An overview of passive microwave snow research and results

Abstract

The current state of knowledge of the microwave properties of snow is discussed. Theory behind the microwave emission from snow is reviewed, as are the physical processes of snowpack metamorphism. Field, aircraft, and satellite passive microwave data have been acquired and analyzed for more than 10 years. Results have repeatedly demonstrated the feasibility of employing multifrequency passive microwave data to study snow‐covered area, snow depth, and internal snowpack properties. Radiation emanating from the ground beneath a snowpack is scattered by the snow crystals, and concurrently, the snow itself emits radiation at microwave frequencies. Thus the radiation emerging from the snowpack is the result of a complex series of interactions both within and beneath the snowpack. Future studies recommended by a snowpack properties working group consisting of government and university scientists are discussed in detail. Recommendations include performing extensive laboratory measurements using real and artificial snow, to be coordinated with theoretical modeling and aircraft overflights carrying passive microwave instrumentation. This is considered necessary in order to help to interpret the microwave responses to snow.

Effects of Forest on the Snow Parameters Derived From Microwave Measurements During the Boreas Winter Field Campaign

“…The deeper the snowpack, the more crystals are available to scatter microwave energy away from the sensor. Hence, microwave brightness temperatures are generally colder, or lower, for deep snowpacks than they are for shallow snowpacks (Foster et al, 1984). Drawbacks of the microwave approach include poor resolution and difficulty in interpreting the effects of snow structure on microwave response and in understanding microwave emission and interaction with other media (Hall et al, 1985(Hall et al, , 1991.…”

Review of Science Issues, Deployment Strategy, and Status for the ARM North Slope of Alaska–Adjacent Arctic Ocean Climate Research Site

“…For example, assessments of snow extent, derived from the National Oceanic and Atmospheric Administration (NOAA) visible and near-infrared imagery under cloud-free conditions, have been available for 25 yr (e.g., Kukla and Kukla 1974;Matson et al 1986;Robinson et al 1993). Likewise, passive microwave sensors have proven useful for monitoring snow extent and water equivalent, through cloud cover and darkness (Rango et al 1979;Kunzi et al 1982;Foster et al 1984;Goodison et al 1986;Chang et al 1987), although there are problems related to the detection of thin dry snow (producing insufficient signal to differentiate it from the underlying surface), and shallow wet snow (having an emittance similar to bare, wet ground).…”

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

“…Passive microwave sensors which sense the emitted radiation can provide information regarding the internal characteristics of snow and ice (Chang and others, 1976). Previous studies have shown that there is an inverse relationship between snow depth and microwave TB as measured by passive microwave sensors at specified wavelengths in dry snow (Foster and others, 1984). The 37 GHz (0.81 cm wavelength) sensor of the Scanning Multichannel Microwave Radiometer (SMMR) on board the Nimbus-7 satellite has been shown to be particularly useful for analyzing internal properties of snow-packs especially when the horizontally polarized data are used (Hall and others, 1984).…”