SIMULTANEOUS MEASUREMENTS OF ATMOSPHERIC WATER-VAPOR WITH MIR, RAMAN LIDAR, AND RAWINSONDES

Simultaneous measurements of atmospheric water vapor were made by the Millimeter-wave Imaging Radiometer (MIR), Raman lidar, and rawinsondes . Two types of rawinsonde sensor packages (AIR and Vaisala) were carri ed by the same balloon. The measured water vapor profiles from Raman l idar, and the Vaisala and AIR sondes were used in the radiative transf er calculations. The calculated brightness temperatures were compared with those measured from the MIR at all six frequencies (89, 150, 183. 3 +/- 1, 183.3 +/- 3, 183.3 +/- 7, and 220 GHz). The results show that the MIR-measured brightness temperatures agree well (within +/-2 K) w ith those calculated from the Raman lidar and Vaisala measurements. Th e brightness temperatures calculated from the AIR sondes differ from t he MIR measurements by as much as 10 K, which can be attributed to low sensitivity of the AIR sondes at relative humidity less than 20%. Bot h calculated and the MIR-measured brightness temperatures were also us ed to retrieve water vapor profiles. These retrieved profiles were com pared with those measured by the Raman lidar and rawinsondes. The resu lts of these comparisons suggest that the MIR can measure the brightne ss of a target to an accuracy of at most +/-2 K and is capable of retr ieving useful water vapor profiles.