Surface Process and Topographic Effect on the Weather Development in Kanto Region

A land surface model is developed to model the interaction between urban surface and atmosphere, which includes the radiation, aerodynamic transfer and soil sub-models. The model couples with a 3-D non-hydrostatic, numerical weather prediction system to investigate the weather patterns in Kanto region, Japan. The first study finds that the thermal response to surface discontinuity in Kanto results in quite strong sea-breeze in daytime and favorable to the formation of rainfall, but very weak land-breeze at night. The second study is to investigate the mechanism of heavy precipitation using one-way nesting method. The study reveals that the topography in this region plays a very important role in producing local heavy precipitation. When southerly and easterly wind approaches to the mountains at the north and west of Kanto Plain, the mountains divert the flow and cause face-to-face conflict at the narrow interface between the mountains and plain, which is an effective way to drive upward airflow. If the updraft air is warm and moist, and happens to encounter cold advection in upper layer, then water vapor condenses dramatically and heavy rainfall band forms at the narrow interface.