Passive microwave images of the polar regions and research applications

Abstract

Passive microwave images of the polar regions, first produced after the launch of the Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR)in December 1972, have become a valuable new source of polar information. Some of the potential applications of this new capability were anticipated. Of these, the sensing of sea ice through clouds and the polar night is probably the most important application for polar research and for operations on the polar seas. Other applications, such as the measurement of certain near-surfaceice sheet parameters, have been formulated more recently. Measurement of various ocean surface parameters is expected from the forthcoming multifrequency microwave observations. Undoubtedly additional uses of passive microwave datawill be conceived and developed. Two remarkable aspects of satellite-borne microwave radiometers are the complete spatial detail obtained by the scanning sensors and the temporal detail provided by continual coverage. For example, the observations of detailed microwave emission patterns over the Antarctic ice sheet should yield information that could not be obtained by surface or even aircraft measurements. Sequences of images produced at three-day intervalsreveal short-term ice sheet and sea ice phenomena that would otherwise be missed.

Review article "A. B. Dobrowolski – the first cryospheric scientist – and the subsequent development of cryospheric science"

“…This evolution depended heavily on the advent of satellite remote sensing using optical sensors on NOAA platforms from 1966 and Landsat from 1972. In Hall and Martinec's (1985) book on remote sensing of snow and ice the emphasis is still on basins and regional scale features, but passive microwave data allowed the first hemispheric, all-weather, yearround views of polar sea ice (Zwally and Gloersen, 1977) and this hemispheric scale approach was later extended to all cryospheric components. Global remote sensing involving all spectral wavelengths is now a mainstay of cryospheric research especially in polar and mountain regions where access is difficult (Thomas, 1991).…”

Springtime microwave emissivity changes in the southern Kara Sea

“…Since the skin depth for dry snow (in the SMMR frequency range) is of the order of 0.5 to 2.0 m, it is usually assumed that except for an unusually thick snow cover or during the melt season, snow will have little effect on the brightness temperature over sea ice [Zwally and Gloersen, 1977;Chang et al, 1976Chang et al, , 1982. During melt, however, several changes occur that do influence the emissivity.…”

Detection of the Depth-Hoar Layer in the Snow-Pack of the Arctic Coastal Plain of Alaska, U.S.A., Using Satellite Data

“…Observation and modeling have shown that differences in emissivity are related to variations in snow accumulation rates, mean annual temperature, and melting effects on the ice sheets (Zwally and Gloersen, 1977). Specifically, larger grain-sizes in ice-sheet locations having low accumulation rates are known to cause more scattering and to be associated with lower microwave emissivities.…”