The Numerical Simulation And Diagnosis Research Of Rainstorm And Severe Convection Weather In Liaoning Province

A heavy rain process occurred in Liaoning area during 29 ~ 30 July 2004 is studied in this paper. Based on synoptic maps analysises, the Hetao cyclone is regarded as the major influnce synoptic system for the heavy rain process. Through the analysis we found that Big scope south airflow and vapor transport and convergence brought by meso-scale jet, offer vapor condition which rainstorm occur and develop;Severe convergence brought by Low-level jet pulsation, and severe divergence brought by upper-level jet is directly trigger mechanism of this intense rainstorm;The severe vertical velocity is severe convection trigger to offer dynamical condition for severe convection generation in lower-troposphere.For further investigating the causes of the cyclone development, a numerical simulation by using MM5 and a diagnostic analysis based on the outputs of the model have been done. Through comparing the simulate results with the real weather, the different layers synoptic-scale circulation, height field, temperature field and precipitation were successfully re-appeared. The results showed that, potential vorticity in equity-entropy surface field, a relatively high potential vorticity area in middle-high troposphere moved, and make cyclone develop;And low-level cyclone circulation with high-level anticyclone circulation, is helpful to form low-level convergence and high-level divergence, and make the rising airflow nearby cyclone keep and strengthen.Through analysis of potential vorticity in isobaric surface field, in high-troposphere a positive potential vorticity disturbance before rainstorm generation;positive potential vorticity disturbance in high-troposphere downward, form one vertical disturbance column, now corresponding precipitation develop stage;When near ground arises negative potential vorticity disturbance, precipitation also weaken.Q vector divergence field submit piece form district of convergence and divergence, have reflected meso-scale character. In the interface of convergence district and divergence district of Q vector divergence, accompany severe convection precipitation and convection precipitation strengthen following convergence center strength, weaken following divergence center weaken.The change of the positive storm-relative helicity value has reflected the severe weak tendency of rainstorm and its system approximately. Accompanied the development of severe convection the positive storm-relative helicity value was stronger and the precipitation became more.