Multifrequency microwave radiometry of snow on lake ice: Observations and simulations

We have conducted airborne multi-frequency radiometer measurements over two lakes and adjacent land areas in southern Finland over a period of several winters using a frequency range of 1.4 to 36.5 GHz. Data have been collected under a variety of snow, ice, and weather conditions in order to determine the behavior of the snow-ice-water system. This paper presents an overview of the airborne campaigns and results confirming that the brightness temperature behavior of the snow/lake ice/water system is different from that of the snow/terrain system. This needs to be taken into account in algorithms for retrieval of snow characteristics from space-borne radiometer data for northern lake-rich areas. Comparisons between experimental brightness temperatures and theoretical results show that the HUT snow emission model performs well for lake ice.

1. Introduction

Microwave radiometry is a well-established technique for retrieval of the water equivalent of dry snow cover from space. Regional algorithms have been developed and validated for this purpose [1], usually employing 36 and 18 GHz frequencies. However, for northern lake-rich areas, where lakes may cover up to 20 % of the region, retrieval accuracy may be decreased, because the emission behavior of the snow/lake ice/water system is different from that of the snow/terrain system. On top of lake ice, snow depth and snow grain size may substantially differ from those on land and, additionally, the emission characteristics of the ice/water system are different from those of soil [2], [3].