闽东降雪天气过程环流背景与物理量诊断分析

Diagnostic analysis of circulation background and physical quantity of snowfall process in Mindong district of Fujian province

通过对闽东地区近10年历史资料的分析与总结,研究降雪过程的大尺度环流背景、中尺度影响系统,诊断各物理量条件的变化.利用自动站实况资料、6 h间隔的NCEP1°×1°再分析资料,采用GRADS作图对资料进行客观分析,研究降雪天气过程中水汽条件、动力条件、温度层结等的分布特征.研究发现,闽东降雪发生在东亚稳定的纬向环流形势背景下,北半球上游,强大的经向环流和阻塞高压使中纬度东亚地区和西太平洋纬向环流得以维持.700 h Pa低层切变和低涡东移有利于冷暖空气的交汇,使得暖湿气流沿冷空气垫抬升凝结,850h Pa低空急流形成较强的水汽通道和能量通道.散度场和涡度场的垂直结构变化对降雪有较好的指示意义,且两者的斜压性与冷空气的入侵有较好的对应关系.温度层结是降水相态转化最重要的因素之一,中低层逆温是产生降雪较有利的条件.

Based on the analysis and summarization of ten years＇ historical data in Mindong district of Fujian province, this paper studies the large-scale circulation background, the mesoscale influence system and the change of the ptlysical conditions of the snowfall process. Based on the NCEP 1°×1° reanalysis data at 6h intervals, the data were analyzed by GRADS. The distribution characteristics of water vapor conditions, dynamic conditions and temperature stratification during snowfall were studied. It is found that in the back- ground of stable zonal circulation in East Asia, the strong meridional circulation and blocking high pressure in the northern hemisphere maintain the latitudinal circulation in the East Asia and the Western Pacific. The low-level shear and low-vortex eastward of 700hPa are favorable for the intersection of cold and warm air, and the warm and humid airflow is condensed along the cold air cushion. 850hPa low-level jet forms strong water vapor channel and energy channel. The variation of vertical structure of divergence field and vorticity field has good directive significance for snowfall. The baroclinic nature of both has a good corresponding relationship with the intrusion of cold air. Temperature stratification is one of the most important factors for the transformation of the precipitation phase and the inversion of the middle and low layers is a favorable condition for producing snowfall.