摘要
利用常规天气资料和雷达资料对辽宁省2次不同影响系统暴雪过程的雷达回波特征及成因进行分析。结果表明:倒槽暴雪和蒙古气旋暴雪的雷达回波特征存在明显差异。倒槽暴雪时速度零线总体呈直线经过测站,风廓线上偏北风冷垫厚(1.5 km),强冷空气南下形成的强动力和持续降温作用触发降雪,虽然低层强冷空气下沉不利于降雪维持,但中层西南风增强和南北风径向辐合造成的辐合上升运动使得降雪维持并产生暴雪;在倒槽暴雪中,冷垫最厚、中低层西南风速最大提前于强降雪5 h,对暴雪预报预警有先兆意义。蒙古气旋暴雪降雪时速度零线由明显的"S"型迅速转为反"S"型,虽然风廓线上东北风冷垫浅薄,但由于降雪过程中总体维持偏南气流,有利于气旋暴雪产生;暖空气沿边界层冷垫的爬升增强了边界层动力作用;基本速度的旋转特征,表明冷暖空气交汇,辐合上升运动加强,当基本速度总体呈现偏北气流特征时降雪接近结束,这和倒槽暴雪明显不同,倒槽暴雪降雪时基本速度始终维持偏北气流特征。
The influencing system,characteristics of radar echoes and formation mechanism of two snowstorm weather processes caused by inverted-trough moving north and the Mongolia cyclone moving south in Liaoning were analyzed. The results indicated that there were significant differences about radar echoes for these two kinds of snowstorm weather. The zero speed line of radar presented straight through station and the cold air pad was thicker（ 1. 5 km） according to the vertical wind profile（ VWP） product during the inverted trough snowstorm process. A strong motivation and continuous cooling effect caused by strong cold air moving southward triggered the snowstorm,although low-level sinking cold air was not conducive to snowfall lasting,the vertical movement in middle level caused by southwest wind enhancement and radial convergence of north and south wind resulted in continuous snowfall and then the snowstorm occurred. During the inverted trough snowstorm process,it was a signal for forecasting and early warning five hours ahead of snowstorm that the cold pad was thickest and southwest wind velocity was maximum in the low and middle level. The zero speed line turned quickly from ＂S＂to anti ＂S＂during the Mongolia cyclone snowstorm,although the cold air pad was shallow according to the VWP,the southerly airflow maintained overall during the whole snowfall process,which caused the cyclone snowstorm. The base velocity of radar presented rotation character under the influence of the low-level cyclone,which led to convergence of cold and warm air,then the vertical movement enhanced at the low-level. When the basic velocity presented overall northerly flow feature,the snowfall was near the end,which was different from the inverted trough snowstorm（ the radial velocity presented consistent northerly wind feature）.
出处
《干旱气象》
2016年第5期836-840,865,共6页
Journal of Arid Meteorology
基金
辽宁省气象局课题(201416)
辽宁省暴雪专家团队共同资助
关键词
雷达回波特征
径向速度
风廓线
冷垫
中层辐合
radar echo characteristics
radial velocity
wind profiler
cold pad
middle-level convergence
