Analysis on the difference between typical and non-typical Meiyu front rainstorms in 2011 over Jiangsu province

 In the year of 2011, the Meiyu Period in Jiangsu province is divided into two stages: typical Meiyu front rainstorm and non-typical Meiyu front rainstorm. Using synthesis average method, routine data and NCEP/NCAR reanalysis data the differences and similarities in weather situation, thermal feathers and dynamic characteristics between the two stages were analyzed. The result shows that the typical Meiyu front rainstorm was caused by the trough at 500 hPa and over mid-latitude together with subtropical high, and the rainstorm regions were around the 5840 gpm line. The shear line was in low troposphere, and Meiyu front was obviously characterized near surface level. The disturbance of meridional wind was deep north wind, and moist warm air came from the Bay of Bengal and the middle-north part of the South China Sea. In the mid-high level the southwest air flow in front of deep trough with synoptic scale was over Jiangsu in the non-typical stage, and cold air came from the back of the northeast cold vortex, and there was the convergence line with inverted trough in the low-level. Besides, the intensity of frontal zone near surface was weaker. The abnormal and strong moist warm air came from the east part of the South China Sea to the north passing through the Taiwan Strait and the East China Sea. The disturbance of meridional wind in low troposphere was south wind and north wind in mid- and high-level, and rainstorm occurred in the convergence zone of wind velocity of low-level south wind. The distribution of the two types of heavy rainstorm was in the warm side of frontal zone, the northern side of great value ofθseand q and strong motion region.