STRUCTURE OF MESO β AND γ SCALE ON MEIYU IN HUAIHE RIVER BASIN ON 30 JUNE,2003 BY DUALDOPPLER RADAR

The heavy rainfall existed for a long time in the Yangtze-Huaihe river basin on 2003 Meiyu. A heavy rain occurred in the dual-Doppler coverage, up to 159 mm rainfall in Wuhu and 146 mm in Wuwei from 08:00 on June 29 to 08:00 on June 30.The three-dimensional wind of the heavy rain were retrieved by MUSCAT (multiple Doppler synthesis and continuity adjustment technique) using the dualDoppler radar volume scan data which located in Hefei and Maanshan city. The three-dimensional kinematic structure of this rain were analyzed based on the 3-D wind. It showed that this heavy rainfall in the Meiyu front were caused by meso-β-scale convergence line and mesoγ scale vortices which mixed in the convergence line at the low level. These convergence line and vortices were the important mechanism for the broken and maintenance of the rain. The 3-D structure of the heavy rain has some difference in the early and later period.In the early part of the heavy rainfall period, meso γ scale vortices located in the meso β scale convergence line moved from Wuwei city to Wuhu city which caused the major rainfall. Mesoγscale vortices and rain band moved in the meantime. These vortices lasted for more than two hours and played an important role on the heavy rain. At the same time, It showed that the mesoγscale vortices occurred frequently in the north part of the rain band which dissipated quickly in the local area. After two and half hours, these vortices were vanished. The southwest moisture flow and west dry-cold flow combined which caused a meso βscale convergence line at the low level. The convergence line became dissipation according as rainfall weaked. The threedimensional kinematic structure model were also given.