全天空红外云探测在航空气象中的应用

利用合肥新桥机场温湿度、云高、能见度以及全天空云图仪数据资料, 分析了 2019 年 7 月至 2020 年 4 月机场上空各类云的红外特征以及云、雾演变规律。结果表明: (1) 在云判别上, 云底高度越高, 红外云图上表现亮度越暗,反之亦然。且不同类型的云具有各自独有的红外特征。 (2) 不同高度的波状云最大云块平均最短直径表现为层积云云块是高积云的 2∼4 倍, 高积云是卷积云的 2∼4 倍。碎层云主要呈现出团状, 具有蓬松棉花状结构; 而碎雨云相对破碎,一般为烟带状或散片状。 (3) 云与雾有明确的转化过程。辐射雾一般发生在云层刚散开期间, 天空至少一半为晴空的时段, 且雾逐步抬升为云, 并持续消散。当天空形成不均匀缺口, 表明雾开始消散, 其可作为能见度迅速回升的一个重要指标。非对流降水云层演变呈现出云高由高到低, 云层由分散纹理状变为均匀层状, 降水前期均会出现“均匀层状”,地面相对湿度呈现出陡增现象。

Application of All-Sky Infrared Cloud Observation in Aviation Meteorology

Based on the data of temperature, humidity, cloud height, visibility and all-sky view imaging from theautomatic meteorological system of Hefei Xinqiao Airport, China, the infrared characteristics of all kinds of cloudsas well as the evolution of clouds and fog over the airport from July 2019 to April 2020, are analyzed. The resultsshow that: (1) the higher the cloud bottom height is, the lower the temperature is, which means that the higherclouds have the weaker thermal radiation resulting in the darker infrared cloud image, and vice versa. And differenttypes of clouds have their own unique infrared characteristics. (2) As for the average shortest diameter of the largestcloud block of wave clouds at various heights, that of stratocumulus is 2–4 times that of altocumulus, and that ofaltocumulus is 2–4 times that of cirrocumulus. Generally, fractostratus shows fluffy-cotton alike structures, whilefractonimbus are usually in the form of smoke band or scattered sheet. (3) There is a clear transformation processbetween cloud and fog. Radiation fog generally occurs during the period when clouds just disperse and at least halfof the sky is clear, and the fog gradually rises to clouds and continues to dissipate. When a breach is formed in thesky, it indicates that the fog begins to dissipate, which can be used as an important indicator for the rapid recoveryof visibility. The evolution of the non-convective precipitation cloud layer shows that the cloud base height changesfrom high to low, and the cloud layer changes from dispersed texture to uniform layer at the same time. The uniformcloud layer always appears in the early stage of the precipitation, and the relative humidity of ground presents asharp increase.