A Statistical Study And Numerical Simulation On Short-time Heavy Rainfall In The Context Of Northeast China Cold Vortex In Liaoning Province

Based on conventional data, FNL data and hourly precipitation data in Liaoning Province in June, July and August from 2000 to 2014, short-time heavy rainfall in the context of Northeast China Cold Vortex (NCCV) is statistically studied and dynamically analyzed, with NCCV classified as north vortex, middle vortex and south vortex. In addition, the typical rainfall example caused by NCCV is analyzed with high resolution data output by WRF model.The results show that there is 755 short-time heavy rainfall which includes 227 times under the background of NCCV and heavy precipitation mainly occurs in 1 to 3 hours. Steered by middle vortex most in June, heavy rainfall is collectively affected by middle vortex and north vortex in July and August and it has a certain periodic variation. Moreover, north vortex is abundant in moisture transport while middle vortex is not so that moisture transport combined with the field of shear convergence plays an important role in severe precipitation. The precipitation near cold vortex center is likely to occur in the north of baroclinic zone and left to where upper level jet exits while rain in front of trough or behind trough is located in the south of baroclinic zone and right to where upper level jet enters, and secondary circulation resulting from upper level jet exists in precipitation area within baroclinic zone. The cyclonic circulation induced by high potential vorticity triggers ascending movement of rainfall near cold vortex center, with obvious activity of dry intrusion in the rainfall area behind trough.The typical rainfall process occurred in the developing stage of north vortex is confirmed and analyzed, and results show that the circulation background is consistent with precipitation model's, that is short-time heavy rainfall occurs in front of trough at 500 hPa , in front of shear line at 850 hPa, in the left side of the low level jet and in the cold front convergence zone. The convergence of the cold outflow sinking to the south and the warm moist southerly inflow with northerly inflow and southerly inflow in middle layer induces short-time strong rainfall, and new cold thunderstorm high is an important reason for the small increase of precipitation, and the mesoscale secondary circulation exists. In addition, the mechanism of cloud physics in different precipitation periods is obviously different in the heavy rainfall center. When the precipitation is the most strong,cold cloud precipitation plays a leading role and maximum centers of rain, graupel, snow and ice particles distribute in the same position, with the mainly melting of graupel particles. Warm cloud precipitation is more and more important with decreasing precipitation. The efficiency of cold cloud precipitation is higher than that of warm cloud precipitation so that it is easy to cause too much short-time heavy rainfall.