Satellites—New Global Observing Techniques for Ice and Snow

Abstract

Starting with the TIROS-2 Weather Satellite in 1961 which permitted synoptic viewing of large scale areas with an on-board television camera system, the capabilities of satellite observations for assessing snow and ice resources on earth have been greatly improved through the utilization of higher resolution imaging systems and multispectral images in the wavelength range from 0.4 micrometers to 1.55 cm. Possibilities that the variation in areal extent of the snow cover may be related by empirical means to the average monthly runoff in a given watershed were demonstrated by comparing runoff records from the Indus River Basin in Southeast Asia with a series of snowcover maps obtained from Nimbus 3 and 4 imagery. Similar studies using the higher spatial resolution available with ERTS-1 imagery were carried out for the Wind River Mountains watersheds in Wyoming, where it was found that the empirical relationship varied with mean elevation of the watershed. In addition, digital image enhancement techniques are shown to be useful for identifying glacier features thought to be related to extent of snowcover, moraine characteristics, debris average, and the like. Finally, longer wavelength observations using sensors on board the Nimbus 5 Satellite are shown to be useful for indicating crystal size distributions and onset of melting on glacier snow cover.iii

Passive microwave images of the polar regions and research applications

“…Firstly, snow or firn subjected to alternate melting and freezing has enhanced grain sizes and, thus, a lower emissivity-although its emissivity is low only when it is dry and not during the melt stages. Secondly, when the snow or firn becomes wet its emissivity increases markedly (Gloersen and Salomonson, 1975), because internal scattering is reduced by the thin film of water on the snow grains (Chang and Gloersen, 1975).…”

Assessment of Potential SSM/I (Special Sensor Microwave/Imager) Ice Products in Light of ESMR (Electrically Scanning Microwave Radiometer) and SMMR (Scanning Microwave Spectrometer) Ice Classification Algorithms

“…Overall accuracy for the model is estimated to be +6% for ice concentration greater than 35% (Gloersen, et al , 1974) and +10% or better overall (Gloersen and Salomonson, 1975). These estimates are not documented by ground truth data.…”

Satellite‐Based Remote Sensing

“…The first satellite observations of the sea surface temperature and sea ice were made using ESMR data from NIMBUS-5 (Table 6.1) (see for example Gloersen and Salomonson, 1975). Zwally and Gloersen (1977) provided impressive microwave images of the Antarctic and Arctic in both summer and winter.…”