Abstract: 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.

Key words: Microwave radiometer, Atmospheric water vapor, Liquid water