Projected regional-scale changes in atmospheric stability condition for the development of summertime convective precipitation in the Tokyo metropolitan area under global warming

摘要

This study examined regional-scale changes in stability conditions for the occurrence of summertime convective precipitation under global warming projected by global climate simulations. Precipitation events over the Kanto Plain on synoptically undisturbed days were specifically focused on. The outputs of the 20-km-resolution global model simulations for the present and a future warming climate were used for the analyses. It was shown that temperature and moisture content throughout the troposphere are projected to increase more in the rainy cases than in the August mean cases from the present climate to the future and that the moisture increase below the 700-hPa level is significantly enhanced. The effects of future warming result in the moisture increase favorably at the lower levels. Owing to the low-level moisture increase, some stability indices indicate a destabilizing tendency with a statistical significance. From the projected changes in the stability condition for precipitation occurrence, it is implied that the precipitation amount is considered to increase if a cumulonimbus cloud and its organized systems once develop. The degree of the destabilization of precipitation environments is projected to increase more significantly than that of non-precipitation environments, and therefore, the precipitation will be more intensified in a future climate.