Downscaling ERA-Interim temperature data in complex terrain

Abstract. Air temperature controls a large variety of environmental processes, and is an essential input parameter for land surface models e.g. in hydrology, ecology and climatology. However, meteorological networks, which can provide the necessary information, are commonly sparse in complex terrains, especially in high mountainous regions. In order to provide temperature data in an adequate temporal and spatial resolution for local scale applications, we have developed a new downscaling method able to scale 3-hourly ERA-Interim temperature data. The scheme is based on model internal vertical lapse rates derived from different ERA-Interim pressure levels. The results are validated for three meteorological stations, located within the same ERA-Interim grid element: Zugspitze, Garmisch-Partenkirchen and Zugspitzplatt, in the German Alps; they are also compared with two other statistical, lapse rate based downscaling approaches. The results indicate that the use of model internal ERA-Interim lapse rates can significantly improve the downscaling performance when compared to the standard procedure of using fixed lapse rates.