Abstract:
Using the NCEP 1 °×1 ° data,encrypted automatic stations data of Sichuan Province and FY2C infrared cloud image data,characteristics of satellite cloud pictures for four similar MCC process on July 6-9,2012 and July 4—6,2011 occurred in the Sichuan Basin which caused heavy rain were analyzed.On this basis,atmospheric circulation characteristics of the creation and development of MCC had been discussed and the moisture,heat and power mechanism on the development process of MCC had been further studied by diagnostic methods (vertical divergence flux,dry potential vorticity).The results showed that during the two cases,the first and third MCC generated and developed in the convective clouds for cirrus plume in the basin,the second and forth MCC generated ,developed and merged in the remaining structures convective clouds,all performed bright temperature decrease,area increases,and surrounding structures would gradually diminish on the plateau of Western Sichuan and MCS in the forming process.Strong and sustained water vapor transport from the bay of Bengal and instability stratification conditions,low-level troposphere for southwest vortex area uplift caused strong vertical divergence flux convergence upward transportation and high-level divergence was corresponding to the dynamic mechanism for MCC development and continuous,850hPa vertical divergence flux convergence zone had good corresponding relationship of time and space with MCC area and observation of ground rain fall area.High value potential vorticity from high latitude extend to the south and low latitude,low value from low-level had the characteristics of upward spread north.when the dry cold air intersected with warm moist air,850hPa strong wind shear and the convergent in the southwest vortex area of the left side before the jet resulted strong upward movement,triggered the release of convection instability energy,inspired MCC cloud and caused heavy rain.