Air-Sea Flux Influences on Extratropical Cyclone and Atmospheric River Mesoscale Development and Upstream Temporal Clustering

Latent and sensible heat fluxes (LHF and SHF, respectively) within the marine boundary layer are believed to play a significant role in 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 with in-situ observatories are limited in both time and space, and traditional polar orbiting satellites may miss large swaths in the lower midlatitudes due to their orbits, leading to daily gaps in coverage where the most robust fluxes often occur and change rapidly. Satellite missions like CYGNSS (Cyclone Global Navigation Satellite System) have filled in data gaps by providing improved observations over the lower midlatitudes of air-sea interactions. These improved observations of air-sea processes, coupled with observations of cloud and precipitation structure within ETCs and ARs from other satellites, like GPM and MODIS, can help one begin to link the correlations between surface heat fluxes to changes of the mesoscale features within these synoptic-scale systems. Previous studies have shown the correlation of observed surface heat fluxes to precipitation and cloud thickness increases along the frontal regions. Still, they have only looked at the connections between ETCs and ARs when LHF and SHF were at their strongest or the peak intensity of the system, not during its early formation (or just before formation) when they may be at their strongest. 

Additionally, recent studies have examined through idealized models how surface heat fluxes within an ETC can impact the development of ETCs and ARs upstream of the primary cyclone and lead to multiple ETCs in succession, often called a family or temporal clustering of ETCs and ARs. This clustering can lead to significant and excessive precipitation over parts of the globe, such as the United States West Coast in early 2023, with successive ARs over one month. Improved observations of real-world conditions can help us better understand the interplay within these systems. This presentation will highlight the role air-sea interactions may have during the genesis and early evolution of ETCs and ARs, the correlations to cloud and precipitation structure changes, the upstream impacts, and setting the groundwork that will be able to show that air-sea interactions directly impact the development of these systems.