High‐Tide Floods and Storm Surges During Atmospheric Rivers on the US West Coast. Issue 2 (25th January 2022)

• Record Type: Journal Article
• Authors: Piecuch, Christopher G.; Coats, Sloan; Dangendorf, Sönke; Landerer, Felix W.; Reager, J. T.; Thompson, Philip R.; Wahl, Thomas
• Is Part Of: Geophysical research letters. Volume 49:Issue 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-25
• Subjects: atmospheric rivers -- high‐tide flooding -- storm surge -- coastal impacts -- coastal hazards -- sea level; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL096820
• Languages: English
• ISSNs: 0094-8276

Abstract

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. Plain Language Summary: ARs drive hydrological hazards over land related to extreme precipitation. As they make landfall, ARs typically bring heavy rains, strong winds, and low pressures to the coast. While these factors can cause storm surge and coastal flooding, little attention has been paid to possible coastal impacts of ARs. We establish relationships between ARs and HTFs on the US West Coast and identify the factors causing storm surge during ARs. HTFs occur at nearly the same time that ARs make landfall more often than expected from chance, suggesting that ARs contribute importantly to HTFs. Even so, few ARs lead to HTFs—favorable tides or mean sea‐level anomalies are usually needed on top of the storm surge from an AR to cause a HTF. Storm surge during an AR can be explained by the heavy rain, strong wind, and low pressure typically associated with the event; wind and pressure are the primary factors causing the surge, but rainfall can also have a secondary influence. Our results highlight that HTFs arise from the subtle interweaving of storm surge, tide, and mean sea‐level effects, thus providing important information to managers and modelers, and motivating future studies on relationships between ARs and coastal hazards globally. Key Points: HTFs on the US West Coast cooccur with landfalling ARs more often than expected from random chance Between 10% and 63% of HTFs observed by tide gauges coincide with landfalling ARs, depending on location Meridional wind and barometric pressure make primary contributions to storm surge during ARs, but rainfall can also have a secondary effect