Analysis Of The Cause And Structure Of Multiple Convective Zones Of A Jiang-huai Cyclone's Warm Front

This paper simulated a heavy rainfall case caused by Jiang-Huai cyclone that occurred in south Anhui province from 12:00 July 4 to 06:00 July 5 2014. From the large scale circulation background, moisture condition and the structure and evolution of radar echo, simulated results on warm front are consistent with the observed, and used to investigate multiple convective rain belts' structure and the reason for appearing near the warm front.The results indicate that the little convections are all under 300hPa both in simulated and observed situation, lasting around 2-3 hours, with 100 km long at most and 10 km wide around. Between bands, their spacings are about 50-100 km,and all of them are tilting east-southern with height. Do the profile perpendicular to the warm, each of little convective bands has similar circulation characteristic: on east of the convective region corresponding warm rising air distributed from its low-level to high-level; upper western convective zone are controlled by cold area;and close to the ground, there is a similar cold pool, updraft south of the convective belts is favor of convections' back building and forming belted structures. On the single convective rain belts, there is the area of 0<Ri<1 at 800hPa near warm front,with the area of EPV<0 contributing. In stable stratification, the wind field distributed in roller shape, with the structure characteristics of the existence of gravitational waves. There is convective instability at 600-700hPa, generating multiple convective bands, and between convective belts, there is the area of EPV>0.It can be concluded that warm rising air in conditional symmetric unstable condition around 800hPa triggered conditional symmetric instability and gravity waves, and convective instability above 700hPa. This implies that, the causes of little convective rain belts' formation is mainly for symmetric-convective instability.Using Q vector in the warm front to diagnose secondary circulation,frontogenesis and precipitation of little rain belts, it can be found that the overlapping area of the water vapor flux convergence and Q vector divergence'convergence at 700hPa, would be the downstream of precipitation, combined with the direction of the secondary circulation, and dragged by the sinking air. The other sides, quantitative analyzing its frontogenesis mechanism by frontogenesis function,it is as same as its in the cold front, and is decided by the heeling item, further analysis each value of the heeling item, we can confirm that vertical wind speed shear is the main reason of frontogenesis, caused mainly by rising adiabatic heating,and sinking adiabatic cooling, increasing the temperature level gradient.