Comparative Analysis of Five Transverse Shear Rainstorms During the Year 2009 in Shanxi
With conventional and unconventional meteorological observational data, aiming at the 5 transverse shear regional rainstorm weather processes appearing in the flood season during 2009 in Shanxi area, the authors configured the flow pattern, diagnosed the physical variables, and comprehensively analyzed the satellite, radar, and the GPS/MET data and the predictability, and discovered that within the 5 transverse shear rainstorm processes, the rainstorm process appearing during July 7-8, 2009, was the one that the range was the widest, the precipitation strength was the strongest, and the system configuration was the most complete; in the continuous rainy process, whether rainstorm days or nonstorm days, all have the following features that humidity was high and thick, and this was the biggest difference from the other 4 noncontinuous rainy rainstorm processes; the convective or mixed rainstorm, has characteristics that it would decrease with the increasing height under 500 hPa, and would increase with the increasing height above 500 hPa 12 h ahead of the rainstorm setting in. Moreover the stable rainstorm has characteristics that it would increase with the increasing height. The 500 hPa horse latitude highs were all zonal types in the 5 rainstorm processes, and the 700 hPa horse latitude highs all had the southwest axis of jet stream being combined and the continental small high being accompanied, the rainstorm falling areas were all located at the area between the big value zone of the air column total vapor gradient and its southern (eastern), within 0.5°E (N). The analysis result shows that: the location difference of the small high led to the convergence of the different wind direction and the generation of transverse shear line in different trend, the latitude difference of the jet stream head stretching toward north led to the latitude difference of transverse shear line location, which would directly influence the falling areas of rainstorms; the strength difference of low vortex made the evident difference of precipitation; the more complete the highlow air system configuration is, the stronger will be the predictability of rainstorm falling area and magnitude; during the continuous rainy processes, the vertical speed, moisture flux divergence, and vertical wind shear are the sensitive factors in judging whether rainstorm will approach or not 24 h in advance. The vapor front area trend is almost consistent with the midlow layer shear line; before the rain approaches, the stable rainstorm process has more initial lead time in relation to the formation of the vapor front area than the severe convective rainstorm process, moreover, the stronger the convection is, the later the vapor front area forms.