孟加拉湾风暴Mala结构及对云南强降水的影响

Structure of the tropical cyclones Mala over Bay of Bengal and effect on Yunnan severe precipitation

利用实时观测资料和NCEP(1°×1°)的6 h再分析资料,对2006年春季发生在孟加拉湾的超强风暴Mala的移动路径、强度变化、环流背景以及风暴温湿场、动力场特征等进行分析。结果表明:Mala在阿拉伯副热带高压和西太平洋副热带高压两高间辐合区生成、加强,并沿西太平洋副热带高压西侧西南或偏南气流移动。风暴发展、成熟到消亡,湿度对风暴的作用比温度明显;动力场结构除具有台风结构的一般特征外,在风暴发展期,中心附近散度场从低层到高层为辐合和辐散交替结构,表明风暴内部高空辐散抽吸作用对于风暴发展起到重要作用。登陆后风暴低压内自身能量和水汽与冷空气共同作用下,在冷暖交汇处出现强烈的上升运动和激发出中尺度辐合线是造成云南强降水主要原因。

The movement track, vibration-resistant pressure, circulation background, characteristics of air temperature and humidity fields, and of dynamic fields of the tropical cyclones Mala over the Bay of Bengal originated in 2006 springtime are analyzed based on the real-time observation data and NCEP 6- h reanalysis data with resolution 1°×1°. The results show that the Mala was originated and strengthened in the convergent area between the Arabia subtropical high and the western north Pacific subtropical high, and moving along south-west or south current over west side of the western north Pacific subtropical high. Compared to the differences made by humidity and temperature, humidity has a more obvious effect on the Mala during its＇ origination, mature and regression. Except Mala＇s same normal dynamic field features as typhoon, it has an alternated structure of convergence and divergence from low level level to high level of divergence field nearby the center. The phenomenon shows that the pumping in the Mala was processed by relaying. Under the co-effect of the Mala＇s inner energy caused by low pressure, vapour and cold air, severe rainfalls in Yunnan Province were mainly caused by tough air upward movement and mesoscale convergence line in the warm and cold confluent area.