Spatial distribution of the air temperature in mountainous areas using satellite thermal infra-red data

Understanding the spatial distribution of air temperature in mountainous areas is essential in hydrological modelling. In the Moroccan High-Atlas range, the meteorological stations network is sparse. In order to get additional information, we investigated the thermal infrared data supplied by the Enhanced Thematic Mapper (ETM + ) sensor onboard the Landsat 7 satellite. The brightness temperature derived from ETM+ images is used as a proxy for air temperature to set up a model that describes its spatial distribution. This model accounts for sun location and topographic characteristics derived from the SRTM digital elevation model. It was evaluated on the Rheraya watershed, a 225-km2 region located within the semi-arid High-Atlas mountain range, using two different sources of data. The first data set consists in in-situ air temperature collected by meteorological stations installed during the experiment at various altitudes from 1400 to 3200 m. The second data set is satellite estimates of snow-covered areas (SCA) derived from MODIS images over the whole catchment at 500 m spatial resolution.