WATER-VAPOR PROFILING OVER OCEAN SURFACE FROM AIRBORNE 90 AND 183 GHZRADIOMETRIC MEASUREMENTS UNDER CLEAR AND CLOUDY CONDITIONS

Radiometric measurements at 90 GHz and three sideband frequencies near the water vapor absorption Line of 183.3 GHz were made with the advan ced microwave moisture sounder (AMMS) aboard the NASA DC-8 aircraft ov er some regions of the Pacific Ocean during November 1989. These measu rements were used to retrieve atmospheric water vapor profiles over oc ean surface using the algorithm developed by Wilheit. The algorithm in corporates a mechanism to estimate cloud liquid water when the estimat ed relative humidity is greater than 95%. The results were compared wi th the estimated values from the measurements of special sensor microw ave imager (SSMI) and TIROS operational vertical sounder (TOVS). The w ater vapor profiles estimated from AMMS are generally higher at low al titudes and lower at high altitudes compared to those from the TOVS me asurements. Values of total precipitable water estimated from the AMMS and SSM/I are in general agreement. Cloud liquid water is retrieved f rom both AMMS and SSM/I measurements over the same general regions. Th e water vapor profiles retrieved from the AMMS show more fluctuations in these regions; frequently, there is a deficiency of water vapor at low altitudes. Most likely, the AMMS with only four channels of measur ements cannot retrieve both water vapor and cloud information with aut hority.