春季西南热低压的发生发展与结构特征

Genesis,Development and Structure Characteristics of Southwest Heat Low in Spring

通过普查1997—2006年3-5月典型西南热低压天气过程,分析其气候特征,归纳热低压的生命史,将其分为4个不同的发展阶段:初生、成熟、相持和填塞。利用台站观测资料和NCEP 1°×1°及2.5°×2.5°再分析资料,对7次典型的春季西南热低压过程进行合成分析,揭示了成熟阶段和填塞阶段热低压结构特征。分析结果表明:在春季西南热低压系统控制下,气压降幅显著,气温升高、相对湿度降低,午后偏南风加大,气象要素具有明显的日变化特征;68%的热低压会给西南地区造成35℃以上的高温,32%的热低压给贵州造成高温。热低压系统为浅薄暖性低压,干区深厚,低压区为辐合区、正涡度区,以上升运动为主,并且是对流性不稳定。热低压填塞阶段,受冷空气侵入,低压北侧偏北风加大,近地层气旋的辐合增强,低压内为高能区,在冷空气的向南推进过程中,易出现强对流天气。

Climatic characteristics and life characteristics of southwest heat low are analyzed through survey from March to May of 1997--2006. In view of synoptic point, it can be divided into four developing stages： primary, mature, maintenance and decay. Based on the station observational data as well as NCEP re- analysis data, the typical southwest heat lows in spring are analyzed and the structural characteristics are revealed. The diagnostic results show that under the control of southwest heat low in spring, pressure de- creasing and temperature increasing are significant, and meteorological elements have obviously diurnal variations. Southwest heat low is a shallow warm low, but with deep dry zone. The low zone is characterized by convergence and positive vorticity. This system is of convective instability.