不同强度降水发生前微波辐射计反演参数的差异分析

Different characteristic analysis of inversion parameters for heavy rainfall and weak rainfall by microwave radiometer data

应用微波辐射计反演的地面至10 km 高度共58 层的相对湿度、水汽密度和云液态水的垂直廓线,以及大气水汽总量、云液态水总量和云底高度数据,再结合小时雨量资料对武汉站不同强度降水进行统计分析,按照降水初始时刻的雨强将武汉站降水分为三类：小时降水量大于等于5 mm 的强降水、小时降水量在1-5 mm 的中等强度降水和小时降水量在0.1～1 mm 的弱降水,统计结果表明：三类降水开始前,大气和近地面湿度均有显著增加;2 km 以下有水汽和云液态水的增量中心,且水汽增量中心比云液态水增量中心提前0.5-1 h;降水开始前1.5-1 h,水汽和云液态水的增长速度从缓慢增加突变为迅速增加.强降水开始前7 h 最大湿度达到饱和、云底高度下降;低层水汽含量增幅最大,云液态水总量显著高于另两类降水.弱降水开始前,大气与近地面湿度、水汽和云液态水的增加都出现得更早、更稳定,增量中心强度小、位置高,但大值区从降水开始时刻维持到降水开始后5 h,这决定降水能够持续较长时间.

Based on vertical profiles of relative humidity, water vapor density and liquid water with high resolution from ground to 10 km altitude, precipitable water vapor, path-integrated cloud liquid water and cloud base height data, combine with hourly rainfall data in Wuhan,three classes(19 cases) rainfall events with different rain intensities in the first hour are analyzed. Statistic results show that a significant increase of humidity in atmosphere and near the ground are necessary conditions before all classes of precipitation. The incremental centers of water vapor precede the incremental centers of liquid water for 0.5-1 hour below 2 km. At 1.5-1 hour before precipitation occurs, the growth rate of water vapor and liquid water change suddenly from a slow increase to a rapid increase. At 7 hours before heavy rainfall occurs, relative humidity saturated. Then, cloud base height decreases rapidly. Near heavy rainfall, the increase of path-integrated liquid water, water vapor and liquid water content in the lower atmosphere are significant with the maximum value and at the lowest altitude. Before weak precipitation,the increases of humidity in atmosphere and near the ground, water vapor and liquid water occurred earlier and are stable. Incremental centers with the minimum values and the highest altitudes result in the weakest raininess in the first hour. But, the high value centers maintain from precipitation start to 5 hours later, which leads to long time precipitation.