淮河上游短时强降水天气学分型与物理诊断量阈值初探

Tentative discussion on synoptic type and physical diagnostic threshold of short-time strong precipitation in upper reaches of the Huaihe River

利用常规高空、地面气象观测资料和NCEP 1°×1°再分析资料,对2001—2010年淮河上游短时强降水过程进行中尺度天气分析和物理量场诊断。然后,根据该区域短时强降水的环流形势和主要影响系统,将短时强降水过程分为副高边缘型、低槽型和台风倒槽型,其中副高边缘型又分为副高和低槽共同影响型、副高控制型和下滑槽副高型,归纳各类短时强降水天气系统配置模型,并提炼出表征短时强降水天气的物理量阈值。结果表明,淮河上游77.8%的短时强降水与西太平洋副热带高压有关,中低层多有急流、切变线和低涡,地面影响系统多为倒槽、辐合线和弱冷锋。短时强降水发生在低层辐合、高层辐散、低层正涡度以及中层上升运动的动力条件下;中低层有较强暖湿空气输送,湿区深厚,强降水发生在假相当位温(θse)大值区顶部;0℃层高度较高,中层风切变小,低层风切变较大,有利于短时强降水发生。

Mesoscale weather analysis and physical diagnostics for the short-time strong precipitation cases in upper reaches of the Huaihe River from 2001 to 2010 are performed using routine upper-air and surface observations and 1 °×1 ° resolution NCEP reanalysis data. Based on the circulation situation and main influential systems of the short-term strong precipitation in this reaches, the short-term strong precipita-tion cases are classified into three types：（1） subtropical high edge pattern （PatternⅠ）, （2） low-trough pattern （PatternⅡ） and （3） typhoon in-verted trough pattern （PatternⅢ）. In addition, PatternⅠis further classified into three sub-patterns, namely consociation of subtropical high and low trough, subtropical high-controlled, and declined trough in the edge of subtropical high. Analyzing all types of the configuration sys-tem models of the short time strong precipitation, the physical thresholds that characterize the short-term strong precipitation are established. The results indicate that 77.8%of the short-time strong precipitation cases in upper reaches of the Huaihe River are related to subtropical high over the west Pacific;there are jet stream, shear line and vortex in the mid-and low-level, and inverted trough, convergence line and weak cold front in ground level. The short-time strong precipitation occurred under the dynamic conditions of convergence and positive vortic-ity advection in the low-level, divergence in the upper level and ascending movement in the medium level. Heavy precipitation occurs at the top of the large value area ofθse with strong transportation of warm and wet air in the mid-and low-level and deep wet areas. High zero-tem-perature level, weak wind shear in the mid-level and strong wind shear in the low-level are factors in favor of the occurrence of the short-time heavy precipitation.