Estimation of daily mean air temperature from MODIS LST in Alpine area

This study is aimed at demonstrating the feasibility of the MODIS Land Surface Temperature (LST) product as a source for calculating spatially distributed daily mean air temperature to be used as input for hydrological or environmental models. The test area is located in the Italian Alpine area. The proposed procedure solves, by empirical approaches, the problem of relating LST to the Air Temperature (Tair) and instantaneous Tair values to daily mean values, exploiting ground data weather station measurements as a reference. The relationship between LST and Tair is deter-mined by correlation analysis and equation generalisation for spatial distribution. The extrapolation of daily mean values of Tair from instantaneous values is addressed again by correlation analyses taking into account the altitude variability and exploiting historical series. Validation was accom-plished by accuracy assessment procedures both punctual and spatially distributed, the latter per-formed by comparison with the Inverse Distance Weighting (IDW) interpolation method. The proposed methodology produced satisfactory results as related to the objective: The daily mean air temperatures derived by LST showing an overall RMSE of 1.89°C, and slightly outper-forms the interpolation method used as comparison.