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当前位置: 首页 > 文章 > 豫西山区一次回流暴雪天气成因分析 宁夏农林科技 2018 (6) 45-47,63
Position: Home > Articles > 豫西山区一次回流暴雪天气成因分析 JOURNAL OF NINGXIA AGRICULTURE AND FORESTRY SCIENCE AND TECHNOLOGY 2018 (6) 45-47,63

豫西山区一次回流暴雪天气成因分析

作  者：
杜晓民
关键词：
暴雪;回流;地形;影响系统;次级环流;水汽输送
摘  要：
利用NCEP再分析资料对2017年2月21日豫西山区一次回流暴雪天气过程进行分析.结果表明:较强的西南暖湿气流使槽前的上升运动增强,不仅为暴雪区上空输送了水汽,而且有利于不稳定能量的集聚,槽后冷平流对能量的释放起触发作用.低涡前切变线与低空西南风急流左侧较强辐合区相配合为暴雪的产生提供动力抬升条件.回流冷空气长时间影响,使暴雪区辐合上升运动增强."天南地北"形势场,使风的垂直切变加大,对称不稳定增强,降雪强度增大.低层回流冷空气使低层大气长时间维持大湿度区,并与上层东移的大湿度区相叠加,增加了湿层厚度,有利于降雪持续而形成强降雪.低层回流的偏东风遇到地形后引起上升运动,与上游700~850 h Pa的低值系统前部的上升运动汇合形成深厚的、大范围的强烈上升运动是产生强降雪的关键性条件.锢囚锋产生的锋面次级环流与回流冷空气遇地形阻挡产生的正、逆环流圈,伴随着较强的垂直上升运动,对强降雪有重大贡献.由锋面造成的温度梯度、风的垂直切变及地形作用在暴雪区形成的对称不稳定和中低层西南暖湿急流产生的对流性不稳定,有利于暴雪形成.
作  者：
DU Xiao-min;Lushi Meteorological Bureau;
单  位：
DU Xiao-min%Lushi Meteorological Bureau
关键词：
Snowstorm;;Back flow;;Terrain;;Influence system;;Secondary circulation;;Water vapor transport
摘  要：
NCEP reanalysis data set was used to analyze a circumfluence snowstorm in western Henan mountain areas on Feb.21, 2017. The results showed that the stronger southwest warm and wet air strengthened the ascending motion in front of trough. It not only transported the water vapor, but also contributed to the accumulation of unstable energy. The cold advection behind trough triggered the energy release. The vortex with front shear line and the convergence area on the left of the southwesterly low-level jet provided dynamic lifting conditions for the snowstorm. The long-term effects of backflow cold air increased the convergence ascending motion in the snowstorm area. The position field increased the vertical wind shear.The symmetric instability was enhanced and the snowfall intensity increased. The return cold air at the low level made the lower atmosphere in a high humidity area for a long time and stacked with the high humidity area moving eastward at the high level, which increased the thickness of the wet layer and snow continued to fall and formed heavy snow. The ascending motion occurred when the return east wind at the lower level encountered the topography. It converged with the ascending motion in front of the low-pressure system of upstream 700~850 h Pa and the deep and extensive ascending motion was formed. This was critical to the occurrence of heavy snowfalls. Accompanied by strong vertical ascending motion, the positive and negative circulation occurred when the frontal secondary circulation due to the occluded front and the return cold air was obstructed by the topographic barrier. This was favorable for the heavy snow. The symmetric instability affected by the front-caused temperature gradient, vertical wind shear and topographic effects and the convective instability due to west-south warm and wet jet stream, which facilitated the formation of heavy snow.

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