2017年初春贵州高速公路大雾天气分析

Analysis of Heavy Fog on Expressways of Guizhou Province in Early Spring of 2017

利用气象自动站和交通气象站逐分钟能见度观测资料和天气图资料,分析了2017年初春发生在贵州多条高速公路的持续性大雾天气形成原因,探讨了山区高速公路大雾天气应对措施。结果表明:高空槽东移影响,低空西南气流将南海水汽向贵州输送,静止锋系统东西摆动和长时间存在,是这次高速公路大雾过程的主要天气背景。在锋面天气系统影响下,相邻区域内海拔高度与能见度具有反相关性,海拔较高处能见度较低,大雾现象严重、持续时间较长,贵州高速公路因海拔相对较高更容易发生大雾。锋面逆温维持,大气层结稳定,有利于水汽在低空聚集,充沛的水汽和辐合有利于低云发展增厚、云底下降,从而导致近地面大雾形成和维持;随着逆温层减弱消失,稳定层受到破坏,不利于水汽聚集和低云发展,地面大雾也随之减弱消散。应对大雾天气需要特别注意隧道内外能见度反差较大的影响,以及锋面大雾天气因路面湿滑和低能见度双重因素的影响。

Based on the synoptic map and one-minute visibility data from automatic weather stations and traffic weather stations, the causes of persistent heavy fog occurred on 9 to 12 March 2017 on expressways of Guizhou were analyzed. The countermeasures of heavy fog weather on mountainous expressways were discussed. The results showed that heavy fog mainly occurred on the expressways under the influence of upper trough eastward movement, water vapor transports from the South China Sea to Guizhou by the southwest airflow, and the east-west shift and long-term existence of the static front system. Visibility in adjacent areas was negatively correlated with altitude because of the influence of frontal weather system. The fog was heavier and lasted for longer time at higher altitudes, resulting in lower visibility. Heavy fog was more likely to occur on expressways in Guizhou because of the relatively high altitude. Atmospheric stratification was stable under the frontal inversion, which was conducive to water vapor accumulation at low levels. The abundant water vapor and convergence was conducive to the development and thickening of low clouds and cloud bottom descent, resulting in the formation and maintenance of heavy fog near the ground. The stability layer was destroyed as the inversion layer weakened and disappeared. This was not conducive to water vapor accumulation and low cloud development, which was beneficial to the weakening and dissipating of the heavy fog. In order to deal with heavy fog weather, special attentions should be paid to the influence of contrasting visibility between inside and outside of tunnels, as well as the influence of wet road surface and low visibility in frontal heavy fog.