Comparison of model and satellite-derived long-term precipitation databases over the Mediterranean basin: A general overview

The knowledge of the Mediterranean basin hydrological cycle constitutes an issue with important implications in such a sensitive area. Precipitation is the best-known term of the Mediterranean budget, although large uncertainties remain. The major methodological drawback for its long-term assessment comes from the lack of suitable offshore observational data. This fact has driven towards the use of model-derived products to make estimations of precipitation and its variability over sea. In this scenario, satellite-based products arise as useful tools to assess the Mediterranean precipitation regime and, in spite of their known limitations, to evaluate different available model datasets. This work identifies existing similarities over the Mediterranean between five precipitation monthly means data sets derived from global reanalyses (NCEP and ERA40), regional hindcasts (HIPOCAS and ARPERA) and satellite-derived products (GPCP version 2) for the 22-year period encompassing 1979 through 2000.Whereas all the databases reproduce a latitudinal gradient, HIPOCAS, NCEP and ERA40 present precipitation values lower than GPCPv2, unlike ARPERA, which slightly overestimates the satellite-derived estimations. Time correlations and a wavelet analysis indicate a good degree of similarity between simulated and observational data sets regarding time evolution and variability.Considering the performed validations together with the limited time coverage of satellite-derived data, HIPOCAS, ARPERA and ERA40 products arise as adequate tools to carry out long-term climate precipitation studies over the Mediterranean basin and particularly over its offshore areas, unlike NCEP, which seems less consistent over this area.