Calibrating and evaluating reanalysis surface temperature error by topographic correction

Based on the observed daily surface air temperature data from 597 stations over continental China and two sets of reanalysis data [NCEP-NCAR and 40-yr ECMWF Re-Analysis (ERA-40)] during 1979-2001, the altitude effects in calibrating and evaluating reanalyzed surface temperature errors are studied. The results indicate that the accuracy of interpolated surface temperature from the reanalyzed gridpoint value or the station observations depends much on the altitudes of original data. Bias of interpolated temperature is usually in proportion to the increase of local elevation and topographical complexity. Notable improvements of interpolated surface temperature have been achieved through "topographic correction," especially for ERA-40, which highlights the necessity of removal of "elevation-induced bias" when using and evaluating reanalyzed surface temperature.