Evaluation of the ERA-40 Surface Water Budget and Surface Temperature for the Mackenzie River Basin

Abstract

Abstract The systematic biases in temperature and precipitation, and the surface water budget of European Centre for Medium-Range Weather Forecasts (ECMWF) 40-yr reanalysis (ERA-40) for the Mackenzie River basin are assessed by comparing monthly averages from ERA-40 with basin averages of surface observations of temperature, precipitation, evaporation, and streamflow from the Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS). The bias and spinup of precipitation in ERA-40 changes significantly over the analysis period. On an annual basis, both precipitation bias and spinup are correlated with the analysis increment of atmospheric total column water vapor. ERA-40 has, in addition, a high bias of precipitation in spring and a low bias in fall. The monthly precipitation analysis is best for the most recent decade, when the bias of the 0–12-h forecast precipitation is only a few percent higher than the MAGS observations, and ERA-40 represents rather well the variability of monthly precip...