A three‐dimensional numerical model of cloud dynamics, microphysics, and chemistry: 2. A case study of the dynamics and microphysics of a severe local storm

Abstract

A strong convective storm has been modeled by using our three‐dimensional cloud model (Wang and Chang, this issue). The maximum updraft is about 30 m/s and the maximum Ze is 72.3 dBZ. The modeled precipitation feature and three‐dimensional radar reflectivity factors are closed to the observed data. The whole life cycle of this modeled storm can be divided into three stages: the “explosive growth” stage (∼10 ‐ 24 min of model time), the mature stage (∼24 ‐ 55 min of model time), and the static stage (after 55 min of model time). Almost all precipitated water categories grew fast during the explosive growth stage. The latent heat release during this stage produced strong updraft. In the mature stage, precipitation inside the cloud gradually changed from liquid‐phase to ice‐phase. Both graupels and hailstones initially formed around 10 km in height and inside the initial cell. Only in the later stages were they transported or fallen to other regions. Some new cores of hail were found in other regions. In the static stage, precipitation weakened. Ice crystals formed rapidly when the plume of the storm spread at the higher level. These crystals then fell into the lower levels of the storm. The modeled storm possessed a cyclonically‐rotating updraft. The inflow air of the storm came from different regions of the model domain. A short (less than 20 min) heavy precipitation period appeared during the simulation. Most of the precipitation came from ice‐phase particles, primarily the graupels and hailstones. The maximum precipitation rate occurring in a single grid point was about 989 mm/hr, while the domain‐averaged rate was about 3 mm/hr. Heavy precipitation and the downdraft also produced one high‐temperature region and two low‐temperature regions near the surface.