Evaluation of ERA-Interim and ERA-Interim-GPCP-rescaled precipitation over the U.S.A.
Balsamo, G. ; Bousetta, S. ; Lopez, P. ; Ferranti, L.
A 3-hourly global precipitation dataset extracted from the European Centre for Medium range Weather Forecasts (ECMWF) - Interim Reanalysis (ERA-Interim) is validated against different precipitation datasets and accumulation periods over the U.S.A.: the Global Precipitation Climatology Project - Global Monthly Merged Precipitation Analysis (GPCP v2.0 and v2.1), the U.S.A. Department of Agriculture (USDA) official precipitation climatology (PRISM) for annual and monthly accumulations and the National Centers for Environmental Prediction precipitation dataset (NCEP Stage IV) for daily amounts. The results show that, over the U.S.A., the ERA-Interim precipitation has comparable quality to GPCP v2.1 for annual averages and a spatial correlation of 0.85 with respect to the PRISM dataset (2000-2008). A scale-selective rescaling procedure is also proposed to re-calibrate the ERA-Interim reanalysis with GPCP product. The annual spatial correlation of ERA-Interim-GPCP-rescaled precipitation versus PRISM increases up to 0.90. Benefits of the rescaling method are confirmed also at monthly and daily time-scales.
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