Application of Mesoscale Synoptic Analysis Techniques in Four Heavy Rainfall Processes in South China in 2011
The precipitation data from model is a significant forecast basis for the severe precipitation of more than 50 mm in 12 h, but sometimes the deviation can be 100-200 km in forecasting. Based on Mesoscale Synoptic Analysis Technics Regulation (provisional) and sounding data this paper tries to analyze the mesoscale weather chart of 4 severe rainfall processes in South China during the Meiyu season of 2011, getting the key point of forecasting the heavy rainfall near Meiyu front and presenting some evidences for estimating the precipitation regions. Convergence zones of southwest or southern jet under 700 hPa have strong power, moisture convergence and certain vertical wind shear. Surface pressure trough lower than the minimum of 3 h daily variation is prone to form convergence flow field of isallobaric wind. And it is also the heavy rainfall areas (center). In most circumstances, the front can be regarded as southern boundary of the heavy rainfall, but when the 925 hPa warm shear is in (or near) the south of surface front, heavy rainfall occurs in the warm sector ahead of fronts. And, southwest jet above 10 m·s-1which reaches the latitude areas can act as the southern boundary. More than 18 ·s -1 southwest jet in front of trough at 500 hPa can act as the northern boundary of the heavy rainfall area. When the position of 925 hPa shear line overlaps the southwest jet or in the north of it, the 700 hPa shear line can be regarded as the northern boundary. Comparing these criterions with the output of Japanese model, it is found that the results can rectify the southern and northern boundaries of strong rainfall belt as well as rainfall center. Therefore, mesoscale Synoptic Analysis Technics and its forecasting ideas is an effective means for the revised model of heavy rain location forecasting.