“20·6”广西持续性暴雨过程异常气候特征分析

Analysis of abnormal climate characteristics of the“20·6”persistent rainstorm process in Guangxi

利用广西91个地面气象观测站逐日降水资料以及NECP/NCAR高度场的再分析资料,对“20·6”广西持续性暴雨过程异常特征进行分析。结果表明:(1)欧亚中高纬呈“两槽一脊”环流形势,东亚大槽加深,冷空气南下活跃,有利于广西东北部强降水发生和维持。(2)南海夏季风爆发偏早,南海夏季风活跃,打通来自印度洋和南海水汽通道。(3)副热带高压位置偏北、西脊点位置偏西,来自副热带高压南侧的东风气流与孟加拉湾西南暖湿气流汇合,有利于强降水发生和维持。(4)此次过程前期热带大气低频振荡对流抑制带有明显向东移动,并稳定维持在西太平洋,热带大气低频振荡对流带活跃于印度洋,为广西暴雨发生带来丰富的水汽。以上条件有利于广西持续性暴雨过程的发展和维持。

Based on the daily precipitation data of 91 surface meteorological stations in Guangxi and the reanalysis data of the NECP/NCAR geopotential height field,the abnormal characteristics of the“20·6”continuous rainstorm process in Guangxi were analyzed.The results showed that:(1)there were good divergence conditions at high levels,which were conducive to the occurrence and maintenance of heavy precipitation in northeastern Guangxi.The circulation situation of“two troughs and one ridge”,the deepening of the trough on the eastern side and the eastward movement of the split trough were also conducive to the occurrence and maintenance of heavy precipitation in northeastern Guangxi.(2)The onset of the South China Sea summer monsoon was early,and the South China Sea summer monsoon was active,leading to the establishment of water vapor channels from the Indian Ocean and the South China Sea.(3)The subtropical high was located northward and its western ridge point was located westward.The easterly airflow from the south side of the subtropical high converged with the warm and humid southwesterly airflow in the Bay of Bengal,which was conducive to the occurrence and maintenance of heavy precipitation.(4)In the early stage of this process,the convection suppression band of tropical atmos pheric low-frequency oscillation moved eastward obviously and maintained stably in the western Pacific.The convection band of tropical atmospheric low-frequency oscillation was active in the Indian Ocean,which brought abundant water vapor to the rainstorm in Guangxi.The above conditions were conducive to the development and maintenance of persistent rainstorm process in Guangxi.