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

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 precipitation cases are classified into three types: (1) subtropical high edge pattern (PatternⅠ), (2) low-trough pattern (PatternⅡ) and (3) typhoon inverted 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 system 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 vorticity 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 of θse with strong transportation of warm and wet air in the mid- and low-level and deep wet areas. High zero-temperature 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.