Atmospheric rivers (ARs) are responsible for over 90% of poleward water vapor transport in the mid-latitudes and can produce extreme precipitation when making landfall. This study demonstrates, using high-resolution climate models and observations, that mesoscale sea-surface temperature (SST) anomalies along the Kuroshio Extension can remotely influence landfalling ARs and related heavy precipitation along the west coast of North America. Including mesoscale SST forcing increases landfalling ARs by approximately 40% and heavy precipitation in mountainous regions by up to 30%. The asymmetrical atmospheric response to warm vs. cold mesoscale SSTs is proposed as the forcing mechanism, increasing moisture flux above the planetary boundary layer and enhancing AR genesis.

Xue Liu, Xiaohui Ma, Ping Chang, Yinglai Jia, Dan Fu, Guangzhi Xu, Lixin Wu, R. Saravanan, Christina M. Patricola