两种探空仪观测湿度垂直分布及其应用比较

对2010年8月在云南腾冲利用芬兰Vaisala RS80和低温霜点仪 (Cryogenic Frostpoint Hygrometer，CFH) 两种探空仪测量大气湿度的垂直分布进行对比分析，同时比较它们白天和夜间测量误差的差别，并对国产GTS1，RS80和CFH共3种探空仪测量水汽总量与地基GPS遥测结果进行比较。结果表明:RS80湿度测值在整个对流层比CFH测值偏干 (23.7±18.5)%；因太阳辐射白天RS80偏干较夜间更明显，比夜间偏干 (13.5±14.8)%。而在对流层上层向平流层过渡区域内RS80湿度数据基本无效。CFH在低温、低湿环境下对湿度能有效测量，但在湿度较高的对流层低层测值偏高，导致比较中CFH水汽总量平均比GPS遥测的水汽总量偏高 (4.3±2.0) mm (样本数为11)，而RS80，GTS1与GPS的水汽总量差别分别是 (0.2±1.4) mm (样本数为12), (-0.2±2.2) mm (样本数为43)。地基GPS遥测的水汽总量对对流层上层至平流层的水汽变化不敏感。由于RS80测量相对湿度在高空偏低，通过RS80相对湿度测值来确定中、高云结果是偏低的，特别是对6000 m以上的高云判别上，RS80相对湿度的探测几乎很难甄别到云的存在。

Inter comparision and Application of Atmospheric Humidity Profiles Measured by CFH and Vaisala RS80 Radisondes

Vertical profiles of atmospheric humidity simultaneously measured by balloon-borne Cryogenic Frostpoint Hygrometer (CFH) and Vaisala RS80 radiosonde in Tengchong, Yunnan in August 2010 are analyzed. Currently, CFH is the reference instrument in the measurement of atmosphere water vapor profile. RS80 radiosonde is ever extensively used in the world before the middle of 1990s. The humidity data measured by CFH is used to assess the quality of RS80 radiosonde humidity data. The difference of RS80 radiosonde humidity data in day and night time respectively compared to CFH data is also given in individual inter-comparison. The results have revealed there is a large dry bias produced by the RS80 humidity sensor with average of (23.7±18.5)%, and the daytime dry bias is (13.5±14.8)% larger than that in the nighttime owing to solar radiation heating on the humidity sensor. In addition, RS80 radiosonde is almost incapable of measuring the valuable humidity data in the transition region from upper troposphere to lower stratosphere. For the integrated precipitable water (PW) amounts from the profiles of GTS1, RS80, CFH and their comparisons with GPS measurements, CFH integrated PW is (4.3±2.0) mm (number of samples is 11) higher than that of GPS because that CFH tends to be saturation at moist condition, especially when passes through cloud in lower troposphere, while the PW differences of RS80, GTS1 from the GPS measurements are (0.2±1.4) mm (number of samples is 12) and (-0.2±2.2) mm (number of samples is 43) respectively. The value of GPS PW is not sensitive to the humidity variations in the altitudes above upper troposphere. CFH is demonstrated as an effective instrument measuring water vapor concentration in the circumstance with lower temperature as well as lower humidity, such as in the upper troposphere and lower stratosphere. Owing to dry bias, RS80 radiosonde detects less middle or high clouds than CFH does, especially in the detection of high clouds above 6000 m where the low humidity value from RS80 radiosonde almost cannot indicate the occurrence of cloud. Therefore, the occurrence frequency and altitude of high cloud would be much underestimated if RS80 radiosonde water profiles are used.