两类动力因子对四川盆地一次低涡暴雨的应用研究

Application Research of Two Types of Dynamical Factors in a Vortex Rainstorm in Sichuan Basin

利用常规观测资料、FY-2E卫星云顶黑体亮度温度(TBB)资料、欧洲中心0. 25°×0. 25°资料,选取质量散度、垂直螺旋度、质量垂直螺旋度、水汽垂直螺旋度、散度垂直通量、密度散度垂直通量、水汽散度通量等7个动力因子对2015年8月16-18日四川盆地一次暴雨过程进行诊断分析。结果表明:(1)此次降雨过程是由高原低涡、高原切变线、西南低涡等多个天气系统共同作用造成。(2)随着高原低值系统的东移、减弱,西南低涡的生成、发展,伴随的对流云团经历了连续生消的过程。(3)动力因子对此次暴雨过程的发展和演变有较好指示意义。动力因子大值区基本覆盖强降水区。西南低涡形成初期,动力因子大值区和高原切变线分布一致,降雨中心位于动力因子大值区和高原切变线右侧,与西南低涡中心对应。西南低涡强盛时期,动力因子大值中心、西南低涡中心、降雨中心趋于重合。降雨区上空存在质量散度辐合、气旋性涡度和水汽通量涡度的垂直向上输送及辐合上升运动。

By using the conventional observation data,the FY-2 E satellite Black Body Temperature（TBB） data,the 0.25°×0.25° data of European Center,and based on the chosen dynamical factors including mass divergence,vertical helicity,mass vertical helicity,moisture vertical helicity,divergence vertical flux,density divergence vertical flux and moisture divergence flux,diagnostic analysis was performed for a rainstorm process occurred in Sichuan Basin during 16-18 August 2015.The results showed that：（1） the rainstorm event was caused by the southwest vortex formed and maintained in the central Sichuan Basin.The southwest vortex was because of the eastward movement of plateau vortex and plateau shear lines toward Sichuan Basin.（2） Following the eastward movement and weakening of the plateau low-pressure systems（plateau vortex and plateau shear lines）,and the producing and development of the southwest vortex,the convective cloud cluster went through the process of ＂reinforce-combineweaken-regeneration-reinforce-weaken＂.（3） Dynamical factors had good indication significance for the development and evolution of the rainstorm.The high value area of the dynamical factors basically covered the strong precipitation area.At the beginning while southwest vortex formed,the distribution of the dynamical factors and the plateau shear line were the same,and the rainfall center which located at the high value area of the dynamical factors and the right side of the plateau shear line was the same as the center of the southwest vortex.At the strong stage of the southwest vortex,the high value area of the dynamical factors,the center of the southwest vortex and the rainfall center coincided.The precipitation area had profound positive vorticity column and upward movement,but the convergence layer was too shallow.The mass divergence convergence,vertical upward transportation and convergence upward movement of cyclonic vorticity and moisture flux vorticity appeared above the precipitation area.Due to the vorticity effect of the vortex-type influence system was more obvious than divergence effect,the vertical structure of three helicity-type dynamical factors including vertical helicity,mass vertical helicity and moisture vertical helicity was very significant from the lower layer to the upper layer.