Abstract:

The research on the distribution of cloud water content and its evolution rules has important significance for the exploitation and utilization of regional cloud water resources. The paper analyzed the temporal variation characteristics of liquid water path (LWP) and integrated water vapor (IWV) in central Guanzhong Plain by using observation data of MWP967KV ground-based microwave radiometer at Jinghe station of Shaanxi Province from October 2017 to December 2020. Combined with ground precipitation and Doppler weather radar observation data, the development and evolution characteristics of water vapor and liquid water before precipitation in various cloud systems were compared by some cases study. The results indicate that the IWV exhibits obviously seasonal variations in central Guanzhong Plain, with the highest in summer, followed by autumn and spring, and the lowest in winter. Specifically, the peak appears in July, and the valley appears in December. The LWP is higher in autumn and summer, in winter it is the lowest. Notably, the peak is in September, and the valley is in December. The distribution of the IWV and LWP exhibits a single peak and single valley pattern over the course of a day, but the occurring time of their peak and valley is different. The diurnal maximum of the IWV occurs from 07:00 to 08:00 in summer and autumn, 23:00 in spring and 13:00 in winter, while the diurnal minimum of the IWV occurs at about 12:00 in spring, summer and autumn, 22:00 in winter. The diurnal maximum of the LWP occurs from 07:00 to 09:00 in spring, summer and autumn, while in winter it is slightly late (10:00). The diurnal minimum of the LWP appears at the nighttime in all seasons. The growth time of cloud water content before precipitation is different for different types of cloud systems. On average, the development time of stratiform cloud systems is 15.6 hours, and for other cumulus cloud systems it is 9.0 hours. In the initial stage, the IWV in both cloud systems varies prior to the LWP, and the fluctuation amplitude is increasingly violent as precipitation approaches. Additionally, the LWP in both cloud systems firstly exhibits a sudden violent increase before the rainfall being triggered, and the IWV and LWP in stratiform cloud system vary greatly in different seasons as precipitation is triggered. In the afternoon, the duration of strong convection developing is short, with an average time of 30 minutes. In the initial stage of development and before precipitation, the LWP varies and jumps sharply at the first.

Key words: ground-based microwave radiometer, water vapor, liquid water, temporal distribution, jumpily increase, central Guanzhong Plain

摘要：

大气云水含量分布及演变规律研究对于区域云水资源开发利用意义重大。利用2017年10月至2020年12月陕西泾河站MWP967KV型地基多通道微波辐射计探测资料，分析关中平原中部大气云水含量时间变化特征，并结合地面降水和多普勒天气雷达观测资料，通过个例对比分析不同云系降水前水汽和液态水发展演变特征。结果显示：关中平原中部水汽夏季最高，秋季次之，冬季最低，峰值在7月，谷值在12月；液态水秋季和夏季较高，冬季最低，峰值在9月，谷值在12月。水汽和液态水均呈现单峰单谷型日变化，峰谷出现时间存在差异，水汽日峰值夏季和秋季在07：00—08：00（北京时，下同）、春季在23：00、冬季在13：00，日谷值春夏秋三季在12：00前后、冬季在22：00；液态水日峰值春夏秋三季在07：00—09：00、冬季略晚（10：00），日谷值均在夜间。不同类型云系降水前云水含量增长用时不同，层状云系发展用时平均为15.6 h，其他积状云系平均为9.0 h，初期水汽均先于液态水发展，越临近降水时刻波动幅度越大，但降水触发前液态水率先跳变跃增，且不同季节层状云系触发降水时的水汽和液态水差异较大；午后强对流发展用时较短，平均为30 min，发展初期和降水触发前均是液态水率先变化和跳变跃增。

关键词: 地基微波辐射计, 水汽, 液态水, 时间分布, 跃增, 关中平原中部