The effect of land surface state on heat thunderstorms in Japan

Kazuyoshi Souma, IPRC

ABSTRACT

In recent times, frequent thunderbolts and floods in big cities have been caused by heat thunderstorms in summer season in Japan. Although the heating from land surface is very important for the forecast of heat thunderstorms, land surface processes are treated very simply in short term weather prediction in Japan. Therefore, improving the land surface processes can be an effective solution for better short term prediction.

In this study, an estimation method of the spatial distribution of the land surface state is developed to initialize short term weather prediction. The effect of soil moisture distribution on a heat thunderstorm in summer season is discussed using cloud resolving atmosphere-land coupled model. The rainfall amount over plain was decreased in simulation considering homogenously wet soil moisture than that considering realistic distribution. It was also indicated that distribution of the realistic initial soil moisture can improve the prediction accuracy of the summertime heat thunderstorm in Japan. Additionally, the impact of urban environment (especially anthropogenic heat) on a heavy rainfall event over Tokyo is also discussed. It was found that changes of urban environment affected the positions and amounts of rainfall.