关键词: 短时强降水, 风廓线雷达, 风场特征

Abstract:

Based on convertional weather stutions, automatic weather station, wind profiler radar data and NCEP reanalysis data, a short-time heavy rainfall occurring between Beijing and Tianjin on 30 July 2015 was analyzed, and the atmospheric wind field characteristics before precipitation was focused on. The results were summarized as follows:(1) Low-level jet appeared nearly two hours before the heavy rain, which not only provided sufficient moisture for outbreak of the short-time strong rainfall, but also established the convective instability stratification under 700 hPa and triggered the instability energy releasing.(2)The updraft appeared above 1 000 m about 90 minutes before the heavy rain , then its height was falling and thickness was increasing, and after 30 minutes, it achieved the most powerful. As the precipitation was near, the updraft began to weaken, and when the precipitation started, the sinking airflow rapidly occupied a dominant position. (3)Cold advection formed in the boundary layer 70 minutes before the heavy rain, and warm moist air flows climbed on it, which gathered water vapor and energy, and cold air on middle level began to invade and developed strongly. (4)The variation of low-level jet had close relationship with occurrence of heavy rain, but the change of rainfall intensity was not only associated with low-level jet, but also it was the result of joint action of water, power and thermal conditions.(5)  The water, power and thermal conditions accumulated and strengthened before precipitation occurrence, and this strong signal was generally in advance 60 to 120 minutes, which provided scientific basis for heavy rain nowcasting.

Key words: short-time strong rainfall, wind profiler radar data, wind field