Spatial interpolation of air temperature according to atmospheric circulation patterns in southeast France

A method is proposed for the interpolation of daily maximum and minimum air temperatures (T-x and T-n, respectively) at the regional scale, taking int o account the atmospheric circulation patterns (CPs). The study region was in southeast France (150 x 250 km(2)). Daily temperatures measured at 152 m eteorological stations were available, and CPs from automatic classificatio n performed every day by Meteo France from forecast model outputs were used . For the whole of Europe, ten classes centred on France are defined. A geo statistical approach (ordinary kriging) was chosen, because it permits the mapping of the estimation variance for interpolation and consideration of s everal days at once. Different data processing methods were compared: raw t emperatures without correction; temperatures converted to sea level by appl ying a constant or varying coefficient according to the CP; and sorting day s in relation to CP and season. Cross-validation analyses were performed, s eparating the data set in two independent parts (62 stations for the model calibration and 90 for the validation). These sets of data showed errors fr om 0.6 degrees to 2 degrees C. An improvement of 0.5 degrees C was observed for the maximum temperature if it was corrected with regard to the elevati on and the days sorted according to CP; however, correction of the elevatio n had a greater effect on improving the results than does CP sorting. The r esults obtained for the minimum temperatures fluctuate more from day to day . Copyright (C) 1999 Royal Meteorological Society.