云贵高原东部锋面雾的特征及气象影响因子分析

Characteristics of Frontal Fog in Eastern Yunnan-Guizhou Plateau and the Analysis of Meteorological Impact Factors

利用19842013年贵州省84个国家级观测站地面气象观测资料,分析锋面雾的时空分布特征及其与气象影响因子的关系。结果表明:(1)锋面雾呈“西多东少”的分布特征,与云贵静止锋的位置及强弱、贵州西高东低的地势有关,73%的锋面雾出现在海拔高度为8001500 m的地区。(2)近30年贵州锋面雾日的年际变化呈缓慢下降趋势,每10年下降0.39天,贵州中西部地区锋面雾日呈减少趋势,这与气温升高、湿度降低有关;锋面雾主要出现在秋末至初春,以冬季为最多,日变化不显著,但夜间到早晨时段发生的频率最高。(3)在云贵静止锋背景下,气温2~6℃,气温日较差2~4℃,24 h变压和变温分别为-2~2 hPa和-2~2℃时,锋面雾发生的频率最大,表明较稳定的气压和温度对锋面雾形成有重要意义,强烈的升温和降温均不利于锋面雾的形成。锋面雾发生时地面风速小于等于4 m/s,风向以静风和偏东、偏北风为主,其次是偏南风,常伴随微量降水存在。

Based on the conventional meteorological data from 84 national observation stations in Guizhou Province from 1984 to 2013,the spatio-temporal distribution feature of quasi-stationary frontal fog and its relations with meteorological impact factors are analyzed.The results suggest that:(1)The spatial distribution of quasi-stationary frontal fog is characterized by a high frequency in the west and low frequency in the east of Guizhou.This is closely related to the position and strength of the Yunnan-Guizhou quasi-stationary front and the topography of“high in the west and low in the east”in Guizhou.Seventy-three percent of the frontal fog appears in areas with an altitude of 800—1500 m above sea level.(2)Overall,the annual variation of quasi-stationary frontal fog shows a slowly decreasing trend in Guizhou with a rate of 0.39 days per decade.The central and western part of Guizhou has a decreasing trend of frontal fog days,which is associated with the rise in temperature and the decline in humidity.The quasi-stationary frontal fog mainly occurs in late autumn to early spring,mostly in winter.Frontal fog occurs mostly from night to morning,but its diurnal variation is not obvious.(3)Under the background of Yunnan-Guizhou quasi-stationary front,temperature is 2—6℃with diurnal range being 2—4℃.When the 24 h surface pressure and temperature vary in the ranges of-2 to 2 hPa and-2 to 2℃,the frequency of frontal fog is the highest.This indicates that stable pressure and temperature have positive values to frontal fog events,but the sharp rise or drop in temperature is not favorable for the formation of frontal fog.When frontal fog occurs the surface wind speed is less than 4 m/s,the wind mainly tends to be calm wind,easterly wind or north wind,followed by southerly wind.In addition,frontal fog is often accompanied by little rainfall.