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 (Tx and Tn, respectively) at the regional scale, taking into account the atmospheric circulation patterns (CPs). The study region was in southeast France (150×250 km). Daily temperatures measured at 152 meteorological stations were available, and CPs from automatic classification performed every day by Météo France from forecast model outputs were used. For the whole of Europe, ten classes centred on France are defined. A geostatistical approach (ordinary kriging) was chosen, because it permits the mapping of the estimation variance for interpolation and consideration of several days at once. Different data processing methods were compared: raw temperatures without correction; temperatures converted to sea level by applying a constant or varying coefficient according to the CP; and sorting days in relation to CP and season. Cross-validation analyses were performed, separating the data set in two independent parts (62 stations for the model calibration and 90 for the validation). These sets of data showed errors from 0.6° to 2°C. An improvement of 0.5°C was observed for the maximum temperature if it was corrected with regard to the elevation and the days sorted according to CP; however, correction of the elevation had a greater effect on improving the results than does CP sorting. The results obtained for the minimum temperatures fluctuate more from day to day. Copyright © 1999 Royal Meteorological Society.