Dependence of precipitation extremes on temperature for different synoptic patterns in Japan

Abstract:

The empirical relationship between extreme precipitation and the corresponding temperature is expected to provide a better guide for predicting precipitation extremes in the future. The primary reason for this expectation is the fact that the moisture-holding capacity of the atmosphere increases with temperature at a rate of approximately 7% ℃^-1 according to the Clausius-Clapeyron (C-C) relation. In the mid-latitude regions, intense precipitation is strongly influenced by synoptic patterns, and a particular characteristic is long-lasting heavy precipitation driven by abundant moisture transport. However, the effect of synoptic patterns on the empirical scaling remains unclear. This study investigates the relationship between extreme precipitation and daily mean temperature using event-based precipitation dataset in Japan over a period of 25 years. We classified precipitation events into two types based on their durations: long- and short-duration events. Long-duration events refer to precipitation events lasting longer than 10 hours, sustained by atmospheric river-like circulation pattern, while short-duration events refer to those lasting less than 5 hours to consider local afternoon thunderstorms. We found that hourly and accumulated precipitation extremes considerably increase with temperature beyond the C-C rate for long-duration events. In the event peak hourly intensity, the increasing rate for long-duration event shows almost double the C-C scaling rate at relatively high temperatures and exceeds that of short-duration event. Our result suggests that synoptic-scale long-lasting precipitation events respond more to warming compared with short-duration events. This increases the risks of future widespread floods and landslides in this region.