Atmospheric moisture measurements: a microwave radiometer-radiosonde comparison

The NASA/Goddard Space Flight Center Crustal Dynamics Project microwave Water Vapor Radiometer (WVR-J03) is used to measure the thermal emission of the sky at three frequencies (20.7, 22.2, and 31.4 GHz). Measurements were taken during the Atmospheric Moisture Intercomparison Study (ATMIS) held at Wallops Island, VA during April 1989. These measurements were compared with brightness temperatures inferred from measurements from VAISALA radiosonde packages launched every 3 h during the experiment period. An error analysis for the radiosonde-inferred brightness temperatures was performed, assuming reasonable random uncertainties for the pressure, temperature, and humidity measurements and propagating these uncertainties through the analysis algorithm. Two different water vapor emission models were used for the derivation of the brightness temperatures from the radiosonde measurements. Differences between the two models increase as the moisture content increases and vary as a function of frequency