Abstract:

Based on Doppler radars data at Wuhan, Zhumadian, Hefei and Fuyang, the wind field structure of a rainstorm process which occurred in Hubei Province from 00:30 to 06:30 on 9 June 2008 was retrieved and analyzed by using the two-step variational method. And on this basis the retrieved wind fields in middle and lower troposphere were compared with NCEP reanalysis data. The results show that the wind field structures at 3 km and 5.5 km height retrieved by the two-step varational method basically agreed well with the 700 hPa and 500 hPa wind field from the NCEP data, which means that the retrieval of the major structure of wind fields by using the two-step variational method during the rainstorm process was greatly feasible. The evolution of half-hourly retrieved wind fields indicated that the reflectivity of Doppler radar gradually weakened with the intensity and area of divergence in middle and lower troposphere increasing, which was helpful to weaken updraft airflow and southerly water transport airflow, and caused damage to the moisture conditions of the convective cloud system maintaining.

Key words: two-step variational method, Doppler radar, rainstorm, wind field structure

摘要：

利用武汉、驻马店、合肥、阜阳4部多普勒天气雷达资料，采用两步变分方法对2008年6月8日08时至9日08时发生在湖北省的一次暴雨过程中00:30～06:30时段内的风场结构进行了反演分析，并与同时段的NCEP再分析资料进行对比。结果表明，两步变分法反演的风场结构与NCEP再分析资料的风场结构基本吻合，证明了该方法的风场反演能力。对反演的风场结构的演变分析可知，此次降水过程减弱的主要原因是：对流层中低层风场辐散的出现及辐散强度和范围的扩大，使得输送水汽的偏南气流和上升运动减弱，对流云系降水的基本条件受到破坏。

关键词: 两步变分法, 多普勒雷达, 暴雨, 风场结构