利用双频微波辐射计测空中水汽和云液水含量的个例分析

Case Analysis of Precipitable Water and Cloud Liquid Water Measured by Dual-Frequency Microwave Radiometer

利用23.8GHz和31.65GHz双频地基微波辐射计观测资料,结合卫星云图、雷达、探空和自记雨量计等资料分析了2005年4月在河南新乡观测的不同云系影响时大气垂直积分含水量(V)和云中液态含水量(L)的演变特征,对4月8日低槽云系影响时V、L的特征进行了分析。结果表明:双频辐射计对空中水汽和液态水反映灵敏,不同天气背景时对应有不同的V、L值分布。云液水含量L的变化与云量的增减有关。降水开始之前,水汽含量V值有明显波动,液态水含量L值也有明显增加,一般增大到0.4mm时即出现降水。这些现象对降水开始有指示意义,可预测云系正处于降水产生的阶段,可应用于人工增雨作业。此外,根据微波辐射计观测资料分析了大气水汽、云液水和地面降水之间的定量关系,云中液态水仅占汽态水的8.7‰左右,落回地面的降水占空中水汽量的18%左右。

By using the data from the ground-based dual-frequency microwave radiometer of 23.8 and 31.65 GHz, satellite cloud picture, the data from weather radar, radiosounding and self- recording rain gauge, analyzed was the evolution of atmospheric integrated precipitable water （V） and cloud liquid water content （L） obtained in different cloud conditions in April of 2005 in Xingxiang, Henan. Special analysis was focused on the effect of low trough cloud system on April8. The results showed that the radiometer is sensible to the water vapor and liquid water in clouds, and different V and L correspond to different weather background. The variation in L is related to the increasing or decreasing of cloud water content. There is an obvious fluctuation in L before rain and increase significantly during rain. Generally when L reaches 0.4 mm, the precipi- tation happens. This reveals that cloud is developing and will rain. In addition, the relationship among the three kinds of atmospheric water, i.e., precipitable water, cloud water and precipitat- ing water, was analyzed based on the observation data. The results showed the ratio of L and V is 0. 0087, whereas the rainfall amount is only 18% of precipitable water.