The Role of Air–Sea Interactions in Atmospheric Rivers: Case Studies Using the SKRIPS Regional Coupled Model

Rui Sun,Hyodae Seo,Matthew R Mazloff,Arthur J Miller,Ibrahim Hoteit,Aneesh C Subramanian,Bruce D Cornuelle,F Martin Ralph

doi:10.1029/2020jd032885

Abstract

AbstractAtmospheric rivers (ARs) play a key role in California's water supply and are responsible for most of the extreme precipitation and major flooding along the west coast of North America. Given the high societal impact, it is critical to improve our understanding and prediction of ARs. This study uses a regional coupled ocean–atmosphere modeling system to make hindcasts of ARs up to 14 days. Two groups of coupled runs are highlighted in the comparison: (1) ARs occurring during times with strong sea surface temperature (SST) cooling and (2) ARs occurring during times with weak SST cooling. During the events with strong SST cooling, the coupled model simulates strong upward air–sea heat fluxes associated with ARs; on the other hand, when the SST cooling is weak, the coupled model simulates downward air–sea heat fluxes in the AR region. Validation data shows that the coupled model skillfully reproduces the evolving SST, as well as the surface turbulent heat transfers between the ocean and atmosphere. The roles of air–sea interactions in AR events are investigated by comparing coupled model hindcasts to hindcasts made using persistent SST. To evaluate the influence of the ocean on ARs we analyze two representative variables of AR intensity, the vertically integrated water vapor (IWV) and integrated vapor transport (IVT). During strong SST cooling AR events the simulated IWV is improved by about 12% in the coupled run at lead times greater than one week. For IVT, which is about twice more variable, the improvement in the coupled run is about 5%.

Highlights

Atmospheric rivers (ARs) are narrow, elongated plumes of enhanced water vapor transport over the oceans that can extend from the tropics and subtropics into the extratropics (Bao et al, 2006; Jankov et al, 2009; Ralph et al, 2004, 2005, 2018)
We found that the sea surface temperature (SST) cooling in different cases can be significantly different, we highlighted two groups of simulations: (1) strong cooling ARs and (2) weak cooling ARs
The strong cooling group had the 31 AR events that occurred with the most significant SST cooling and the weak cooling group had the 31 AR events that occurred with the weakest cooling

Summary

Introduction

Atmospheric rivers (ARs) are narrow, elongated plumes of enhanced water vapor transport over the oceans that can extend from the tropics and subtropics into the extratropics (Bao et al, 2006; Jankov et al, 2009; Ralph et al, 2004, 2005, 2018). ARs can have both beneficial (e.g., replenishing water reservoirs) and detrimental (e.g., causing destructive floods and landslides) impacts on regional economies and public safety (Corringham et al, 2019; DeFlorio et al, 2018; Ralph et al, 2019).

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