Formation Mechanism Analysis of a Heavy Rain in Shandong Province in Spring
Yang Xiaoxia Zhao Yu Gao Liuxi(Shangdong Meteorological Office, Jinan 250031)
By using the analyzed and 6-hour prediction data provided by the T213 model, the causes of a heavy rain and the energy and moisture conditions were analyzed. The dynamic trigger mechanism was studied through analyzing the features of helicity and Q* vectors. The result shows that the heavy rain was influenced mainly by the low vortex at 850 hPa and the surface cyclone; the convergence and ascending motion in the center of the vortex and north of the cyclone center triggered convective instability energy release, resulting in the heavy rain. The low-level Southwest Jet provided sufficient moisture and instability energy. The strong positive helicity and the intensive convergence of Q* vectors at the low level in the raining area indicate that there was superposition of mesoscale and synoptic-scale ascending motions. Differing from summer heavy rains, the systems in the westerly belt played a dominant role in spring heavy rain formation, but the subtropical systems are weaker and cool and warm air motions were very active before and after the heavy rain.
【CateGory Index】： P458.121.1