Linking Air-Sea Fluxes to Extratropical Cyclone and Atmospheric River Development

Latent (LHF) and sensible heat fluxes (SHF) within the marine boundary layer are believed to significantly influence the genesis and evolution of Extratropical Cyclones (ETCs) and Atmospheric Rivers (ARs, often associated with ETCs in the midlatitudes). However, consistent observations of air-sea interactions using in-situ observatories are limited in time and space. Traditional polar-orbiting satellites can miss large swaths in the lower midlatitudes due to their orbits, resulting in daily coverage gaps in areas where robust fluxes occur and change rapidly. Satellite missions like CYGNSS (Cyclone Global Navigation Satellite System) have addressed these gaps by providing improved observations over the lower midlatitudes of air-sea interactions, emphasizing the need for more data. Enhanced observations of air-sea processes, combined with data on cloud and precipitation structures within ETCs and ARs from other satellites like GPM and MODIS, can help link the correlations between surface heat fluxes and changes in mesoscale features within these synoptic-scale systems. Previous studies have shown the correlation of observed surface heat fluxes with increases in precipitation and cloud thickness along the frontal regions. However, they primarily examined the connections between ETCs and ARs when LHF and SHF were at their strongest or during the peak intensity of the system rather than during its early formation (or just before formation) when these fluxes might be at their strongest.

Furthermore, recent studies have investigated, through idealized models, how surface heat fluxes in an ETC can influence the development of ETCs and ARs upstream of the primary cyclone, leading to successive ETCs, often described as a family or temporal clustering of ETCs and ARs. This clustering can result in significant and excessive precipitation in various regions, including the United States West Coast in January 2023, where successive ARs persisted for over a month. Enhanced observations of real-world conditions can improve our understanding of the interactions within these systems. This presentation will highlight the role that air-sea interactions may play during the genesis and early evolution of ETCs and ARs, their correlations with changes in cloud and precipitation structures, the upstream impacts, and the foundation for demonstrating that air-sea interactions directly influence the development of these systems.