Retrieval of precipitable water using special sensor microwave/temperature-2 (SSM/T-2) millimeter-wave radiometric measurements

Abstract

Four years of Special Sensor Microwave/Temperature-2 (SSM/T-2) measurements over the high-latitude regions of both the Northern and Southern Hemispheres are used to retrieve precipitable water W < 0.8 cm. The retrieved W values compare well with several thousand near-concurrent radiosonde-derived estimates of W. Additionally, very good agreement is found between the retrieved SSM/T-2 W values and continuous ground-based radiometer-derived estimates of W during a couple of extended time periods. A bias (0.03-0.06 cm) exists between the W values retrieved from the SSM/T-2 and the values derived from the radiosonde/radiometer observations. This bias is caused primarily by the assumption of equivalent surface emissivity across the 150-183 GHz frequency range that is made during the development of the retrieval algorithm. The spatial distribution of the SSM/T-2-retrieved winter mean W values is examined together with digital elevation models for both the Greenland and Antarctic ice sheets. This detailed comparison conveys expected climatological characteristics that are quite sensible when the combined effects of the surface elevation and the general atmospheric circulation patterns near and over the ice sheets are considered in unison. The SSM/T-2 W retrieval presented provides accurate W information with a high sampling rate for the potentially climate change-sensitive polar regions of the Northern and Southern Hemispheres.