Special Sensor Microwave/Imager (SSM/I)

Snow Cover/Sea Ice

Overview

1. Snow Cover

Snow cover also exhibits scattering characteristics similar to precipitation, and can be detected by using brightness temperature differences between low frequency measurements (e.g. 19 or 22 Ghz) and higher frequency measurements (e.g. 37 or 85 GHz), the latter of which are scattered by the snow grains. Rain and snow can usually be separated by examining the physical temperature of the surface.

The SSM/I snow cover product is being used as part of the operational NOAA/NESDIS daily snow product (NESDIS Daily Snow Analysis). The SSM/I technique is objective and its main advantage over visible imagery is its ability to produce retrievals through clouds. Thus, it makes the perfect compliment.

2. Sea-Ice

The detection of sea-ice by passive microwave measurements utilizes low frequency measurements to detect surface emissivity of the ocean surface. Sea-ice possesses a higher emissivity than water, and hence, the two can be separated. Care must be taken to avoid false signatures caused by dense clouds and precipitation.

References

Basist, A., D. Garrett, R. Ferraro, N.C. Grody, and K. Mitchell, 1996: A comparison between visible and Microwave snow cover products derived from satellite observations. J.Appl.Meteor., 35, 163-177.

Ferraro, R.R., N.C. Grody, and G.F. Marks, 1994: Effects of surface conditions on rain identification using the SSM/I, Rem. Sens. Rev., 11, 195-209.

Grody, N.C., 1991: Classification of snow cover and precipitation using the Special Sensor Microwave/Imager (SSM/I). J. of Geophys. Res., 96, 7423-7435.

Grody, N.C. and A. Basist, 1996: Global identification of snow cover using SSM/I measurements. IEEE Trans. Geosci. and Rem. Sens., 34, 237-249.

Grody, N.C. and A. Basist, 1997: Interpretation of SSM/I measurements over Greenland. IEEE Trans. Geosci. Rem. Sens., 35, 360-366.