BLOCKING EFFECT OF HIGH PRESSURE SYSTEM ON THE FORMATION OF EXTRA-INTENSE HEAVY RAIN

Commonly the centre of intense heavy rain is occurred in a very limited area,but for the three extra-intense heavy rains of present study,63-8 in N.China,75-8 in C.China and 77-8 in the desert region of Inner Mongolia,which are all appeared under the environments of "Western Low and Eastern Blocking" (E.B.) pattern.1) It affects the precipitation systems stagging in a local place and/or changes the trajectories of low vortices and urges them into the same raining areas intermittently.And when the low vortex was retreated,the heaviest rainfall appeared.2) Transports water vapour into raining area in a quite thicker air column than that of low level jet.And also the air flows by the west side of E.B.produce strong cycIonic vorticity frequently,that transForts water vapour and forms meso-scale precipitation systems more favorable than that of the low level jets.3) Air flows behind E.B,conjugated with the adequate topographic relief,that enchances the precipitation and makes the raining areas overlapped.Such that extra-intense heavy rains could be occurred in higher latitudes of semiarid areas,and occasionlly even in desert region of N.China.Such extra-intense heavy rains could not be explained by static local humidity and temperature only.This is also a principal discrimination between the prolonged extra-intense heavy rain and the short-range convective precipitation and/or the common precipitations.