摘要
利用LAPS(local analysis and prediction system)同化系统融合多种观测资料,对2010年8月25日发生在上海的一次强对流天气过程进行中尺度分析。结果表明,这次强对流天气主要是由中、低空中尺度辐合系统直接触发形成的。强对流形成阶段,地面有分散辐合形成并逐渐加强,成为触发中尺度垂直环流的主要机制,垂直结构上出现低层辐合高层辐散的有利配置,风暴中心附近出现明显的上升气流区,中高层相对湿度显著增加。成熟阶段,强对流云体中心附近的对流层底层开始出现下沉气流,上升气流在其拖曳作用下明显倾斜。衰减阶段,下沉气流加强使中尺度环流动力结构和水汽供应受到破坏,垂直结构上转为底层辐散高层辐合。因此,与天气尺度分析相比,基于LAPS的中尺度分析能更深刻地揭示中小尺度系统的三维结构和时空演变特征。
A process of severe convection occurring in Shanghai on August 25,2010 is analyzed by u-sing LAPS （local analysis and prediction system） analysis field to assimilate various meteorological da-ta. Results showed that the storm was trigged directly by mesoscale convergence systems on middle and lower layers. The convergence lines on surface developed into strong ones in the formation stage and became the major triggering mechanism of the mesoscale vertical circulation. In the meantime, the verti-cal structure contributed to the mesoscale convection development because of the convergence on mid-dle layer and the divergence on high layer. The prominent updraft zone located near the storm center, and the relative humidity grew significantly on middle and high layers. In the mature stage, the down-draft drag, which occurred on low layer near the storm centre, made the updraft more slantwise. The me-soscale circulation structure and moisture supply were destroyed in the decaying stage, and the vertical structure was contrary to that in the formation stage. The LAPS analysis field has an advantage in spatial and temporal resolution, which well revealed the spatial structure and development process of meso and small scale systems in the mesoscale analysis.
出处
《大气科学学报》
CSCD
北大核心
2012年第4期391-403,共13页
Transactions of Atmospheric Sciences
基金
上海市科委世博科技专项(10dz0581300)
上海市自然科学基金资助项目(09ZR1428700)
