六盘山区夏秋季大气水汽和液态水特征初步分析

Characteristics of atmospheric water vapor and liquid water in Liupan Mountain area in summer and autumn

六盘山区是中国典型的农牧交错带和生态脆弱带,也是黄土高原重要的水源涵养地、生态保护区及国家级扶贫开发区。利用2017年611月隆德气象站地基多通道微波辐射计资料,结合同期平凉探空站及隆德地面降水等观测资料,分析了六盘山区夏秋季大气水汽、液态水变化特征。结果表明:六盘山区夏秋季在降水天气背景下,大气水汽含量和液态水含量均较高,分别为无降水天气背景下的14倍和70倍;降水天气背景下水汽在5000m以下有明显的增加,且在此高度范围内的水汽密度随高度的递减率比无降水天气背景下明显偏小;各高度层的液态水相比无降水天气背景下均有明显增大,除6月外,主峰值均出现在0℃层高度层以下。六盘山区夏秋季各月中,69月。大气水汽含量高值区均出现在正午到傍晚时段,低值区均出现在日出前后;液态水含量在日出前、午后及傍晚分别出现峰值,最明显的峰值出现在午后。对一次对流性降水天气过程分析后发现,降水发生前40min大气水汽含量和液态水含量出现两次明显的跃增,水汽向上输送不断加强,25007500m高度的相对湿度明显增大。

The Liupan Mountain area is a typical ecotone and ecologically fragile zone in China.It is also an important water conservation area,ecological reserve and national poverty alleviation development zone in the Loess Plateau.Characteristics of atmospheric water vapor and liquid water in the area of Liupan Mountain in summer and autumn were studied using the observations from a multi-channel microwave radiometer at the Longde weather station,the sounding data in Pingliang and surface precipitation data in Longde.The results showed that atmospheric water vapor content and liquid water content on rainy days over the Liupan Mountain in summer and autumn are about 1.4 and 7.0 times higher than those on clear days,respectively.On rainy days,water vapor increases obviously below 5 km and the decreasing rate of water vapor density with the increase of height is significantly smaller than that on clear days.Liquid water content at different altitudes also increases compared with that on clear days,and the major peak of liquid water content occurs below the altitudes where temperature is about 0℃.Atmospheric water vapor content has higher values in the period from the afternoon to the evening from June to September and has lower values near the sunrise.While for the liquid water content,the peaks occur near the sunrise,in the afternoon and evening,with the most possible one in the afternoon.A convective precipitation event is examined in this study.During this event,the atmospheric water vapor content and liquid water content increased twice within 40 minutes before precipitation,the upward transport of water vapor continuously enhances,and the relative humidity between altitudes of 2500-7500 m increases significantly.