The Topograpical Enhancement Mechanism of ShortTime Heavy Rainfall in Huangshan Mountain
The spatiotemporal distribution of shorttime heavy rainfall in Huangshan Mountain region was analyzed statistically by using the observations from 191 ground automatic observation stations in Huangshan Mountain region. Statistics revealed that the frequency of shorttime severe rainfall process increases significantly from afternoon to evening (14:00-18:00) period; shorttime severe rainfall occurs most often in Huangshan Mountain and the nearby area; the distribution of shortterm heavy rainfall frequency is highly correlated with mountain shape and terrain. Using three typical cases, the function of the enhancement of mountain terrain dynamic blocking and thermodynamics in shorttime severe rainfall is analyzed. The findings are concluded as follows: (1) The rainfall increases due to the lifting rate of mountain terrain on the windward slope, and the rainfall coulds reach 60% according to the diagnosis by the water vapor budget method. (2) When the frontal surface passes the mountain area, its vertical disturbance enhances frontogenesis, while in the leeward slope, the surface vortex, and ascending motion are enhanced, resulting in the increase in precipitation. (3) In the southwest region thermal low forms due to the difference of surface latent heat flux, making this area warmer and wetter and the atmospheric instability enhanced. Affected by cold advection, severe convective weather develops, thus increasing the precipitation in the mountain region.