Systematic errors in the simulation of european climate (1961-2000) with RegCM3 driven by NCEP/NCAR reanalysis

Systematic errors of a European climate simulation (1961-2000) with RegCM3 were analyzed. Model results were compared to Climate Research Unit (CRU) observations. Average (AveB) and annual cycle biases (CycB) were evaluated for three surface variables: air temperature (TMP), water vapor pressure (VAP), and precipitation (PRE). The model shows a cold AveB over Europe with the exception of the northern part. It also shows a prevailing wet AveB. Annual PRE is underestimated only in regions with high average values, while VAP is overestimated over the entire European continent. The AveB is between -1.2 degrees C and +1.0 degrees C for TMP, 0.4 mb and 1.4 mb for VAP and -15% and +33% for PRC on annual/subcontinental scale. Most of the TMP and VAP CycB is related to the amplitude of annual cycle (CycA). The CycA of the TMP is underestimated over most of Europe. The CycA of the VAP is underestimated in some coastal regions and overestimated over the continental regions. The distinction between coastal and inland regions can also be seen in the CycB of the PRE. In coastal regions, with a PRE maximum in late autumn/early winter and minimum in summer, the CycA is underestimated. In some continental regions, with a precipitation maximum in summer and minimum in late autumn/early winter, the CycA is overestimated. The annual cycle pattern is not captured well by RegCM3 over the Alps and European Russia. Most of systematic errors in the RegCM3 simulation can be related to boundary conditions. Although the bias in NCEP/NCAR reanalysis is reflected in RegCM3 simulation, the RegCM3 enriches large-scale information with regional details and with the more realistic description of annual cycles, especially for PRE. Because of these advantages and the overall relatively good performance of RegCM3, the model is seen as a valuable tool in regional projections of future climate change. Copyright (c) 2006 Royal Meteorological Society.