Abstract:

Based on the observation data of TP/WVP-3000 Microwave Radiometer from the Semi-Arid Climate Observatory and Laboratory of Lanzhou University, the characteristics of water vapor and cloud liquid water content before precipitation and during non-precipitation processes were analyzed in arid and semi-arid region in summer from 2007 to 2010. Results are as follows:(1) The value of water vapor content reached 2.20 cm can be used as a threshold of precipitation forecast in semi-arid area. When the water vapor content is greater than 2.20 cm within 24 hours before the rainfall and its variability rate reaches 0.06 cm/h, or the water vapor content is small at the beginning, and then exceeds 2.20 cm with the increase of variability of the water vapor content to 0.19 cm/h before the precipitation, which may be forecast precipitation in future. (2) The cloud liquid water content with 0.20 mm can be used as a threshold of precipitation forecast, and when it appears a turning-point before precipitation with time, subsequently the variability rate increases, which can be used to forecast precipitation after one hour.

Key words: microwave radiometer, water vapor content, cloud liquid water content, precipitation threshold

摘要：

利用兰州大学半干旱气候与环境观测站2007～2010年夏季地基12通道微波辐射计观测数据，对半干旱区降水前和非降水过程的水汽含量和云液态水含量的变化特征进行分析。结果表明：（1）水汽含量达到2.20 cm可以作为半干旱区降水预报的阈值。水汽含量随时间变化比较平缓，变率约为0.06 cm/h，且降水前24 h内水汽含量均>2.20 cm；或者水汽含量开始较小，但降水前水汽含量随时间出现拐点，之后变率开始增加，可达0.19 cm/h以上，进而使水汽含量>2.20 cm。这2种情况均可预报可能有降水产生；（2）云液态水含量达到0.20 mm可以作为降水预报的阈值，且降水前云液态水含量随时间变化出现拐点，之后变率开始增加，可以预报1 h后可能有降水。

关键词: 微波辐射计, 水汽含量, 云液态水含量, 降水阈值