Impact of SST on Present and Future Extreme Precipitation in Hokkaido Investigated Considering Weather Patterns

Abstract

AbstractThis study investigated the impact of sea surface temperature (SST) on extreme precipitation events in North Japan and its relation to synoptic weather patterns using large‐ensemble climate simulations. Eight weather patterns were identified by applying cluster analysis to sea level pressure anomalies for selected days with extreme precipitation derived from a 3000‐year historical climate experiment. Interannual variability of extreme precipitation days associated with two specific weather patterns, characterized by a weak low‐pressure system and an atmospheric river (AR), significantly correlated with that of SST over the Sea of Japan, with a correlation coefficient of 0.37 and 0.53, respectively. In higher SST years, the increased atmospheric moisture can increase the extreme precipitation in the inland area of Hokkaido for the weather pattern associated with a weak low‐pressure system, whereas it appears to enhance orographic precipitation along the western slopes of mountains for the pattern resembling AR. These results indicate that the effect of local SST on extreme precipitation strongly depends on the weather patterns. In the future projection, the two weather patterns that are sensitive to SST over the Sea of Japan show a sharp increase of more than 4 times under the 4 K warming climate. Moreover, the magnitude of extreme precipitation was also found to increase with SST, broadly following the Clausius–Clapeyron relation in both historical and warmed climates. These results suggest increased risk of heavy precipitation associated with such weather patterns over North Japan in the future.