青藏高原东侧九龙夏季非降水云的观测特征

Observational characteristics of summer non-precipitating clouds in Jiulong on the east side of the Qinghai-Tibet Plateau

青藏高原东侧九龙地区是西南涡多发区,利用该地区新型探测设备开展云探测,有助于增强对西南涡多发区云特征的认识。利用2018—2019年6—8月九龙站地基微波辐射计资料,分析了该地区夏季非降水云的出现率、液态水路径及过冷水路径的观测特征。结果表明:九龙夏季非降水云出现率月均值在67%~82%之间,以低云和中云为主,高云较少;低云出现率表现为白天低、夜间高,而中云和高云则相反;云出现率的垂直分布表现为单峰形态,在约2km高度存在云出现率峰值8.1%;受大气热力层结日变化影响,云出现率的单峰垂直分布呈现日夜差异。另外,九龙夏季非降水云的液态水路径均值为0.433kg·m^(-2),其中低云、中云、高云的液态水路径均值分别为0.665、0.240、0.102kg·m^(-2);低云的液态水路径日变化特征与其出现率相似,而中云和高云的液态水路径日变化特征不明显。此外,九龙夏季非降水云中冷云的过冷水路径均值为0.154kg·m^(-2),其中低云、中云、高云的过冷水路径均值分别为0.065、0.166、0.102kg·m^(-2);总体上过冷水路径在液态水路径中的占比约为34.3%~38.8%,过冷水路径占比随云的高度而增大,这使得中云和高云的过冷水路径日变化与其液态水路径相似。与同纬度华中地区相比,九龙夏季非降水云具有明显不同的特征,这与两地之间的大气水汽特征差异密切相关。

Jiulong is located on the east side of the Qinghai-Tibet Plateau(QTP)and is a region prone to southwest vortex.Cloud detection with new-type detection equipment in this region helps enhance the knowledge of cloud characteristics in the southwest vortex-prone region.In this study,based on the ground-based microwave radiometer data from June to August of 2018-2019 in Jiulong,the observational charac-teristics of cloud occurrence frequency(COF),liquid water path(LWP),and supercooled liquid water path(SLWP)for non-precipitating clouds during the summer seasons are investigated.The results are as follows.The monthly average COF of summer non-precipitating clouds in Jiulong is between 67%-82%,with low and middle clouds being the main types,and high clouds being less common.For low clouds,the COF is low in daytime and high in nighttime,while it is the opposite for middle and high clouds.The vertical distribution of COF presents an unimodal pattern,with a peak of 8.1%at a height of about 2 km.Due to the diurnal variation of atmospheric thermal stratification,the uni-modal pattern of COF shows diurnal differences.Moreover,the average LWP of summer non-precipitating clouds in Jiulong is 0.433 kg·m^(-2),with the average LWPs of low,middle,and high clouds being 0.665,0.240,and 0.102 kg·m^(-2),respectively.The diurnal variation of LWP in Office of Torrential Rain and Disasters.OA under CC BY-NC-ND 4.0 low clouds is similar to their COF,while the diurnal variations of LWP in middle and high clouds are not significant.Additionally,the aver-age SLWP of cold clouds among summer non-precipitating clouds in Jiulong is 0.154 kg·m^(-2),with the average SLWPs of low,middle,and high clouds being 0.065,0.166,and 0.102 kg·m^(-2),respectively.On the whole,the proportion of SLWP in LWP is about 34.3%-38.8%.The proportion of SLWP increases with the height of the cloud,which makes the diurnal variations of SLWP in middle and high clouds similar to that of LWP.Compared with central China,the characteristics of summer non-precipitating clouds in Jiulong are significantly different,and this is closely related to the different characteristics of atmospheric water vapor between the two regions.