利用地基多通道微波辐射计遥感反演华北持续性大雾天气温、湿度廓线的检验研究

Verification study of the atmospheric temperature and humidity profiles retrieved from the ground-based multi-channels microwave radiometer for persistent foggy weather events in northern China

地基多通道微波辐射计可提供高时间分辨率的大气温、湿度和液态水含量廓线遥感探测数据,为大气层结及云雾形成和演变特征研究提供了重要手段,但对其观测数据的可靠性检验研究很少。本研究在对比晴空MonoRTM模拟亮温和微波辐射计观测亮温的基础上,利用华北地区2009—2013年11个雾天气过程的170个时次(其中30个为雾发生时次)的探空数据,检验了美国Radiometrics 35通道MP-3000A型微波辐射计(Microwave Radiometer Profiles,MWRP)探测的温度、水汽密度和相对湿度数据,并结合系留气艇和CloudSat云雷达等观测资料,检验了典型雾个例的MWRP反演的温、湿度廓线数据。与探空数据的比较表明,两者的温度(T)数据的相关系数超过0.98,水汽密度(ρ)的相关系数超过0.95,但相对湿度(RH)的相关系数只有0.67左右。总样本误差分析中MWRP反演的T比探空偏低约3℃,ρ的均方根误差(E)在1 g/m^3以内,RH在1—7 km高度偏大,总样本RH垂直平均E在18%左右,雾天时的RH垂直平均E在23%左右。与系留气艇观测数据比较表明,MWRP反演的T也偏低,但两种探测方式的T和RH在指示雾的发展演变过程中具有很好的一致性。CloudSat云雷达数据验证了MWRP反演显示中高层出现高RH区与云的存在有关。

The ground-based multi-channels microwave radiometer can provide high temporal resolution profiles of the atmos pheric temperature, humidity and liquid water and has a potential application in investigating the formation and evolution of cloud and fog weather events. However, the verification studies of the data retrieved from the multi-channels microwave radi ometer are few. In this paper, the reliability of the microwave radiometer was tested by contrasting the brightness temperature simulated by the MonoRTM with that observed by the instrument. The temperature （T）, water vapor density （p） and relative humidity （RH） data retrieved from the Microwave Radiometer Profiles （MWRP） with 35 channels produced by the Radiomet- ries Corporation were examined by the radiosonde data of 170 times in which 30 times are in fog periods covering the 11 fog c- vents during 2009 - 2013 in northern China. The tethered balloon sounding and CloudSat cloud radar data were also used to ex amine the temperature and humidity profiles derived from MWRP for some typical fog events. The comparison of MWRP＇s pro files with radiosonde soundings shows that the correlation between two observational methods in terms of temperature data was higher than 0.98, and that in water vapor density data reached more than 0.95. The correlation between these two relative hu-- midity data was much lower, only about 0.67. In the error analysis of the overall samples, T retrieved from MWRP was lower about 3℃ than that from radiosonde sounding, the mean root mean square error （E） of ρ was less than 1 g/m3 , and RH from MWRP was larger than that from radiosonde sounding between the height of 1 and 7 km. The mean E of RH was 18% for o verall samples and 23~ for foggy samples. The comparison of profiles between the tethered balloon soundings and MWRP shows that the retrieved T from MWRP was also lower than that by tethered balloon, but both were in good agreement in indi- cating the development and evolution of fog events. The high RH at upper-levels retrieved from MWRP was relevant to the clouds as shown by the cloud radar data from CloudSat.