By bringing together experts from diverse disciplines, this session aims to provide a comprehensive platform for discussing the latest advances in AR science. We invite all contributions that aim at a better understanding of AR uncertainties, processes, and impacts across past, present, and future climates. Relevant topics of the session include, but are not limited to:
• Observation, identification, and monitoring of ARs
• Physical, dynamical, & microphysical aspects of ARs
• Aerosol & biochemical aspects of ARs
• Environmental and socioeconomic impacts of AR-induced weather extremes
• ARs as a component of compound events
• AR dynamics and impacts in understudied regions
• Role of ARs in the changing Cryosphere
• Forecasting of ARs
• ARs in past, present, and future climates
Orals: Fri, 2 May | Room 1.85/86
Recent studies of extreme precipitation and flood events affecting the Alpine area in northern Italy have revealed that besides the local contribution due to evaporation from the Mediterranean Sea, a relevant amount of moisture may move from remote areas towards the Mediterranean within long and narrow filament-shaped structures, known as atmospheric rivers.
High-resolution numerical simulations have demonstrated that the presence of an intense atmospheric river, whether coming from Africa tropical areas or from the Atlantic, represented a distinguishing aspect of those events, superimposed on the well-known mesoscale dynamic mechanisms of heavy precipitation over the Alps. The orographic uplift of water vapour transported by the atmospheric rivers represented a critical ingredient for the occurrence of extreme rainfall, and the characteristics of the atmospheric rivers determined the distribution and the intensity of the precipitation.
In order to investigate further the possible link between atmospheric rivers across the Mediterranean basin and high-impact weather, a detection algorithm, designed for the open oceans, has been adapted to the peculiar complex morphology of the region. It has been applied to conduct a climatological analysis on the presence of atmospheric rivers in the Mediterranean, exploiting ERA5 reanalysis, and to assess their relationship with extreme rainfall events over northern Italy during the last decades, exploiting a precipitation dataset with raingauge observations aggregated over civil protection warning areas. The study is undertaken in the framework of the national project ARMEX, funded by the Italian Ministry of Universities and Research, which involves also expertise in remote sensing and hydrological modelling to fully investigate characteristics and hydro-meteorological impact of atmospheric river over the national territory.
How to cite: Davolio, S., Sala, I., Comunian, A., Mastrangelo, D., Laviola, S., Monte, G., Tomassetti, B., Lombardi, A., Verdecchia, M., Grazzini, F., and Colaiuda, V.: Atmospheric rivers in the Mediterranean basin and heavy precipitation over northern Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8024, https://doi.org/10.5194/egusphere-egu25-8024, 2025.
The dynamics of atmospheric moisture transport plays a dominant role in understanding the physical mechanisms that lead to extreme precipitation events (EPEs). In mid-latitudes, 90% of poleward moisture transport occurs along transient channels known as atmospheric rivers. However, due to the complex interactions of regional weather systems, they are challenging to define, detect, and analyze in tropical regions. In this context, the PIK Atmospheric River Trajectories (PIKART) catalog offers a unique capability to detect coherent channels of intense moisture transport, particularly in the tropical region. These are referred to as anomalous moisture transport pathways (AMTPs) to ensure clarity and avoid ambiguity. The existence of AMTPs in the tropics remains an open question and the role of their differentiated atmospheric dynamics in driving EPEs across the Indian subcontinent is yet unclear. To address this, we employ a novel database of EPEs created using the weather extremity index coalesced with the peak over threshold method, together with the PIKART catalog. We systematically identify the co-occurrence of AMTPs and EPEs in the Indian subcontinent. Our results reveal that among the top 100 EPEs, more than 47% displayed AMTPs. To understand the contribution of AMTPs to the severity of EPE, we also present a case study of the 2018 Kerala floods, for which the presence of an AMTP has been documented. Although previous studies identified an AMTP on August 13, 2018, we detected the occurrence of an earlier one on August 9, 2018, preceding the landfall of the event that unfolded between August 13 and 17, 2018. The decomposition of moisture contributions indicates that over 45% of the total moisture is attributed to this earlier AMTP trajectory, suggesting enhancement in the monsoon circulation. Our results shed light on the concept of AMTP in the tropics and contribute to comprehend its influence on climate extremes, a critical task to improve risk management and develop mitigation strategies.
How to cite: Ganpathiraju, S. A., M. Vallejo-Bernal, S., Marwan, N., and Rathinasamy, M.: Investigating the Role of Anomalous Moisture Transport in Indian Subcontinent's Extreme Precipitation Events: A PIKART Perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5904, https://doi.org/10.5194/egusphere-egu25-5904, 2025.
Atmospheric rivers (ARs) are filaments of enhanced moisture in the atmosphere, which often produce intense or even extreme precipitation when the enormous amounts of water vapor in them are forced upwards. In this sense, one of their most studied and debated properties is the origin of the moisture they transport. Although some studies have identified sources using different diagnostic tools for specific AR cases, it remains unclear whether tropical or extratropical contributions are generally more prevalent, and even the AR definition in the Glossary of Meteorology reflects this lack of consensus.
To fill this gap, a climatology of moisture sources for precipitation in ARs is needed. There are a variety of moisture source diagnostics that can be employed to address this issue. Here we use the Lagrangian model FLEXPART together with an implementation of the Dirmeyer and Brubaker, (1999) methodology, which we previously validated using the WRF with Water Vapor Tracers (WRF-WVTs) model. This allows us to efficiently simulate air particle trajectories and compute moisture sources for precipitation within a wide range of ARs with a Lagrangian methodology, while maintaining consistency with the WRF-WVTs model, assumed to be one of the most accurate moisture tracking tools. Preliminary results reveal a wide diversity of moisture sources, including both oceanic and continental regions, with substantial variability in their contributions across different AR cases. Importantly, our findings also indicate a less relevant role of tropical moisture than previously known. Ultimately, this highlights the complexity of the moisture uptakes in ARs.
Dirmeyer, P. A. and Brubaker, K. L.: Contrasting evaporative moisture sources during the drought of 1988 and the flood of 1993, J. Geophys. Res. Atmospheres, 104, 19383–19397, https://doi.org/10.1029/1999JD900222, 1999.
How to cite: Crespo-Otero, A., Insua-Costa, D., and Míguez-Macho, G.: Unravelling the sources of moisture for precipitation in atmospheric rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12461, https://doi.org/10.5194/egusphere-egu25-12461, 2025.
Atmospheric rivers (ARs) are narrow, elongated corridors of concentrated moisture that transport substantial amounts of water vapour from the tropics to the mid-latitudes. These meteorological phenomena are known to significantly influence extreme precipitation events and are often linked to major flood occurrences. Despite their recognized importance in regional hydrology, the overall contribution of ARs to global flood risk—the hazard posed by extreme precipitation events—has not been comprehensively quantified. In this study, we assess the relationship between ARs and extreme hydrological events using data from 2686 largely regulation-free catchments distributed across the globe. Our findings reveal that on a regional scale, ARs are responsible for over 70% of the largest precipitation and streamflow events in the last four decades. Furthermore, AR-related precipitation leads to a significant reduction in the recurrence intervals of these extreme events, increasing the likelihood of large-scale flooding by a factor of 2 to 4. In certain regions, such as parts of North America, Europe, and Australia, rare flood events are up to 12 times more likely when ARs are present. These results underscore the critical role that ARs play in driving the frequency and severity of extreme hydrological events globally. Our findings highlight the need for greater attention to the influence of ARs on flood risk, particularly as climate change may alter their frequency and intensity in the future.
How to cite: Pradhan, S., Wasko, C., and Peel, M.: Global scale impact of atmospheric rivers on the severity of flooding , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2964, https://doi.org/10.5194/egusphere-egu25-2964, 2025.
Atmospheric Rivers (ARs) are narrow and long bands of high water vapour content, which largely originate in the tropics or subtropics and propagate into mid- and high-latitudes. They can bring beneficial rain and snow but, in particular the most intense, can lead to catastrophic flooding and loss of life. One of such occurrences in the Middle East in mid-April 2023 is investigated using model and observational data. The high-resolution (2.5 km) simulation put in evidence narrow (5-15 km) and long (100-200 km) convective structures within the AR, known as AR rapids, which produced heavy precipitation (>4 mm hr-1), further enhanced by gravity waves that developed over the high terrain in western Saudi Arabia, and propagated at high speeds (>30 m s-1). ARs are occurring more frequently in the Middle East as they are globally, and with increased atmospheric water vapour in a warming climate, AR rapids may be even more destructive.
How to cite: Francis, D., Fonseca, R., and Nelli, N.: Atmospheric River Over the Middle East , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14684, https://doi.org/10.5194/egusphere-egu25-14684, 2025.
Atmospheric rivers (ARs) play an important role in both the global and regional climate systems. While there is extensive research on ARs and their relationship to precipitation in North America and East Asia, the role of ARs in the regional climate of Scandinavia remains understudied.
In this study, we investigated the characteristics of ARs making landfall over Scandinavia, their influence on regional precipitation, and how they are affected by the North Atlantic Oscillation (NAO). To achieve this, we analysed the ARs between 1980 and 2019 detected by four different AR Detection and Tracking algorithms (ARDT), from the Atmospheric River Tracking Method Intercomparison Project (ARTMIP). Combined with ERA5 reanalysis precipitation data, we quantified the AR related precipitation over the region.
We found that ARs are present during up to 35% of the total annual precipitation in Scandinavia, with the average AR-associated rainfall rate exceeding the non-AR rates. Clustering the ARs that intersect Scandinavia revealed four main AR patterns. For the two most frequent patterns, located in southern Scandinavia, ARs account for up to 32% of the total annual precipitation. Furthermore, for all patterns, AR activity reaches a maximum during autumn and whilst the NAO is in a strong positive phase. The results from the four ARDTs show similar spatial patterns, but with a notable difference in the magnitude of AR influence on precipitation. Our findings indicate that ARs are an important factor in Scandinavian precipitation, and highlight the value of using multiple ARDTs to obtain more robust results.
How to cite: Holmgren, E. and Chen, H.: Spatial and temporal characteristics of atmospheric rivers in Scandinavia and their influence on the regional precipitation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3577, https://doi.org/10.5194/egusphere-egu25-3577, 2025.
Atmospheric rivers (ARs), responsible for extreme weather conditions, are mid-latitude systems that can cause significant damage to coastal areas. While forecasting ARs beyond two weeks remains a challenge, past research suggests potential benefits may come from properly accounting for the changes in sea surface temperature (SST) through air–sea interactions. In this paper, we investigate the impact of ARs on SST over the North Pacific by analyzing 25 years of ocean reanalysis data using an SST budget equation. We show that in the region of strong ocean modification, ocean dynamics can offset over 100% of the anomalous SST warming that would otherwise arise from atmospheric forcing. Among all ocean processes, ageostrophic advection and vertical mixing (diffusion and entrainment) are the most important factors in modifying the SST tendency response. The SST tendency response to ARs varies spatially. For example, in coastal California, the driver of enhanced SST warming is the reduction in ageostrophic advection due to anomalous southerly winds. Moreover, there is a large region where the SST shows a warming response to ARs due to the overall reduction in the total clouds and subsequent increase in total incoming shortwave radiation.
How to cite: Hsu, T.-Y., Mazloff, M., Gille, S., Freilich, M., Sun, R., and Cornuelle, B.: Response of sea surface temperature to atmospheric rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20603, https://doi.org/10.5194/egusphere-egu25-20603, 2025.
Recently, the water vapour atmospheric river (AR) concept was extended to aerosols, introducing the term aerosol atmospheric river (AAR) into the literature. Equivalently to ARs, AARs are narrow and transient filaments of intense aerosol transport in the lower troposphere. The Iberian Peninsula (IP) is one of the regions regularly affected by ARs and is also frequently impacted by Saharan dust outbreaks. While the impacts of ARs in the IP were extensively studied, there is a lack of regional studies on the impact of AARs in the IP. Moreover, the relationship between ARs and AARs in the IP has not yet been investigated. Therefore, this work aims to better understand the relationship between ARs and AARs in the IP and to quantify the co-occurrence of these phenomena. In this sense, a modified algorithm originally designed to detect ARs was applied to the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis in order to identify the AARs that affected the IP over a 20-year period. Five aerosol types were used: dust, sea salt, sulphate, organic carbon and black carbon. In this presentation, we will show and discuss the climatology, the seasonality, and the characteristics of each type of Iberian AAR and how often these events are associated with ARs. This work contributes to a better understanding of the differences between ARs and AARs, as these phenomena share similarities but can also have different origins and trajectories.
This work was supported by the Portuguese Foundation for Science and Technology (FCT) through a PhD grant (2023.03574.BD) for Diogo Luís.
How to cite: Luís, D., Gorodetskaya, I., and Gama, C.: Relationship between atmospheric rivers and aerosol atmospheric rivers in the Iberian Peninsula, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18254, https://doi.org/10.5194/egusphere-egu25-18254, 2025.
Atmospheric Rivers (ARs) play a critical role in the Arctic climate system, providing the majority of water vapor transport into the Arctic. The potential of such events to impact especially the ice-covered regions of the Arctic have been explored in recent studies: ARs can trigger surface melt of the Greenland ice sheet and slow the seasonal recovery of the Arctic ice sheet. Furthermore, the low Arctic sea-ice extents of the years 2012 and 2020 could be linked to a more frequent occurrence of ARs. These case studies highlight the warming effect of individual cases of ARs.
We statistically investigate the warming effect of ARs on the Arctic sea-ice and ocean surface by examining anomalies in the atmospheric part of the surface energy budget (SEB). This climatological analysis is based on the ERA5 reanalysis from 1979 to 2021. ARs are detected using the algorithm by Guan and Waliser. Overall, a net energy gain of the surface associated with the occurrence of ARs is found, with the highest anomalies in winter over the open ocean. For a deeper understanding of the impact, complementary information on the climatological relevance of these events for the SEB is provided. Furthermore, we analyze the physical processes leading to the AR-related SEB anomalies, explaining the seasonal changes and the dependence of the anomalies on the surface type.
Within the rapidly changing Arctic climate, also changes in AR occurrence and their impact on the SEB can be expected. We investigate these changes by comparing the “old Arctic” (1979-1999) with the “new Arctic” (2000-2021). An overall increase in the occurrence frequency of ARs is found. Changes in the AR-related SEB anomalies are mostly linked to sea-ice decline.
How to cite: Tiedeck, S. and Rinke, A.: Arctic Atmospheric Rivers: An in-depth Investigation of their Impact on the Surface Energy Budget, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18198, https://doi.org/10.5194/egusphere-egu25-18198, 2025.
The Arctic has witnessed significant sea-ice melt and rising temperatures as major indicators of climate system alterations. As a severe weather event conveying heat and moisture from lower latitudes to the higher, atmospheric rivers (ARs) can lead to significant sea-ice loss and Arctic warming. Sea ice thickness is applied in this study to quantitatively explored the thermodynamic and dynamic impacts of ARs in winters from 2000 to 2020. ARs from the North Atlantic (AAR) and North Pacific (PAR) account for 44% of AR events and 40% of AR-driven sea-ice loss. The AR-induced melting process occurs in three successive stages. In Stage I, warm, moist air driven by dipole circulation anomalies ahead of AR causes sea ice melting, with thermal effects accounting for 53% for AAR and 58% for PAR. Stage II starts when the AR enters the Arctic and ends as its moisture transport weakens. Early sea-ice loss is driven by wind dynamics, while poleward progression elevates warm, moist air, forming clouds that intensify melting thermodynamically. This stage sees the most significant sea-ice melt, dominated by dynamic effects for AAR (59%) and thermodynamic effects for PAR (55%).In Stage III, as AR moisture dissipates, sea-ice melt continues for about a week, primarily driven by thermodynamic effects. Accompanied by the above three stages, the anticyclonic circulation anomaly on the right side of where AR is headed can also enhance downdrafts and melt perennial ice. By contrast, Pacific-channel ARs have a higher impact on the central Arctic than their Atlantic counterparts, suggesting extensive responses to climate variability.
How to cite: Gong, Z.: Dynamic and thermodynamic impacts of atmospheric rivers on sea-ice thickness in the Arctic since 2000, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3436, https://doi.org/10.5194/egusphere-egu25-3436, 2025.
Processes controlling the timing of the Arctic sea ice melt onset still remain unclear, but possible factors include variations in atmospheric circulation patterns and anomalies in clouds, moisture and surface energy budget, all of which are linked to narrow bands of warm and moist-air advection. These filaments, accounting for the majority of the poleward moisture transport, are called Atmospheric Rivers (ARs). Although spring is an important transition period for the sea ice evolution, there are hardly any in-situ observations in the Arctic Ocean for that period. To narrow down the knowledge gaps, the ARTofMELT expedition took place on the Swedish research Icebreaker Oden in the Fram Strait in May-June 2023 with two main objectives: to study processes leading up to the melt onset of Arctic sea ice and to investigate the role of ARs in affecting this timing. This study is motivated by the ARTofMELT expedition, during which the observed surface temperature exceeded the melting point on the 10th of June 2023 – much later than expected. Questions raised were “was this an anomalously late melt onset?” and “if yes, why?”. To address these questions, we put the year 2023 into a climatological (1981-2020) perspective by linking satellite-derived melt-onset (MO) dates with large-scale circulation features. Due to lack of MO-dates along the track in June 2023, the location of Oden during ARTofMELT is represented by a “Fram Strait sector”. Years are categorized into early and late MO-years based on the relative number of significant MO-anomalies within the sector.
The melt onset timing in the sector within the climatological period has a significant negative trend of -5 days in 10 years. In spring 2023, the average melt onset occurs on 8 June, corresponding to a MO-anomaly of almost 2 weeks relative to a transient climatology. As nearly 60 % of all grid-points obtain significant positive MO-anomalies and only a negligible fraction has significant negative MO-anomalies, we conclude that the melt onset in the sector region during ARTofMELT in spring 2023 was anomalously late.
The period before the MO in the sector was characterized by significant negative SLP anomalies over the whole Arctic Ocean and positive anomalies in SLP and atmospheric blocking over Eurasia. These circulation anomalies were associated with a strong cyclonic activity along the sea ice edge, directing warm and moist air, and most of the ARs, east of Svalbard into the BKS region – leading to an early MO there. The central Arctic Ocean was anomalously dry. The circulation patterns weakened and rather normal conditions prevailed during the MO period in the Fram Strait, where the MO was finally triggered by a transient AR on 10 June 2023.
Analysis between six most extreme early and late MO-years reveal that specific circulation patterns favoring moist and warm air transport towards and the occurrence of ARs within the Fram Strait sector are of more importance in determining the timing of MO for extreme early MO-years, whereas extreme late MO-years seem to be due to an absence of such large-scale features.
How to cite: Murto, S. and Tjernström, M.: ARTofMELT spring 2023 expedition: Investigating the Arctic sea ice melt onset in the context of climatology and atmospheric circulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1741, https://doi.org/10.5194/egusphere-egu25-1741, 2025.
The Arctic region is strongly impacted by climate change. Poleward transport of warm and moist air is one of the mechanisms contributing to accelerated Arctic wintertime warming. Warm and moist air intrusions (WAIs) into the Arctic are often associated with warm extremes and positive surface energy balance (SEB) anomalies by increased longwave downward radiation (LWD), impacting sea ice extent and recovery. WAIs are expected to increase in frequency in a warming climate until the end of the century, but uncertainties remain regarding their life cycle characteristics, as well as their local impacts and seasonality.
This study focusses on intrusion events that travel from the Greenland and Barents Seas far through the central Arctic. These transarctic WAIs are identified as anomalously high column-integrated water vapor transport (IVT) events and are tracked in space and time with the MOAAP algorithm (Prein et al. 2023).
Focusing on boreal winter (DJF) the occurrence, impacts and life-cycle characteristics of transarctic intrusion events along their path are initially studied using ERA5 data. A first analysis identified 14 transarctic WAIs between 1979-2022, which on average travel 7500 km within a common lifetime of five days. We show that these events are associated with increased integrated water vapor (IWV), LWD, precipitation, and near-surface wind speeds over Arctic sea ice and that these effects become less pronounced towards the end of the WAIs lifecycle.
Furthermore, we find that during the transarctic WAI’s onset stage in the Greenland and Barents Seas, the associated transport of moist air masses towards the central Arctic is dynamically driven by a strong Icelandic low linked to a positive NAO state or a Scandinavian blocking. As these pressure patterns gradually shift northwards, the WAIs are directed through the Arctic, eventually reaching the Beaufort or East Siberian Seas.
The upcoming analysis will be extended by using data from regional Arctic model simulations with the atmospheric model ICON. Those are forced with ERA5 and two selected global CMIP6 climate models under the SSP370 scenario. The latter represent two distinct Arctic warming scenarios until the end of the century. This allows to assess future changes of transarctic WAIs and their impacts under different future Arctic warming storylines.
How to cite: Lüdke, E., Landwehrs, J., Riebold, J., Tiedeck, S., and Rinke, A.: Wintertime Transarctic Warm and Moist Air Intrusions Tracked in Present and Future Climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-733, https://doi.org/10.5194/egusphere-egu25-733, 2025.
Despite their rarity, atmospheric rivers (ARs) bring powerful impacts to Antarctica when they make landfall on the ice sheet. Antarctic ARs contribute 10% of the annual precipitation and are major drivers for heatwaves, foehn events, and surface melting on ice shelves. While snowfall is currently the dominant impact of Antarctic ARs, helping to offset sea level rise due to ice discharge from West Antarctica, the relative contribution of ARs to snowfall, rainfall, and surface melt may change in a warming climate, along with the frequency and intensity of AR events themselves, motivating the study of these rare, impactful events. In this study, we examine the occurrence of Antarctic AR families, in which two or more ARs occur in rapid succession in a region. While individual ARs have been shown to have pronounced and widespread impacts in Antarctica, latent heat release from ARs in a family can reinforce associated downstream high-pressure systems to produce extended, high impact AR conditions on the ice sheet, including multiple days of intense snowfall and temperatures above the melting point. Here we present initial results from an Antarctic-wide study of the occurrence and impacts of AR family events. First, we use a density-based clustering algorithm to classify AR events as objects from an Eulerian, Antarctic-specific detection tool based on MERRA-2 reanalysis. From this, we construct a database of AR events around Antarctica from 1980-2022, with information on the location, duration, and landfall (if it occurred) for each AR. Then, we cluster the AR events by location and time once more, to identify the occurrence of AR family events. We explore the sensitivity of the number of AR family events detected, and the number of ARs per family, to the chosen aggregation period (two to six days) and distance parameter (500 – 1000 km). Finally, we utilize a novel atmospheric Rossby wave breaking detection tool to compare the frequency of cyclonic and anticyclonic wave breaking events over the Southern Ocean to the frequency of AR family and non-family events. Ultimately, our study aims to diagnose the occurrence, synoptic drivers, characteristics, and impacts of AR family events on the Antarctic Ice Sheet in the last four decades, to provide a baseline assessment of how these extreme events can compound to produce lasting, high-impact conditions.
How to cite: Maclennan, M., Butler, J., Baiman, B., LaChat, G., and Shields, C.: Identifying Antarctic Atmospheric River Families, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7213, https://doi.org/10.5194/egusphere-egu25-7213, 2025.
Understanding the regional and temporal variability of atmospheric river (AR) seasonality is crucial for preparedness and mitigation of extreme events. While ARs were thought to peak in winter, recent research shows they exhibit region-specific seasonality and are heavily influenced by the chosen detection algorithm. This study examines the link between the year-to-year consistency of peak AR activity to the presence of a dominant seasonal pattern, considering both location and algorithm choice. Regions are categorized by their temporal characteristics: consistent patterns (e.g., India, Central Asia), patterns with occasional outliers (e.g., British Columbia coast, Gulf of Alaska), and regions lacking a clear dominant peak season (e.g., South Atlantic, parts of Australia). Hence, not all regions display a consistent seasonal cycle of AR activity. This study quantifies the extent to which a region experiences a dominant peak season of AR activity (or lacks one) and offers insights to enhance decision-making in water management, natural hazard preparedness, and forecasting. Furthermore, given our finding that detection algorithms influence the peak season of AR activity, we also examine two diagnostic variables representative of moisture transport to corroborate our results. Integrated Vapor Transport, which captures meridional and zonal moisture transport, and Moist Wave Activity, representing moisture intrusions from lower to higher latitudes, are examined. Our analysis indicates that inconsistencies in the seasonal cycle of AR activity are not solely due to discrepancies in detection algorithms but also arise from changes in moisture transport.
How to cite: Kamnani, D., O'Brien, T. A., Smith, S., Staten, P. W., and Shields, C. A.: Regional and Temporal Variability of Atmospheric River Seasonality: Influences of Detection Algorithms and Moisture Transport Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2319, https://doi.org/10.5194/egusphere-egu25-2319, 2025.
The U.S. National Centers for Environmental Information (NCEI) is sponsoring development of an atmospheric river (AR) climate data record (CDR) to serve as a valuable resource for the scientific, water management, and decision-making communities across the Western US (and soon, globally). The CDR uses a novel combination of two techniques: (1) the AR Scale, which broadly characterizes the AR strength from 1-5 based on the peak integrated water vapor transport (IVT) and duration of AR conditions (i.e., IVT ≥ 250 kg m-1 s-1) at a given location, and (2) the tARget algorithm–a tool that uses climatological, geometric, and directional thresholds to identify ARs. Since the AR scale has no geometric criteria (and thus ranks non-AR events such as tropical cyclones, cutoff lows, and monsoons) and tARget does not provide characterization of AR strength, these two methods complement each other, with AR Scale-identified events “filtered” by tARget. This presentation highlights the resulting data and effects of this “filtering” through selected cases, long-term climatology, and interannual variability across various global regions. In addition, we explore attribution of precipitation to AR events identified in the CDR. All historical atmospheric data is sourced from the ERA5 reanalysis.
How to cite: Slinskey, E., Rutz, J., Guan, B., and Ralph, F. M.: The NCEI Climate Data Record for Atmospheric Rivers: Initial Results over the Western United States, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6689, https://doi.org/10.5194/egusphere-egu25-6689, 2025.
Posters on site: Fri, 2 May, 08:30–10:15 | Hall X5
The increasing frequency and severity of hydrological extremes, such as heavy precipitation events, are significant challenges for human-environmental systems. Atmospheric rivers (ARs) are key drivers of these extremes, but the complex transport patterns of ARs at global scale remain underexplored. Our research introduces a novel network-based approach to studying global AR dynamics, applying methods from complexity science to reveal the “global road network” of ARs.
In analogy to terrestrial river networks, the pathways that ARs follow through the Earth’s atmosphere can be effectively represented by a transport network. Generally, the paradigm of complex networks encodes interactions between the units of a system through interlinked nodes. Recent applications illustrate that complex networks have provided novel insights into climate teleconnection patterns, synchronization of extremes and vegetation-atmosphere feedbacks. We draw on the vast array of existing methods from complex network theory to reveal the global atmospheric river network. We define it on a hexagonal grid to avoid distortions due to the Earth’s spherical geometry. Multiple AR catalogs can be integrated seamlessly. To quantitatively assess the significance of a transport property, the framework is equipped with a hierarchy of data-adaptive null models that are based on random walker ensembles.
We dissect the global transport infrastructure of ARs which reveals prominent AR pathways, regions of complex multi-directional transport, the predictability of single AR tracks, and scale-dependent spatial clusters. We demonstrate that there exists complexity above and beyond the previously identified four main branches of AR transport. These main oceanic bands can be decomposed into significant sub-branches. Exploiting all these novel tools to characterise AR transport, we unveil how the AR network is evolving in a changing climate. This talk underscores the potential of complexity science to advance our understanding of ARs as critical components of the integrated human-Earth system.
How to cite: Braun, T., Vallejo-Bernal, S. M., Marwan, N., Kurths, J., Sippel, S., and Mahecha, M.: The Global Atmospheric River Network: A Complex Network Approach to Global Moisture Transport Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3695, https://doi.org/10.5194/egusphere-egu25-3695, 2025.
The critical role of atmospheric rivers (ARs) in the global water cycle, along with their intensification under global warming, underscores the urgency of understanding and predicting their dynamics and impacts at both regional and global scales. Despite significant advances, this endeavor remains challenging because ARs lie at the interface of weather and climate. These synoptic-scale systems produce short-term, localized impacts while shaping long-term global patterns of moisture, wind, and precipitation. AR genesis and evolution emerge from interactions within the coupled ocean-atmosphere system, while AR-induced precipitation can lead to natural disasters through land-atmosphere interactions. By transporting vast amounts of moisture over great distances, ARs establish teleconnections that influence weather across thousands of kilometers. At the same time, their activity is shaped by large-scale climate phenomena such as the El Niño–Southern Oscillation and the Pacific Decadal Oscillation. Advancing AR science, therefore, requires treating ARs as integral components of the Earth system and unraveling their interactions across a broad range of spatial and temporal scales.
In this talk, we present and discuss the paradigm of complexity science and the exciting opportunities it offers for advancing AR science. Building on a solid foundation of dynamical systems, stochastic climate theory, and network theory, complexity science integrates nonlinearities, feedbacks, and uncertainties into the study of ARs. By employing novel methods such as event synchronization, climate networks, and probabilistic causation, complexity science provides powerful tools to investigate non-local interactions, uncover hidden dynamics, and refine impact attribution in AR research. To ensure the robustness of findings, complexity science integrates null models, hypothesis testing, confidence bounds, and sensitivity analyses. Emerging research avenues, such as AR networks, community detection, low-order modeling, and tipping dynamics, can now be explored through the lens of complexity science. By establishing a rigorous theoretical and methodological foundation, complexity science paves the way for innovative research on AR dynamics, impacts, and prediction.
How to cite: Vallejo-Bernal, S. M., Braun, T., Marwan, N., Bastos, A., Mahecha, M. D., and Kurths, J.: Atmospheric Rivers as Interacting Elements of the Earth System: A Complexity Science Perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14595, https://doi.org/10.5194/egusphere-egu25-14595, 2025.
Extreme precipitation and wind events in Western Europe are driven by Atmospheric Rivers (ARs) developing over the North Atlantic Ocean. While extensive research has been conducted on the atmospheric dynamics of ARs in this region and their connection with the North Atlantic Storm Track, gaps persist in understanding how oceanic variability influences AR activity, particularly in the eddy-rich environment of the Gulf Stream extension. The enhanced ocean heat supply and high mesoscale eddy activity over these western oceanic currents increase the surface latent heat flux in the area, thereby increasing moisture availability in the lower atmosphere and potentially facilitating AR genesis.
This study focuses on evaluating the status of mesoscale eddies and oceanic conditions within the Gulf Stream extension and their downstream impact on AR activity. To achieve this, we employ a high-pass Fourier Filter Transformation to isolate and quantify the mesoscale eddy activity (smaller than ~500 km) of the Gulf Stream extension region in a high-resolution (0.125º) satellite product for the sea surface height. Additionally, we utilise different observational products (OAFlux, ARGO and RAPID) to quantify the surface heat fluxes, the ocean heat content in the Gulf Stream extension region and the oceanic heat supply through the Florida Straight. Finally, we identify and track Atmospheric Rivers in the ECMWF reanalysis ERA5 dataset over the North Atlantic.
Our analysis provides a spatial and temporal cross-correlation analysis between the Gulf Stream state and the AR activity downstream. Furthermore, we investigate temporal lags between various oceanic conditions and their impact on ARs, thereby identifying oceanic precursors for AR genesis. Consequently, our study establishes a novel statistical relationship between Gulf Stream state and AR activity, with a particular emphasis on the role of mesoscale features. This includes a comprehensive characterisation of mesoscale eddy activity within the region, contributing to a deeper understanding of the mechanisms driving AR formation and propagation in Western Europe.
How to cite: Lopez-Marti, F., Czaja, A., Messori, G., Wu, L., and Rutgersson, A.: Gulf Stream Ocean Conditions Influence on Atmospheric Rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9886, https://doi.org/10.5194/egusphere-egu25-9886, 2025.
