Impact of Sea Surface Temperature near Japan on the Extra-Tropical Cyclone Induced Heavy Snowfall in Tokyo by a Regional Atmospheric Model

Abstract

This study investigated the impact of sea surface temperature (SST) on a snowfall event of late January 2018 on Kanto, Honshu, Japan, associated with an extratropical cyclone (south-coast cyclone) along the Pacific side, during the Kuroshio large meandering period by a regional atmospheric model. We addressed SST impacts on the snowfall event under almost the same synoptic-scale conditions, such as extratropical cyclone, in a framework of lateral boundary forcing. We conducted control experiments (KLM) with SST of the Kuroshio large meandering, and sensitivity experiments (NKLM) prescribed non-Kuroshio large meandering SSTs. Observational results showed that SST anomalies south of Tokai, and east of northern Kanto and Tohoku could be candidates to modify a snowfall event. As simulated results, timings of snowfall and precipitation associated with the extratropical cyclone was reproduced. Unlike what has been suggested, the SST impact south of Tokai on snowfall was not clear. However, the SST east of northern Kanto and Tohoku showed a significant impact. This impact was explained by southward advection of modified air-mass from east of northern Kanto and Tohoku. Additional sensitivity experiments supported this result. This study implies the importance of the SST anomaly east of northern Kanto and Tohoku for snowfall in Tokyo.