Abstract:

Based on conventional observation data from weather stations of Zhejiang Province and its surrounding and ERA-Interim reanalysis data from March to May during 2007-2016, the circulation characteristics and meso-scale conceptual model of warm sector rainfall processes in spring in Zhejiang Province were analyzed and summarized. The results show that the cloud was more, the precipitation was small, the temperature was high and the daily temperature difference was small during warm sector weathers in spring in Zhejiang Province. The warm sector rainfall processes were divided into four types according to 850 hPa wind field, and they were the southwestern airflow pattern, warm shear northward extending pattern, cold shear approaching pattern and southeastern airflow pattern, respectively. The warm sector rainfall for cold shear approaching pattern was the strongest, and then followed by warm shear northward extending pattern, their precipitation was large in the southwest and was small in the northeast, while that for southeastern airflow pattern was the smallest. Meso-scale analysis found that the warm sector rainfall often appeared in the dense isoline area of θ_se on 850 hPa and the convergence upward area of intersection of southeasterly airflow near surface and low-level southwesterly airflow over the coastal of Zhejiang, and rain belt paralleled to θ_se isolines. The baroclinic instability which caused by residual cold air near surface and temperature difference between land and sea could significantly increase the precipitation of warm sector.

Key words: warm sector rainfall in spring, weather patterns, circulation characteristics, meso-scale structure

摘要：

利用2007—2016年春季浙江及周边地区气象站观测资料与ECMWF再分析资料,分析总结浙江省春季暖区降水天气过程的环流特征及中尺度概念模型。结果表明:浙江春季暖区天气具有云量多、雨量小、气温高、日温差小的特点,暖区降水的环流形势可分为西南气流型、暖切北抬型、冷切靠近型、东南气流型4类;冷切靠近型降雨最强,其次为暖切北抬型,雨量分布均表现为西南部大、东北部小,而东南气流型降雨最小。中尺度分析发现,浙江春季暖区降雨出现在沿海近地层东南气流与低层西南气流交汇的辐合上升区、850 hPa等θ_se线密集区,雨带走向与等θ_se线平行;近地层残留的冷空气和海陆温差造成的斜压不稳定可导致降水明显增强。

关键词: 春季暖区降水, 天气分型, 环流特征, 中尺度结构