Sar Remote Sensing of Snow Parameters in Norwegian Areas — Current Status and Future Perspective

Abstract

The paper present results from a series of European and national projects on remote sensing of snow parameters. Currently, satellite borne SAR data are only available at C-band frequencies. Other frequencies such as L-band or Ku-band may be favorable in several snow applications, but current C-band SAR may still be used and further developed to a more mature level. In particular, the advent of wide swath SAR data have provided frequent data sets at medium spatial resolution, that can be used to monitor snow parameters operationally.We will present results from a snow covered area monitoring service developed for Norway and Sweden. The service, which is based on Envisat ASAR wide swath data, produces snow cover maps on average 3–4 times per week. The resulting time series gives a unique data set for studying the snow cover as it rapidly retreats during the melting season, and is of high value to hydro power companies.Snow water equivalent is the key parameter for hydrological applications. Norut IT has developed a technique using repeat pass interferometry to measure SWE, based on the linear relationship between the change in SWE and the change in interferometric phase. The technique has been demonstrated, but scarceness of usable interferometric baseline pairs have so far not allowed wide spread applicability of the technique.A future SAR using Ku-band frequency as carrier will maybe solve the problem of retrieving SWE. Since backscatter at Ku-band frequency is more sensitive to SWE, it is good hope that robust SAR methods can be invented for this purpose. It will, however, be extremely important for the scientific community to validate the retrieval algorithms against in-situ data. The authors have developed an innovative validation concept using ground-penetrating radars at the same carrier frequencies as the space borne SARs to validate EO data in an efficient manner. The concept has been studied at C-band frequencies on glaciers at Svalbard, and we hope to build a similar platform for Ku-band frequencies, which will be used to validate model based retrieval algorithms.