Abstract:

Under the background of climate warming, the global drought risk increases, especially in the arid and semi-arid region of northwestern China, which is highly sensitive to climate change, and the drought seriously restricts the sustainable development of regional economy. The scientific development of cloud water resources is an effective way to solve the shortage of water resources in this region. Based on the ground-based multi-channel microwave radiometer data and conventional meteorological observation data at Yongdeng national meteorological observation station in Gansu, the spatial and temporal distributions of atmospheric water vapor and liquid water in eastern section of the Qilian Mountains were analyzed, and their evolution characteristics before rainfalls with different properties were discussed. The results are as follows: (1) Under the influences of atmospheric circulation, topography, boundary layer and local and regional weather and climate conditions, etc., the atmospheric water vapor more than 98% in eastern section of the Qilian Mountains concentrated below 6.0 km, and the water vapor density decreased with height, while the liquid water content firstly increased and then decreased with height. The water vapor density and liquid water content increased significantly on rainy days, and the height with the maximum liquid water content decreased. (2) The seasonal variations of water vapor and liquid water were obvious. The atmospheric precipitable water in summer was much more than that in winter, and the vertical extension of liquid water and the height with maximum content in summer were higher than those in winter. (3) The diurnal variations of water vapor and liquid water were obvious, and they had seasonal differences. The diurnal peak value of water vapor appeared from afternoon to nightfall, and the trough value appeared from morning to noon. The occurring time of peak and trough values of water vapor in summer half year were later than those in winter half year, and the variation range was larger. The vertical extension of liquid water in the daytime was higher than that in the nighttime, and the distribution of liquid water in summer half year was deeper than that in winter half year. (4) There were main periodic changes with about 10-20 days and 8 days of precipitable water vapor in eastern section of the Qilian Mountains, and the periods with 4-7 days and 21-32 days were obvious in summer and autumn. (5) The water vapor and liquid water jumpily increased before precipitation with different properties, but there were differences about jumping increment, time and height. The time of jumping increase was the earliest before cumulus-stratus mixed cloud precipitation from July to August in eastern section of the Qilian Mountains, and the increment was the maximum and the jumping height was the highest before cumulus precipitation, while the jumping height was lower significantly before the precipitation of warm cloud.

Key words: atmospheric water vapor, atmospheric liquid water, eastern section of the Qilian Mountains, temporal and spatial distribution, microwave radiometer

摘要：

气候变暖背景下全球干旱风险升高，而对气候变化高敏感的中国西北干旱半干旱区尤为突出，严重制约着区域经济的可持续发展，科学开发空中云水资源是解决该区域水资源短缺的有效途径。利用甘肃永登国家气象观测站地基多通道微波辐射计资料和常规气象观测资料，研究祁连山东段大气水汽和液态水的时空分布及不同性质降水前演变特征。结果表明：（1）受大气环流、地形、边界层及局地和区域天气气候条件等多因素影响，祁连山东段98%以上的水汽集中在6.0 km以下，大气水汽密度随高度下降，液态水含量则随高度先增后减。降水天气背景下，水汽密度及液态水含量明显增大，且液态水含量最大值出现高度有所降低。（2）水汽及液态水存在明显的季节变化，夏季大气可降水量远大于冬季，夏季液态水垂直伸展高度及最大值出现高度均大于冬季。（3）水汽及液态水日变化明显，且存在季节差异。水汽日峰值出现在下午至傍晚，谷值出现在清晨至中午；夏半年峰值及谷值出现时间较冬半年迟，且峰谷值变化幅度更大。液态水垂直伸展高度白天高于夜间，且夏半年垂直分布较冬半年深厚。（4）大气可降水量存在10~20 d和8 d左右的主周期，夏、秋季4~7 d和21~32 d的周期变化也比较明显。（5）不同类型降水前水汽及液态水均存在跃增现象，但跃增量、跃增时间及高度存在差异。其中，7—8月积层混合云降水前跃增时间最早，积云降水前跃增量最大、跃增高度最高，而暖云降水前跃增高度明显偏低。

关键词: 大气水汽, 大气液态水, 祁连山东段, 时空分布, 微波辐射计