青藏高原那曲夏季云中水成物分布特征的毫米波雷达观测

结合2014年7—8月第三次青藏高原大气科学试验获得的毫米波雷达资料与探空温度资料,利用模糊逻辑法反演了西藏那曲地区夏季云中水成物的相态并对其分布特征开展了研究。首先,分析了层积云、雨层云以及深对流云的典型个例,发现三类云反射率因子、多普勒速度、速度谱宽以及退偏振因子垂直分布均有较大差别,相应的云中水凝物的回波特征与相态分布差别也较大。其次,研究了液相、混合相和冰相云层的云雷达探测特征,发现液相云层在0℃层以下的暖云层和0℃层以上的过冷水云层均具有反射率因子高值中心,混合云层的反射率因子高值中心随高度上升变化不大,冰云层的反射率因子高值主要集中在6 km以上,且随高度上升而趋于集中;三种相态云层出现频率高值分别集中在地面以上1、2～3、3～4 km高度层;液相云层在上午出现频率最高,混合相云层高频率发生在下午,冰相云层在晚上的出现频率最高。三种相态云层出现在上午的高度与下午和晚上相比较低,出现在晚上的高度范围最大;液相云层厚度一般小于0.3 km,冰相云层云顶位于9 km左右高度层时平均厚度最大,中云内的混合相和冰相厚度变化较小。

Millimeter Wave Radar Observation of Hydrometeor Distribution Characteristics of Cloud in Summer in Nagqu, Qinghai Tibet Plateau

Based on the millimeter wave radar data and sounding temperature data obtained from the third Qinghai Tibet Plateau Atmospheric Scientific Experiment during July-August 2014, this study inverses the phase of cloud hydrometeor in summer in Nagqu, Tibet with the fuzzy logic method and conducts analysis research on its distribution features. Firstly, the typical cases of stratocumulus, nimbostratus, and deep convective clouds are analyzed, and it is found that the vertical distribution of reflectance factor, Doppler velocity, velocity spectrum width and depolarization factor of the three types of clouds are quite different, and the characteristics of radar measurements and distribution of hydrometeor phase are also quite different. Secondly, radar reflectivity characteristics of liquid, mixed and ice clouds are studied, which shows that both warm clouds and supercooled water have high value centers of reflectivity factor. The reflectivity distribution center of mixed clouds is invariable with height. The high reflectivity factor of ice cloud is mainly over 6 km and tends to concentrate with the increase of altitude. The high frequencies of the three phase clouds are concentrated at the heights of 1 km, 2-3 km and 3-4 km above the surface respectively. The frequency of liquid phase clouds is the highest in the morning, the frequency of mixed phase clouds is high in the afternoon and the frequency of ice phase clouds is the highest in the evening. The heights of three phase clouds in the morning are lower than that in the afternoon and evening, and the perpendicular range maximizes at night. The thickness of liquid phase clouds is generally less than 0.3 km, and the average thickness of ice phase clouds is the largest when the top of ice phase clouds is located at about 9 km height, while the thickness of mixed phase and ice phase in mid level clouds varies only a little.