Numerical simulation of macro- and micro-structures of intense convective clouds with a spectral bin microphysics model

1. Introduction Spectral (bin) microphysical cloud models have been successfully used for the investigation of different microphysical processes (e. Advances in spectral bin microphysics model development have been achieved in China. For example, cloud droplets are categorized into several bins in a one-dimensional time-dependant model for warm clouds (e.g., Xiao et al., 1988a, b). The water droplet spectral distribution was formulated in a study of the evolution of the particle spectrum (e.g., Xu, 1999). A three-dimensional convective cloud model with discrete mass categories of hail/graupel has also been developed (e.g., Guo et al., 2001a, b). This model can simulate details of the growth and the distribution of hail/graupel particles, which can not be properly depicted by parameterization models. Water and ice processes and their interactions have been simulated by spectral bin microphysics in a study of the mechanisms involved in plateau precipitation systems (e.g., Zhao et al., 2004). The spectral bin microphysics of the Tel Aviv University model (e.g., Reisin et al., 1996a; Yin et al., 2000) is coupled with 3D compressible non-hydrostatic dynamics (Institute of Atmospheric Physics-IAP, China), and a real convective cloud caes is simulated Simulation results of the bin cloud model are compared with the results of the IAP 3D hailstorm numerical model (with bulk microphysics) and the observations. It was found that the bin model accurately depicts the updraft velocities and spatial structure of the reflectivity that was observed by Doppler radar. The model is suitable to study severe convection, in particular the formation and evolution mechanism of hailstorms and hail particles. 2. The cloud model 2.1 The dynamic model The dynamic framework of the model employed in this study is a three-dimensional compressible dynamic model which prognoses 3D velocity of airflows, temperature, pressure and humidity (e.g., Kong et al., 1990; Kong, 1991). The model uses a time-splitting method with a small time step to calculate the sonic wave production term to assure computational stability, while the rest of the terms are calculated using a large time step that is suitable for gravitational and meteorologically relevant waves. The model uses an Euler backward scheme to compute fields at the first time step. The model uses 36x36 grid points in the horizontal with a grid spacing of 1 km. The vertical grid contains 38 points with a grid spacing of 0.5 km. 2.2 Microphysical processes of the model The spectral bin microphysics includes a spectral description of …