广汉机场冬季低能见度类型及气象要素对比分析

根据广汉机场2011-2016年冬季(12-次年1月)能见度以及气象要素的常规观测资料,对低于1 600 m的低能见度事件进行分型,并对比分析不同类型低能见度事件的变化特征,以及能见度与气象要素之间的对应关系.结果表明:辐射冷却是广汉机场冬季低能见度事件发生的主要机制,其中晴空辐射型与阴天辐射-平流型发生频率累计达到62%,平均起始能见度均低于800 m,而阴天平流型与雨天蒸发型发生频率相对偏低,且平均起始能见度均高于1 000 m.低能见度日数的日变化特征:晴空辐射型表现为"一高一低",其他为"两高一低".相对湿度对低能见度的形成起关键作用,低于800 m的低能见度事件对应相对湿度均大于91%,其中晴空辐射型的相对湿度最集中,范围在94%～97%,阴天平流型的相对湿度最分散,范围为86%～97%.其他各气象要素在不同类型低能见度事件中所起的指示作用不同.基础能见度越低,在夜间长波辐射冷却或者平流、蒸发作用下,起始能见度低于1 600 m的概率就越大.

On Comparison Analysis of Meteorological Conditions in Different Types of Low Visibility at Guanghan Airport in Winter

According to the hourly visibility and meteorological observation data of Guanghan Airport from December 2011 to January 2016, the low visibility events with the visibility below 1600m have been classified, and the variation characteristics of different types of low visibility events been compared and analyzed, also the corresponding relationship between different types of low visibility and meteorological factors been explored. The results show that radiation cooling is the main mechanism of low visibility events in Guanghan Airport in winter. The cumulative frequency of radiation-advection events in clear sky and cloudy day is 62%, and the average initial visibility is lower than 800 m. The frequency of advection events in cloudy day and evaporation events in rainy day is relatively low, and the average initial visibility is higher than 1000 m. The diurnal variation characteristics of sunny radiation low visibility days are "one high and one low", which are obviously different from the diurnal variation characteristics of overcast radiation advection, overcast advection and rainy evaporation. Relative humidity plays a key role in the formation of low visibility at Guanghan Airport. The corresponding relative humidity of low visibility weather below 800m is greater than 91%. The relative humidity of clear radiation type is the most concentrated, ranging from 94% to 97%, and that of cloudy advection type is the most dispersed, ranging from 86% to 97%. Other meteorological elements also play different indicative roles in different types of low visibility events. The lower the basic visibility is, the greater the probability that the initial visibility is less than 1600m under the action of long-wave radiation cooling or advection and evaporation at night.