中尺度天气图分析技术在2011年我国南方4次强降水过程中的应用

对12 h 50 mm以上的强降水带的预报,模式输出的降水资料是预报的重要依据,但是有时偏差可达100～200 km.本文尝试依据国家气象中心2010年下发的《中尺度天气图分析技术规范(暂行稿)》,利用探空资料,对2011年6月我国南方梅雨期间强降水过程中4次12 h最强降水时段的环境场进行中尺度天气图分析,得到了有利于梅雨锋附近的强降水的预报着眼点,给出了判断强降水落区的一些参考依据.700 hPa以下西南(偏南)急流汇合区,在这些地区,具备了较强的动力、水汽辐合和一定的风垂直切变.地面气压槽中低于日变化的3h变压低值区(中心)易形成变压风辐合流场,也是强降水易发区(中心).多数情况下锋面可以作为强降水南界,但当925 hPa暖切变位于地面锋面南侧(附近),强降水发生在锋前暖区,10 m·s-1以上西南急流所能到达的纬度可作为南界.500 hPa槽前≥18 m·s-1中层西南急流轴一般可作为50 mm以上的强降水区域的北界,但当925 hPa切变位置与中层西南急流位置重叠或位于其北侧时,则以700 hPa切变为北边界.将这些判据应用于多次强降水天气时段中,并与日本模式输出降水比较,在强雨带南北界以及降水中心方面有订正作用.中尺度天气图分析技术及预报思路是订正模式对强降水落区预报的有效手段之一.

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.