Regional aspects and global signatures of ARs

Chairs: Christine Shields, Maximilano Viale

Atmospheric rivers are broadly and globally defined as long, narrow corridors of moisture transport. However, from a regional perspective, AR characteristics, metrics, and impacts can vary depending on the regional features through which they flow, such as topograpy and land or ocean surface types. Comparing what is common across all ARs, versus what is unique to specific locales, is essential to understand, predict, and project ARs and their impacts now and into the coming decades. Exploring regional differences provide insights into understanding ARs as a global phenomenon.

ARs and water extremes: from drought to flood & water management

Chairs: Kimberley Reid, Ross Blamey

Atmospheric Rivers are responsible for most of the atmospheric moisture transport between the wet tropics and dry poles. When ARs make landfall, they can bring beneficial rainfall that is vital for replenishing water supplies or cause too much rain triggering floods and landslides. On the other hand, a lack of ARs can lead to drought in some parts of the world. AR scientists around the globe are researching how and why these weather systems affect water extremes and working closely with stakeholders to better manage precious water supplies.

Forecasting of ARs from short to seasonal time scales

Chairs: David Lavers, Jason Cordeira

Atmospheric rivers are a leading source of extreme precipitation and flooding, motivating a need for improved short-term weather forecasts to seasonal outlooks. Skillful forecasts of ARs across these timescales supports a range of applications such as flood risk mitigation, emergency response, water resources management, and situational awareness. Continued advances in observations, data assimilation, and modeling are critical for improving forecast skill and extending predictability across these timescales.

Observing, identifying, and monitoring of ARs

Chairs: Anna Wilson, Ryan Rickert

Observations and accurate identification of ARs are critical to understand baseline information regarding their frequency, intensity, and impacts. Continuous monitoring of ARs supports early warning, improves forecast skill, and informs decision-making for flood risk reduction, water supply management, and infrastructure resilience. Observations can initialize numerical weather prediction models. They can also be used to diagnose model biases and then to guide the improved representation of underlying parameterizations, leading to more reliable forecasts of atmospheric rivers and their impacts.

Physical, dynamic, and microphysical aspects of ARs

Chairs: Sara M. Vallejo-Bernal, Rene Garreaud

Atmospheric rivers (ARs) are shaped by interacting physical, dynamical, and microphysical processes that govern their formation, evolution, and impacts. The physical structure of ARs controls their moisture and energy transport, the dynamics determine their trajectories and lifecycles, and microphysical processes regulate how efficiently moisture is converted into precipitation. Understanding these coupled aspects is therefore essential for characterizing AR evolution, improving their representation in weather and climate models, and attributing their impacts.

Aerosol and biogeochemical aspects of ARs

Chairs: Diogo Luís, Diana Francis

Although ARs are best known for their role in water vapor transport, they also act as dynamic conveyors of aerosols and biogeochemical constituents across vast distances. By transporting particles like dust, anthropogenic pollutants, as well as microorganisms, ARs influence cloud microphysics, radiative balance, and precipitation efficiency. Their deposition onto terrestrial, marine and cryospheric surfaces supplies critical nutrients, which drive ecosystem productivity, carbon cycling and surface energy balance. Understanding these coupled physical, chemical, and cryospheric processes is essential for improving predictions of AR impacts in a changing climate.

Role of ARs in the changing cryosphere

Chairs: Michelle Maclennan, Harald Sodemann, Irina Gorodetskaya

Atmospheric rivers play an increasingly important role in impacting the cryosphere under a warming climate. When these systems make landfall in polar and high-mountain regions, they can drive rapid surface energy fluxes through warm air advection, cloud radiative effects, and precipitation phase changes. Over ice sheets and glaciers, ARs are strongly linked to episodic melt eventsand also anomalous snowfalls. As AR frequency and intensity shift with climate change, their dual role, both building and eroding the cryosphere, is becoming a critical factor in future sea-level rise and freshwater availability.

ARs in past, present, and future climates

Chairs: Michael Warner, Marty Ralph

Examining ARs across timescales, from paleoclimate reconstructions to current observations and future projections, helps clarify how their frequency, intensity, and impacts evolve in a warming climate. This integrated perspective is essential for improving forecasts, refining climate models, and informing water management and flood risk strategies. It also creates a common framework for researchers and practitioners to align science with operational needs and long-term resilience planning.

Impacts of ARs on the environment and society, including in the context of
compound events

Chairs: Thomas Corringham, Alexandre Ramos

ARs bring beneficial water supply, but they also drive flooding, landslides, infrastructure disruption, ecosystem impacts, and cascading risks when they interact with other hazards such as storm surge, high river flows, saturated soils, or wildfire-affected landscapes. Advances in AR observation and forecasting can strengthen decision-making by providing communities, water managers, emergency responders, and other stakeholders with actionable information for rapid response, risk reduction, and increased resilience.

ARs and the Ocean: from physical drivers to biodiversity impacts

Chairs: Alizee De Groodt, Sharath Thota

ARs are key weather drivers inextricably linked to intense ocean-atmosphere interactions. Characterised by strong, consistent low-level winds, they generate large air–sea fluxes of momentum, heat, and moisture, altering the state of the ocean by driving mixed-layer deepening, sea surface temperature anomalies and strong onshore currents. These physical changes cascade through upper-ocean mixing and nutrient cycling, affecting species productivity, distribution, and biodiversity. Connecting ARs forcing to ocean state changes and marine ecosystem responses is fundamental for predicting ecosystem resilienceand informing decision-making and management strategies.