absolute extremeness of surface turbulent fluxes is quantified from the Modified Fisher-Tippett (MFT) distribution. Further we extend MFT distribution to a fractional distribution, quantifying the so-called relative extremeness, representing the fraction of surface flux accumulated during continuous time (e.g. months, season) due to most intense surface fluxes (e.g. the strongest 1% of flux events). We provide explicit form of the fractional distribution and effective algorithms for parameter estimation.
Further we demonstrate applications of the concept for the global ocean using reanalyses and Voluntary Observing Ship (VOS) data for the period 1979 onwards. Global climatologies reveal that the regions with the strongest relative extremeness are not collocated with the strongest mean fluxes. Moreover, interannual variability of the absolute and relative flux extremes is not necessarily correlated with variability of mean fluxes. Growing mean flux may result in both increase and decrease of absolute and relative extremes that has implications for estimates of linear trends which may have different signs for mean fluxes, absolute and relative flux extremes – the situations found for the western boundary currents and major convections sites. Suggested concept has also profound implications for comparative assessments of surface turbulent fluxes from reanalyses (ERA5, ERA-Interim, CFSR, MERRA2, NCEP-DOE, JRA55) and satellite (IFREMER, J-OFURO, HOAPS, SEAFLUX) products. High mean fluxes in some products are not necessarily associated with the strongest absolute and relative extremeness in the same products and vice versa. Also a new concept allows for accurate estimation and minimization of sampling biases in VOS and satellite flux products. Finally, we analyzed the mechanisms responsible for forming extreme surface turbulent fluxes associated with cold air outbreaks in the rear parts of midlatitudinal cyclones under locally high winds and strong air-sea temperature gradients.
How to cite: Gulev, S., Belyaev, K., and Tilinina, N.: Extreme air-sea turbulent heat fluxes over the global oceans: determination, implications and mechanisms, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2957, https://doi.org/10.5194/egusphere-egu23-2957, 2023.
Ocean heat stored in the Western Pacific Warm Pool (WPWP) helps drive some of the foremost modes of weather and climate variability including ENSO, Intraseasonal Oscillations, and tropical cyclones. To understand the associated coupled mechanisms that regulate ocean temperature, we use reanalysis and a novel moored microstructure dataset yielding estimates of the turbulent ocean heat flux (Jq(z)) to describe how WPWP mixing is regulated by seasonal, intraseasonal, and synoptic-scale atmospheric disturbances. It is argued that observed variations in Jq(z) impact seasonal-to-synoptic trends in SST and mixed-layer depth. Jq(z) is weakest during Spring (dry season), when heat fluxes into the ocean (Qnet > 0) create a shallow mixed layer (ML) of warm water that lays undisturbed atop the seasonal thermocline. In the Summer, westerly winds associated with the Asian Monsoon create favorable conditions for tropical depression-like (TD-like) storms, which in turn cause episodic spikes in Jq(z) that gradually deepen the ML and momentarily cool sea surface temperature (SST) while the background SST continues to rise. Towards the end of the summer, SST at our mooring was greater than 30.7 °C but rapidly dropped and stabilized below 29.5 °C after a strong pulse of the Madden-Julian Oscillation (MJO) cooled the upper ocean and deepened the ML for almost 15 days in a row. Enhanced upper ocean mixing continued to be episodic throughout the Fall as TD-like storms and intraseasonal disturbances moved over the mooring site. Mixing remained high throughout the Winter, when cold outbreaks forced the upper ocean at high frequencies and mean convective cooling (Qnet < 0) further contributed to mixing. A similar seasonality is observed at the thermocline level, where Jq(z) is enhanced by storm-driven near-inertial internal waves (NIWs) whose power peaks between Fall and Winter. While intraseasonal wind bursts had the greatest impact on near-surface mixing, synoptic disturbances generated greater-amplitude NIWs and thus had a greater potential to mix temperature gradients in the permanent thermocline. Lastly, we use reanalysis data to argue that storm-driven mixing shapes interannual relations between SST, storm activity, and the Asian Monsoon.
How to cite: Gutierrez Brizuela, N., Xia, Y., Xie, S.-P., Alford, M., and Moum, J.: Seasonal buildup and downward transfer of Warm Pool heat content by wind-driven ocean mixing, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3693, https://doi.org/10.5194/egusphere-egu23-3693, 2023.
How to cite: Putrasahan, D. and von Storch, J.-S.: Geographical distribution and spatio-temporal scale dependence of air-sea coupling via the vertical mixing mechanism, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4685, https://doi.org/10.5194/egusphere-egu23-4685, 2023.
Tropical cyclones (TCs) are severe weather marvels, occur in warm tropical waters. These phenomena are among the most influential atmospheric-oceanic events in subtropics regions as the northern part of the Indian Ocean, affecting the Arabian Sea and the Oman Sea, which often cause severe damage to the coastal areas. The interaction between the atmosphere and the upper ocean plays an important role in the structure of TCs, in which successful connections between ocean circulations and the intensity and track of TCs have been identified. TCs derive their energy primarily from the release of latent heat through evaporation and sea spraying in the atmosphere boundary layer. This implies that the presence of a moisture source, with sufficiently warm sea surface temperature (frequently above 26°C) is required to sustain the flux of moisture from the ocean to the atmosphere. The most visible effect of TC passage is the cooling of the sea surface temperature (SST) as the response of the ocean mixed layer (OML) temperature. This decrease in SST has a negative feedback on the intensity of TCs, as it suppresses the heat exchange flux between the atmosphere and the ocean, consequently it can affect the TC track.
To investigate the effect of the temperature field on TCs structure, TC Shaheen (2021) with unusual track and entry into the Gulf of Oman is studied. In this regard, Weather Research and Forecasting (WRF) model was used with two different configurations. First, WRF was ran standalone and SST field was only adopted from global models as initial conditions and were not updated during the simulation. Then, as the second configuration, WRF model was coupled with an ocean finite volume model and the SST field was updated online during the simulation. The initial conditions of the ocean temperature, salinity and velocity field were taken from GOFS 3.1 global reanalysis product from the HYCOM Consortium. Primary result for the selected event implies that SST correction during TC simulation with WRF improves air-sea heat flux and has a pronounced effect on the TCs’ intensity and track predictions. Cold wake underside of the TC led to a remarkable heat flux loss from ocean surface into the storm. Hence, the TC size is reduced and the maximum wind speed of the storm is intensified.
How to cite: Farhangmehr, A., Ghader, S., Ali Akbar Bidokhti, A. A., and Ranji, Z.: A Preliminary Forecast Study of the North Indian Ocean Tropical Cyclones Using a Coupled Atmosphere-Ocean Model, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7362, https://doi.org/10.5194/egusphere-egu23-7362, 2023.
A new ocean-atmosphere-wave regional coupled model named Windwave version 1.0 for simulating and predicting winds and waves has been developed for the Northwest Pacific Ocean. In particular, the global-to-regional nesting technique is adopted for the ocean component to alleviate the bias due to the inconsistency in the lateral boundary. This paper is devoted to describing the coupling details of Windwave and the initialization scheme and assessing its basic performance, especially in predicting surface winds and significant wave heights (SWH) on the weather timescale. The control experiment set contains 31 experiments for August 2020, with seven typhoons passing through the Northwest Pacific. Each experiment starts at 0:00 am UTC of each day and runs for three days. Experiment results show that the new coupled model performs well in predicting surface winds, SWH, surface air temperature, and sea surface temperature on the weather timescale. In particular, the Root Mean Square Errors (RMSEs) of surface winds at 10 m height over the Northwest Pacific of the control experiment are 1.82 m s-1, 2.22 m s-1, and 2.59 m s-1, respectively, at lead times of 24 h, 48 h, and 72 h. Meanwhile, the RMSEs of SWH at lead times of 24 h, 48 h, and 72 h are 0.39 m, 0.43 m, and 0.51 m. In addition, we have explored the impacts of the different sea surface aerodynamic roughness parameterization schemes on predicting surface winds and SWH. In total, five different sea surface aerodynamic roughness parameterization schemes are adopted, corresponding to one control set and four sensitivity sets of experiments. Under normal conditions, the sea surface aerodynamic roughness parameterization scheme considering the effects of wind-wave direction tends to perform better for winds and waves, while that depending on wave age and SWH tends to perform worse. Under extreme wind and wave conditions, the schemes considering the effects of wind-wave direction and that considering wave age and peak wave length have better performance. These findings can provide new insights for developing a more advanced sea surface aerodynamic roughness parameterization scheme.
How to cite: Fu, S., Huang, W., Lv, R., Yang, Z., Qiu, T., Sun, D., Luo, J., Huang, X., Fu, H., Luo, Y., and Wang, B.: Develop an ocean-atmosphere-wave regional coupled model Windwave version 1.0 for predicting wind and wave conditions of the Northwest Pacific Ocean, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3127, https://doi.org/10.5194/egusphere-egu23-3127, 2023.
Posters on site: Mon, 24 Apr, 10:45–12:30 | Hall X5
In autumn and winter, the dynamics and thermodynamics of the anticyclonic eddies detached from the Loop Current in the Gulf of Mexico are strongly influenced by the passage of cold fronts and Northerly winds. In turn, the interaction between the wind and these anticyclonic eddies modulates vertical nutrient fluxes, biomass, and phytoplankton community distribution at mesoscale and sub-mesoscale. In this work, the physical mechanisms of eddy-cold front interactions are analysed based on high-resolution (3 km) numerical simulations of the NEMO (Nucleous for European Modeling of the Ocean) model, contrasting simulations that partially include or not the effect of ocean currents on the wind stress (the so-called current feedback). This analysis is part of a work in progress focused on developing and implementing a high-resolution ocean-atmosphere coupled model for the Gulf of Mexico.
How to cite: García Martínez, I. and Sheinbaum Pardo, J.: Current feedback in an anticyclonic eddy during the passage of cold frontal systems over the Gulf of Mexico, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-314, https://doi.org/10.5194/egusphere-egu23-314, 2023.
A cross-equatorial low-level wind, known as Findlater Jet (FJ), modulates the thermocline in the Arabian Sea (AS) during the summer monsoon (June to September). By analyzing ocean and atmospheric data, we show that the FJ signal gets ‘trapped’ in the AS in the form of tropical cyclone heat potential till the following winter monsoon months (December to February). This memory is the consequence of the combined effect of FJ-induced wind stress curl and the annual downwelling Rossby waves in the AS. During the summer monsoon months, the strong low-level westerly winds cause a negative wind stress curl in the south of the FJ axis over the central AS, resulting in a deep thermocline and a high magnitude of heat being trapped. In winter monsoon months, though the wind stress curl is positive over large parts of the AS and could potentially shoal the thermocline and reduce the tropical cyclone heat potential in the central AS, this does not happen due to two reasons. Firstly, winds are weaker and spread over a larger area over the AS making the magnitude of the wind stress curl low. Secondly, the westward propagating downwelling Rossby wave radiated from the eastern AS deepens the thermocline and prevents ventilation of the trapped heat. During the following spring, the collapse of the Rossby waves leads to the shoaling and mixing of underlying waters with surface waters thereby resurfacing the trapped heat. The resurfacing of the trapped heat makes the AS a memory bank of the FJ-induced signal.
How to cite: Kushwaha, V. K., Kumar, P., Francis, F., and Karumuri, A.: Findlater jet induced summer monsoon memory in the Arabian Sea, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-522, https://doi.org/10.5194/egusphere-egu23-522, 2023.
The Bay of Bengal is a unique tropical ocean basin because of seasonally reversing monsoon
winds; copious freshwater discharge from nearby continental rivers helps barrier layer formation.
Again, due to its capacity to keep warm SST beyond 28oC, the bay is prone to tropical cyclones
during the transition between two monsoons. Geographically, the basin is land bounded on three
sides and connected to global oceans through its southern boundary. Vicinity to the equatorial
The Indian Ocean facilitates the propagation of Kelvin waves through its rim as coastally trapped
waves. Hence, local and remote forcings make the bay an active basin for brewing mesoscale
features like eddies. Eddies play a vital role in the bay's upper ocean mesoscale dynamics (O[100s
Km]). Surface intensified eddies are well studied, but very little is known about subsurface
circulations. Limited literature reports active subsurface eddy fields in the basin. Observations by
a RAMA buoy at 90oE, 15oN from 2007 to 2020 shows a thermocline bulge. For about a month,
this peculiar subsurface feature is characterized by the doming (denting) of the seasonal
thermocline's upper (lower) part. The bulge is a regular seasonal feature during the winter
monsoon as denoted by time series analysis of D26 (depth of 26oC isotherm) – D12 (depth of
26oC isotherm) from RAMA temperature. This research, using a suite of in-situ moored buoy
observations, satellite altimetry, OSCAR surface current, near-surface ASCAT wind and HYCOM
re-analysis data, suggests a possible mechanism for the formation of thermocline bulge. Usually,
it isn't easy to detect a subsurface feature from the sea surface variables like SST or SLA. But
eddy-wind interactions can lead to the local generation of lens-shaped features in the
thermocline of a pre-existing surface-intensified anti-cyclonic eddy. Observations show the
simultaneous development of a surface anti-cyclone off the Irrawaddy delta (hereafter referred
to as ICAE) and upwelling-favourable winter monsoon winds in the background. The interaction
of background wind stress with the IACE facilitates the formation of a bulge by doming the
seasonal thermocline at the eddy core. The thermocline bulge starts its westward journey along
with the parent eddy due to Rossby wave forcing in December and crosses the RAMA buoy in
mid-January. Three factors are responsible for a bulged IACE off the Myanmar coast: 1. the arrival
of coastal Kelvin waves due to intense remote equatorial forcing by Wrytki jets, 2. eddy
separation from the coast, and 3. Ekman suction (or upwelling) at the centre of IACE due to local
"eddy-wind" interaction during late fall to winter. The IACE that wraps a bulged thermocline in
its core is an example of seasonal mode-water ACE or intra-thermocline eddy during the winter,
typical in higher latitudes but only recently observed in tropical basins like the Bay of Bengal.
How to cite: Kalita, B. K. and Vinayachandran, P.: Role of coastally trapped waves of remote origin and local eddy-wind interaction in the formation of seasonal thermocline bulge in the Bay of Bengal , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-713, https://doi.org/10.5194/egusphere-egu23-713, 2023.
How to cite: Flora, S., Ursella, L., and Wirth, A.: Superstatistical analysis of sea surface currents in the Gulf of Trieste, measured by HF Radar, and its relation to wind regimes, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1063, https://doi.org/10.5194/egusphere-egu23-1063, 2023.
We evaluated the ¼° model NorESM1.3 in which the well-known “double-ITCZ problem” in the Pacific is mitigated. However, excessive precipitation is produced in the northern branch of the ITCZ. The excessive precipitation is consistent with overevaluated latent heat flux in the tropical ocean. Further analysis shows that in NorESM1.3, the latent heat flux is too sensitive to the surface wind. The increased sensitivity in the ¼° model is partly contributed by small-scale air-sea interaction. The sensitivity of latent heat flux to surface wind, with the scale finer than 2.5°, is up to 40 (Wm-2 / ms-1), which is almost twice of that with scale coarser than 2.5°. This study helps to understand extra air-sea interaction resolved by higher-resolution models, and helps to tune and correct the related model bias.
How to cite: Tian, F., Keenlyside, N., Bethke, I., Koseki, S., and Li, F.: Resolution sensitivity of tropical turbulent fluxes and precipitation in NorESM models, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1996, https://doi.org/10.5194/egusphere-egu23-1996, 2023.
The phenomenon of sea surface temperature (SST) anomalies created by oceanic diurnal warm layers has been extensively studied for the last decades, but the assessment of its importance for atmospheric convection has come within reach only very recently, thanks to the development of kilometre-scale simulations. We use the output of a global coupled simulation with a 5km horizontal grid spacing and near-surface ocean layers of order O(0.5m) to explicitly resolve both atmospheric convection and diurnal warm layers. As expected, the simulations produce daily SST fluctuations of up to several degrees. The increase of SST during the day causes an abrupt afternoon increase of atmospheric moisture due to enhanced latent heat flux. This increase is followed by an increase in cloud cover and cloud liquid water content. However, although the daily SST amplitude is exaggerated in comparison to reanalysis, the impact on cloud cover and cloud liquid water content only lasts for 5-6 hours. Moreover, the global daily average of these quantities is not influenced by their increase. All in all, we conclude that the global short-timescale impact of diurnal warm layers is negligible.
How to cite: Shevchenko, R., Hohenegger, C., and Schmitt, M.: Impact of Diurnal Warm Layers on Atmospheric Convection, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2108, https://doi.org/10.5194/egusphere-egu23-2108, 2023.
The Ieodo Ocean Research Station (Ieodo ORS) is a fixed marine observation platform at the boundary of the Yellow and East China Seas. In 2019, a Category 4 Typhoon Lingling passed by the Ieodo ORS very closely. At that time, the Ieodo ORS observed Sea Surface Temperature (SST) cooling of 4.5°C by vertical mixing and negative turbulent heat flux (i.e., the sum of sensible and latent heat fluxes) due to the SST cooling. In this study, uncoupled and coupled simulations were conducted to examine the role of air-sea interactions in changes in atmospheric frontogenesis around the typhoon passage. In the coupled simulation, SST cooling up to 6°C occurred over the dangerous semicircle due to vertical mixing induced by wind stress. Strong wind stress also enhanced the SST gradient and, therefore, contributed to the formation of a steeper atmospheric frontal zone. Moreover, the comparison with reliable datasets supports the physical linkage between SST cooling and atmospheric frontogenesis by utilizing the meridional theta-e gradient and moisture convergence zone. Therefore, we hope to improve our understanding of atmospheric frontogenesis by air-sea coupling processes in developing a coupled atmosphere-ocean modeling system from the simulation results.
How to cite: Yang, S., Moon, I.-J., Bae, H.-J., Kim, B.-M., Byun, D.-S., and Lee, H.-Y.: Intense atmospheric frontogenesis by air-sea interaction captured at Ieodo Ocean Research Station during Typhoon Lingling (2019), EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4800, https://doi.org/10.5194/egusphere-egu23-4800, 2023.
It is known that oceanic conditions can play a crucial role in the intensification of tropical cyclones (TCs) when atmospheric conditions are conducive. However, the relative roles of ocean temperature and salinity stratification on ocean mixing and TC-induced sea surface temperature (SST) cooling are unclear. Temperature stratification has competing effects on cooling from ocean mixing: stronger stratification leads to cooler water near the surface which can enhance SST cooling (thermodynamic effect), yet it also leads to resistance to vertical mixing due to a stronger density gradient and increased static stability (mixing effect). In contrast, salinity stratification almost always acts to reduce mixing and cooling. To investigate the mechanisms that control the amount of ocean cooling under a storm, we use a one-dimensional mixed layer model, initialized with different oceanic profiles and forced with cyclones of various intensities, translation speeds, and sizes. We then compare output from the mixed layer model with observations. Results consistently show that the thermodynamic effect (changes in vertical temperature gradient with density gradient held constant) is 2-3 times that of the mixing effect (changes in density stratification with temperature stratification held constant). Furthermore, we find that translation speed and storm size are the two most important factors for SST cooling, followed by temperature stratification, maximum wind speed, and mixed layer depth, respectively. These results emphasize the importance of temperature stratification over most of the tropical cyclone basins and the often overlooked role of storm size.
How to cite: Looney, L. and Foltz, G.: The Competing Forces of Hurricane-Induced Ocean Cooling, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10356, https://doi.org/10.5194/egusphere-egu23-10356, 2023.
The study of marine aerosols size distribution and cloud condensation nuclei (CCN) properties is of major interest as they influence clouds life and clouds radiative properties, particularly in the remote ocean which remains poorly documented. Several short campaigns focusing on specific regions as phytoplankton bloom regions, pristine regions or remote areas influenced by continental air masses took place to address this issue. However, long sampling periods targeting different in-situ conditions had not been realized.
In this context, the MAP-IO program was launched with the aim of providing a large new set of marine aerosol observations (size distribution from 10 nm to 10 µm and CCN properties) on different sea state and meteorological conditions. Thus, the Marion Dufresne vessel has been equipped with a set of various instruments described in Tulet et al. (in preparation) or on the website www.mapio.re. Two years after the launch of the program, we now have aerosol observations (about 200 days) over an area covering 50 ° of latitudes and extending from the Tropics to the upper Southern Ocean.
These measurements were first used to investigate the size distribution and CCN variability of marine aerosols according to local conditions (sea states and wind speed).The results highlight that at the lowest latitudes (south of 50 °S) the minimum concentration of CCN tends to increase when the wind speed exceeds approximately 12 m s-1, which is consistent with the literature as sea salt emissions are mechanically driven by local conditions and tend to be predominant from 10 m s-1. .When analyzing the size distributions of aerosols according to the wind speed during a 5-day storm that occurred in the Southern Ocean, we found that: (1) the number of particles with a diameter less than 500 nm is predominant and stable over the full range of wind speeds (4 to 33 m s-1), (2) the number of aerosols with diameter greater than 500 nm remains low under 10 m s-1 and increases from 10 m s-1 to 33 m s-1 to finally reach the concentration of the particles with diameter less than 500 nm at 33 m s-1.
Taking this first analysis into account, further work will focus on average size distributions per region, season, origin of air masses (from simulated FLEXPART back trajectories) and wind speed conditions. Analysis of these distributions is unique due to the size of the database, the variability of regions encountered and knowing that the measurements were carried out with the same experimental device.
Finally, to deepen the study, the activation diameter of marine aerosols will be determined and the hygroscopicity parameter Kappa-Köhler will be calculated (Petters and Kreidenweis, 2007) in this case to distinguish sea salts (Kappa~1.2) from organic matter (0.01<Kappa<0.5).
How to cite: Meredith, D., Pierre, T., Joris, P., Karine, S., and Jérôme, B.: Overview of aerosol observations from the Marion Dufresne Atmospheric Program – Indian Ocean (MAP-IO) program, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14929, https://doi.org/10.5194/egusphere-egu23-14929, 2023.
Previous studies showed that interaction between the atmosphere and sea is very important for simulating offshore wind, due to the effects of sea waves on momentum, mass and energy exchanges. In numerical weather prediction models, this effect is typically represented by a parameter known as roughness length. However, many atmospheric models do not take into account the impact of waves on roughness length over the sea.
In this study, we aimed to investigate the effects of waves on offshore wind simulation by applying some new roughness length formula in Weather Research and Forecasting (WRF) to consider wave characteristics in roughness length calculation. The simulations were compared with observations during some cases of misalignment and alignment of wind and wave directions at FINO1 station. We compared wind speed and wind power density of the simulated and observed data using met mast and lidar data.
How to cite: Mohammadpour Penchah, M., Bakhoday Paskyabi, M., and Bui, H.: Investigating the Impact of Sea Waves on Offshore Wind Simulation: A Study Using the WRF Model, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16033, https://doi.org/10.5194/egusphere-egu23-16033, 2023.
The location and the degree of instability (meandering) of the Gulf Stream have been suggested to influence, through air-sea interactions, the North Atlantic Jet Stream and weather patterns over Northern Europe. Although the Gulf Stream’s impact on the marine boundary layer (MABL) is well established, the associated mechanism(s) and timescale(s) are, however, debated. Taking advantage of a 24-member ensemble of ocean-only (12km) integrations in the North Atlantic, we devised an eddy-resolving (~10km) regional atmospheric model (WRF) step up where the same weather system feels different realizations of Gulf Stream turbulence. We compare the experiments forced with the given ensemble members (abundance of mesoscale eddies) with a unique ensemble mean SST (lack of mesoscale eddies) forced investigation to shed further light on the impact of Gulf Stream SST meandering on midlatitude winter storm track. We find that Gulf Stream meanders recharge/discharge the marine boundary layer with heat and moisture, thus preconditioning the atmosphere so that the passing atmospheric front modulates the produced rainfall. This effect is seen systematically in each member of the ensemble and surprisingly leaves its imprint on the precipitation averaged over a short time period (less than a month). The imprint of the meanders on the dynamical fields (pressure, velocities) is found to reach above the MABL but is less robust in the upper troposphere.
How to cite: Chakravorty, S., Czaja, A., Parfitt, R., and William, D.: The impact of Gulf Stream meanders on atmospheric fronts in a regional high-resolution atmospheric model. , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16171, https://doi.org/10.5194/egusphere-egu23-16171, 2023.
The uppermost 0-20m depth of the ocean within the mixed layer (ML) were investigated on diurnal scales using data collected during the EUREC4A campaign in the western tropical Atlantic. The results are compared against data from the global coupled Earth System model ICON. In both datasets is the diurnal impulse generator the penetrating shortwave solar radiation, heating the first meters of the ocean. During day on top of the ML a stably stratified near-surface layer, called the diurnal warm layer (DWL), can be formed. Depending on the wind conditions or the amount of incoming solar radiation the depth of such a DWL can reach from several centimeters to tens of meters. Associated to the stable stratification (and the wind) shear is produced which propagates down with time. At that point, the model and the observations start to differ. Using high-resolution current measurements of ADCP’s mounted on saildrones the detailed structure of the descending shear layer is observed. The cycle of shear instability leads the diurnal mixing cycle, typically by 2–3 h, consistent with the time needed for instabilities to grow and break (observed by microstructure measurements). In the morning, the turbulence decays and the upper ocean restratifies. At this point, wind accelerates the near-surface flow to form a new unstable shear layer, and the cycle begins again. Since the study area is located around 15°N, the excited layers are affected by the Coriolis force, which causes the descending shear layer to rotate around the inertial frequency of 1.8 days. Compared to the global coupled earth system model, these processes cannot be represented in such detail here. This leads to lower shear (and also mixing) at the different time and depth. Different model configurations show that even small differences in the upper 20m of the ocean, such as those observed, can lead to quite large changes in the model, e.g., a different strength of the ocean current system down to 1000m depth.
How to cite: Schuette, F., Lange, D., Putrasahan, D., Carrasco, R., L'Herguet, P., Zhang, D., Speich, S., von Storch, J.-S., and Karstensen, J.: The diurnal warm layer and its consequences for the upper ocean: from EUREC4A-OA observations and the global coupled ICON-ESM, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16379, https://doi.org/10.5194/egusphere-egu23-16379, 2023.
The ECMWF-ERA5 reanalysis is amongst the best products to access the hourly state and trend of the global Atmosphere, Wave field, and Ocean over several decades, for many scientists and in many studies. In the proposed presentation, we will compare the turbulent momentum and heat exchange flux values output from the reanalysis to corresponding estimates that were not assimilated in the model. Those estimates were computed from data collected with a wave following platform that was deployed in several basins since 2012, including the Chile-Peru upwelling region in 2014. Not only the fluxes and the bulk variables will be statistically compared, but the focus will also be laid on the sensitivity of the results to the surface current, to the proximity of coast and, where it applies, to the direction of the wind (onshore, offshore and parallel to the coast).
How to cite: Benjeddou, S., Denis Bourras, D., Dewitte, B., Luneau, C., and Fraunié, P.: Comparison of ECMWF-ERA5 turbulent Air-Sea Fluxes and related environmental variables to data from to the OCARINA wave following platforms, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16810, https://doi.org/10.5194/egusphere-egu23-16810, 2023.
Posters virtual: Mon, 24 Apr, 10:45–12:30 | vHall CR/OS
Gas transfer between ocean and atmosphere is largely governed by the turbulence in the topmost centimetres beneath the free surface. It has been frequently observed that areas of strong positive divergence of the surface-tangential velocity field correspond to efficient surface renewal and consequently increased transfer of gas across the interface. Patches of strong positive surface divergence occur in the form of intermittent upwelling events visible as ``boils'' on the surface.
It has been qualitatively observed that surface-attached ``bathtub'' vortices tend to appear at the edges of upwelling boils, hence a correlation between the density of these long-lived vortices and average surface divergence might be expected. Surface-attached vortices leave imprints on the surface which are particularly simple to detect: they live for a long time compared to turbulence turn-over, and their imprints are in the form of nearly circular dimples.
From direct numerical simulations, we show that a very high correlation exists between the time-dependent number of surface-attached vortices and the mean square of the surface divergence. A correlation coefficient of over 0.9 is found, where peaks in the number of vortices occur a little time after the peak in surface divergence, approximately half of the integral timescale of the bulk turbulence.
We use a newly developed method whereby the surface-attached vortices are identified with high precision and accuracy from their surface imprint only. Thus, observation of surface dimples can act as a proxy for surface divergence, with the prospect of remote sensing of gas transfer rate.
How to cite: Babiker, O., Bjerkebæk, I., Xuan, A., Shen, L., and Ellingsen, S. A.: Surface attached vortices as a proxy for gas transfer in free-surface turbulent flow, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15444, https://doi.org/10.5194/egusphere-egu23-15444, 2023.
