Raman Lidar Calibration for the DMSP SSM/T-2 Microwave Water Vapor Sensor

摘要

Campaigns were conducted at the Pacific Missile Range Facility, Barking Sands, Kauai, investigating Raman lidar as a method to improve calibration of the DMSP SSM/T-2 microwave water vapor profiling instrument. Lidar mixing ratios were calibrated against AIR and Vaisala radiosondes and the calibration was tested in the vicinity of clouds. Above 6 km, radiosondes reported anomalously low relative humidity in the vicinity of clouds. Lidar measurements were confirmed by using an electro-optical shutter, which provided correct measurement of relative humidity at cloud bases above 6 km. Radiative transfer calculations applied to the lidar data closely matched signals observed in the SSM/T-2 atmospheric channels. Forward calculations for surface sensitive channels disagreed with SSM/T-22 and SSM/I observations. Fine scale surface roughness and localized orographic drying are tentatively suggested as explanations. Cloud effects were ruled out as a significant source of discrepancy.