Mesoscale Analysis of a Heavy Rainstorm in Yulin City of Northern Shaanxi

[Objective]The study aims at analyzing a regional rainstorm in Yulin City of northern Shaanxi.[Method]Based on conventional meteorological data,satellite cloud pictures and ncep 1°× 1° reanalysis products,a regional rainstorm occurring during July 1-3,2011 in Yulin City of northern Shaanxi was discussed from the aspects of circulation pattern,mesoscale system,water vapor and dynamical conditions.[Result]There was a small closed high-pressure center near Fujian,around which southwest air flow existed constantly,providing water vapor for rainstorm areas for a long time;plateau trough moved eastwards,which provided dynamical field for rainstorm areas;the convergence between northeast cold air and low-level jet flow triggered this rainstorm;rainstorm areas were closely related to mesoscale low-pressure,and the storm appeared in the lowlevel jet flow in front of mesoscale low pressure;upper-trough cloud system and low-level jet cloud system combined,increased and generated rainstorm cloud cluster,while brightness temperature on the top of clouds was below-90 ℃.[Conclusion] The research could provide theoretical foundation for forecast of rainstorms in future.