Analysis on Characteristics of Mesoscale Convective System during a Short-term Rainstorm Process in North of Ningxia

By using the data of automatic weather station,lightning location system,Doppler radar and satellite,the short-term rainstorm process occurred at Shitanjing on 18 July 2008 is analyzed.Result shows that the short-term rainstorm occurred under the circulation of ridge at west and trough at east,and was affected by the transversal trough at the back of northeast cold vortex and the low pressure system.There are two strong convective cells,which influenced Shitanjing successively,and then combined and sustained.The MCS(mesoscale convective system) maintained in the north of Ningxia for almost 6 hours,and the highest cloud top TBB(blackbody brightness temperature) gradient located at Shitanjing.Corresponding with the three precipitation stages,there are three peaks of echo intensity,echo tops and VIL during the rainstorm process.There are cyclonic convergence and adverse wind area in radial velocity graphs.The appearing of adverse wind area is 20—30 minutes earlier than that of the strong precipitation,and its echo evolution has better relationship with the evolution of precipitation.The high density lightning area locates in the front of precipitation center,and the sudden increasing of lightning frequency occurs one hour earlier than the heavy rain.