High-Resolution Simulations of High-Impact Weather Systems Using the Cloud-Resolving Model on the Earth Simulator

Summary

High-impact weather systems occasionally cause huge disasters to human society owing to heavy rainfall and/or violent wind. They consist of cumulonimbus clouds and usually have a multiscale structure. High-resolution simulations within a large domain are necessary for quantitatively accurate prediction of the weather systems and prevention/reduction of disasters. For the simulations, we have been developing a cloud-resolving model named the Cloud Resolving Storm Simulator (CReSS). The model is designed for a parallel computer and was optimized for the Earth Simulator in the present study. The purpose of the present research is highresolution simulations of high-impact weather systems in a large calculation domain with resolving individual cumulonimbus clouds using the CReSS model on the Earth Simulator. Characteristic high-impact weather systems in East Asia are the Baiu front, typhoons, and winter snowstorms. The present chapter describes simulations of these significant weather systems. We have chosen for the case study of the Baiu front the Niigata—Fukushima heavy rainfall event on July 13, 2004. Typhoons for simulations are T0418, which caused a huge disaster due to strong wind, and T0423, which caused severe flood over the western Japan in 2004. Snowstorms were studied by an idealized numerical experiment as well as by a simulation of cold air outbreak over the Sea of Japan. These experiments clarified both the overall structures of weather systems and individual clouds. The high-resolution simulations resolving individual clouds permit a more quantitative prediction of precipitation. They contribute to accurate prediction of wind and precipitation and to reduction of disasters caused by high-impact weather systems.