Airborne dual-channel radiometric ocean surface observations during SCOPE 93

The Environmental Technology Laboratory (ETL) has developed an aircraft-based dual-frequency microwave radiometer that can measure the upward or the downward radiance at 23.87 and 31.65 GHz. The radiometer´s antenna can be operated in a variety of operator-selected modes. It can be pointed upward continuously, point downward continuously, or alternate between upward- and downward-viewing modes. When viewing upward, the measured brightness temperatures can be processed to derive the water vapor and cloud liquid overburdens. Measurements of the spatial variability of these parameters can provide fundamental information for climate, cloud, and radiation studies. When viewing downward, the measured radiation consists of surface emissions, downward radiation reflected by the surface, and upward emissions from the intervening atmosphere. By flying the aircraft at various altitudes, and by alternately measuring the upward and downward emissions, the surface emissivity may be determined (the surface temperature is measured using an infrared radiometer). Such aircraft measurements, when coordinated with satellite overflights, can provide data to assist in the interpretation of satellite measured environmental parameters