Numerical simulations with the Advanced Regional Prediction System(ARPS) model were performed to investigate the impact of microphysical drop size distribution(DSD) on tornadogenesis in a subtropical supercell thunderstorm over Anhui Province, eastern China. Sensitivity experiments with different intercept parameters of rain, hail and snow DSDs in a Lin-type microphysics scheme were conducted. Results showed that rain and hail DSDs have a significant impact on the simulated storm both microphysically and dynamically. DSDs characterized by larger(smaller) intercepts have a smaller(larger) particle size and a lower(higher) mass-weighted mean fall velocity, and produce relatively stronger(weaker) and wider(narrower)cold pools through enhanced(reduced) rain evaporation and hail melting processes, which are then less favorable(favorable)for tornadogenesis. However, tornadogenesis will also be suppressed by the weakened mid-level mesocyclone when the cold pool is too weak. When compared to a U.S. Great Plain case, the two microphysical processes are more sensitive to DSD variations in the present case with a higher melting level and deeper warm layer. This suggests that DSD-related cloud microphysics has a stronger influence on tornadogenesis in supercells over the subtropics than the U.S. Great Plains.
展开▼
