High-Tide Floods and Storm Surges During Atmospheric Rivers on the US West Coast.

Christopher G Piecuch,Philip R Thompson,Sloan Coats,Thomas Wahl,Sönke Dangendorf,J T Reager,Felix W Landerer

doi:10.1029/2021gl096820

Abstract

Atmospheric rivers (ARs) cause inland hydrological impacts related to precipitation. However, little is known about coastal hazards associated with these events. We elucidate high‐tide floods (HTFs) and storm surges during ARs on the US West Coast during 1980–2016. HTFs and ARs cooccur more often than expected from chance. Between 10% and 63% of HTFs coincide with ARs on average, depending on location. However, interannual‐to‐decadal variations in HTFs are due more to tides and mean sea‐level changes than storminess variability. Only 2–15% of ARs coincide with HTFs, suggesting that ARs typically must cooccur with high tides or mean sea levels to cause HTFs. Storm surges during ARs reflect local wind, pressure, and precipitation forcing: meridional wind and barometric pressure are primary drivers, but precipitation makes secondary contributions. This study highlights the relevance of ARs to coastal impacts, clarifies the drivers of storm surge during ARs, and identifies future research directions.

Highlights

Atmospheric rivers (ARs) are long, narrow filaments of strong horizontal water vapor transport in the lower troposphere, typically associated with cold fronts of extratropical cyclones (Cordeira et al, 2013; Ralph et al, 2004; Ralph et al, 2017)
The frequency of high-tide floods (HTFs) along the US West Coast has increased in recent decades in some places (San Diego, La Jolla, San Francisco, and Seattle), and more generally shows interannual variability that correlates with phases of the El
ARs and HTFs co-occur more often than expected from random chance, and 10–63% of HTFs coincide with ARs, depending on location

Summary

Key Points:

HTFs on the US West Coast co-occur with landfalling ARs more often than expected from random chance. Between 10%–63% of HTFs observed by tide gauges coincide with landfalling ARs, depending on location. Meridional wind and barometric pressure make the main contributions to storm surge during landfalling ARs

Introduction

High-tide floods

Storm surges

Findings

Summary and Discussion