Microwave brightness temperature as an indicator of near-surface air temperature over snow in Canadian northern regions |
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Authors: | Jacqueline Köhn |
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Affiliation: | CARTEL, Université de Sherbrooke , Sherbrooke , Québec , Canada |
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Abstract: | During the past 50 years, winter temperatures have risen more rapidly than in summer in northern high latitudes. However, there are relatively few meteorological stations in these areas, and a better characterization of this trend is needed. This article investigates whether satellite microwave brightness temperature can be used as an indicator of near-surface air temperature over snow. The Helsinki University of Technology (HUT) snow emission model is used to generate a dry snow emissivity relationship between 19 and 37 GHz under the assumption that the air–snow interface temperatures and air temperatures (Tair ) are similar. This relationship allows the development of a near-surface air temperature retrieval model. A second empirical linear correction is also applied to reduce the residual observed bias. The comparison between retrieved near-surface air temperature and in situ air temperature for the Canadian northern regions shows a significant correlation (R 2 of 0.76) but with a root mean square error (RMSE) of 4.94°C. Results also show that the satellite-derived temperatures can be compared to the thermal infrared skin temperature (RMSE of 5.9°C). The proposed approach gives better results than the direct correlation between brightness temperature (T b) and in situ air temperature (RMSE reduced by 50%). |
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