一次典型大范围冷流暴雪个例的诊断分析

A Diagnosis Analysis of an Ocean-Effect Snow in Shandong Peninsula on 30 December,2010

利用常规天气图和WRF模式模拟的数据,对2010年12月30日发生在山东半岛的一次冷流暴雪过程进行了天气学诊断分析。结果表明:(1)这是一次典型的大范围冷流暴雪过程,500hPa低涡位置偏南(43°N以南)、850hPa西北冷平流范围广,强度强是造成本次暴雪范围大的主要原因,为强冷流降雪的产生提供了有利条件。(2)降雪的水汽来自渤海,由西北风向山东半岛输送,并在半岛北部辐合;高湿区集中在850hPa以下,湿层较为浅薄。(3)降雪落区与高相当位温脊的位置存在着对应关系,强降雪通常发生在脊线附近;θe等值线向上凸起的高能区集中在750hPa以下,大气不稳定层结较低。(4)强烈的上升运动集中在对流层低层750hPa以下,上升运动越强,降雪量越大。⑸受地形影响,西北风吹向辽东半岛时转为东北风,西北风与东北风在渤海中东部至山东半岛形成切变线,切变线的方向和位置决定了降雪的强度与落区;风速在半岛北部低山丘陵前辐合,有利于产生上升运动,使得降雪加强。

An ocean-effect snow in Shandong Peninsula on 30 December 2010 was analyzed by synoptic and diagnosis analysis with conventional weather maps and simulative data of WRF numerical model. The results show that the snowfall was a typical ocean-effect snow in large area. The vortex （south of 43°N） on 500hPa and the wide and strong cold advection from to this snowfall in so large area. Bohai was the main transported to Shandong Peninsula by the northwest northwest on 850hPa were the main reasons that led moisture source of the snowfall and the moisture was wind and converged in the north of Shandong Peninsula. High humid region was mostly under the layer of 850hPa, and the humid layer was shallow. Snow drop zone had a close relationship with the location of the ridge of high equivalent potential temperature, where the heavy snowfall was located. High-energy region was mainly under the layer of 750hPa, and the atmospheric unstable layer was also shallow. The strong upward vertical movement was in the lower troposphere, and the stronger upward vertical movement was , the heavier the snowfall was. The northwest wind shifted to the northeast wind when passing across Liaodong Peninsula, and the two kinds of wind formed the shear line in the north of Shandong Peninsula. The direction and location of the shear line could affect the strength and the location of snowfall.