Numerical Sensitivity Study of Rainband Precipitation and Evolution

Name: Tsutomu Takahashi & Tetsuya Kawano

@The evolution of rain and the precipitation process producing it have been examined in a deep, two dimensional, rainband model with a fixed environment and varying microphysical processes. The evolution of rain, the activity of the rainband cells, and the pattern of heat release were all seen to differ with differing processes.

@In the models with maritime microphysics, rain occured in the early stages, in both the forward cell and the cell in the rear. Subsequently, rain was produced between these cells, forming a broad rainband. Heat was released nearly uniformly throughout the cloud above the freezing level and there were strong, horizontal winds near that level. The updraft was enhanced during the intermittent development of new cells. In the models using continental microphysics, only weak rain occured in the leading cells and was heavier in the cells at the rear. Although new rain also occurred in the middle of the band, the most intense and continuous rain was produced at the rear. In these cases, heat was released in a narrow area above the freezing level and during successive cell development, strong updrafts occurred in the rear cell.

@In cases without ice nuclei, the clouds were shallow and most of the rain was produced in the forward cells. The cases with ice nuclei and freezing produced nearly equal amounts of rain in both the front and rear cells.

@It is concluded that, in addition to stability and shear, the precipitation process is also important in the determination of rainband characteristics.