Analysis Of Warm-sector Rainstorms Characteristics Over The Middle-lower Reaches Of The Yangtze River Valley

By analyzing the NCEP 1°×1°6-hourly reanalysis data and conventional and non-conventional observation data from May to September during 2007 and 2013, the warm-sector rainstorms over the middle-lower reaches of the Yangtze River valley are studied. The warm-sector rainstorms in this area can be divided into three types based on the weather situation, which are cold-front, warm shear-line and subtropical high inside. Statistical results show that the warm-sector rainstorms occurs generally in the warm sector,100-300Km away from the shear-line at 850hPa (cold front on the ground). The significant characteristics obtained from the research are:(1) the cold-front type often occurs on May and June, with a weak intensity and uniform distribution. The warm shear-line type usually occurs in the south part of this area with high frequency and strong intensity, mainly on June and July. The precipitation inside subtropical high occur least with most strong intensity often on July and August. The orographic action of the Dabie and Wannan mountains provide advantage condition for local large heavy rain. (2) Short-time strong rainfall make great contributions to the rainstorm, and the heavier the rainstorm, the greater proportion of short-time strong rainfall accounted for. (3) The warm-sector rainstorms under the background of cold front generally happen in the prefrontal trough, the rainfall areas have close contact with the place of the coupling of upper and low-level jet. In the second type, the rainstorms have high correlation with the structure of mesoscale jet and topographic forcing under the background of warm shear-line in the lower level stationary front on the ground and abundant water vapor. And the heavy rainfall happen inside the subtropical high have close relationship with accumulation of water vapor and the development of convective instability condition. Three kinds conceptual model have been built based on these above. A ca se of warm-sector rainstorm during 9-10 June 2008 is simulated using mesocale model WRF, the precipitation are basically the same as actual situation, and the model results are in accordance with the conceptual model built before.