Sensitivity of Midlatitude Heavy Precipitation to SST: A Case Study in the Sea of Japan Area on 9 August 2013

Abstract

This study investigates the influence of sea surface temperature (SST) over the Sea of Japan on a heavy precipitation event that occurred over the northern part (Northern Tohoku region) of Japan's largest island on 9 August 2013. Sensitivity experiments with the Weather Research and Forecasting model show that warmer (cooler) SSTs prescribed over the Sea of Japan in the simulations lead to an increase (decrease) in 24-hr precipitation averaged within the Northern Tohoku region, especially on the Sea of Japan (i.e., windward) side. Though no significant relationship is found between the local maxima and SSTs over the Sea of Japan, those SST values over the Sea of Japan affect the evolution of the intense convective precipitation; higher (lower) SSTs act to shift the location of intense precipitation on the upwind (downwind) side in the present event. The different evolution results in a different interaction with the downstream orography, leading to no significant relationship between the local maxima of intense precipitation and SSTs. The differences arise from the sensitivity of convective updraft to SSTs. The simulations thus suggest that uncertainties in currently available SST products may alter both the area-averaged precipitation and the geographical locations of intense precipitation, which can potentially impact flash flood and landslide warnings.