A Study of Precipitation Climatology and Its Variability over Europe Using an Advanced Regional Model (WRF)

In recent years long-term precipitation trends on a regional scale have been given emphasis dueto the impacts of global warming on regional hydrology. In this study, regional precipitationtrends are simulated over the Europe continent for a 60-year period in 1950-2010 using an advancedregional model, WRF, to study extreme precipitation events over Europe. The model runscontinuously for each year during the period at a horizontal resolution of 25 km with initial/boundary conditions derived from the National Center for Environmental Prediction (NCEP) 2.5degree reanalysis data sets. The E-OBS 0.25 degree rainfall observation analysis is used for modelvalidation. Results indicate that the model could reproduce the spatial annual rainfall patternover Europe with low amounts (250 - 750 mm) in Iberian Peninsula, moderate to large amounts(750 - 1500 mm) in central, eastern and northeastern parts of Europe and extremely heavy falls(1500 - 2000 mm) in hilly areas of Alps with a slight overestimation in Alps and underestimationin other parts of Europe. The regional model integrations showed increasing errors (mean absoluteerrors) and decreasing correlations with increasing time scale (daily to seasonal). Rainfall issimulated relatively better in Iberian Peninsula, northwest and central parts of Europe. A largespatial variability with the highest number of wet days over eastern, central Europe and Alps(~200 days/year) and less number of wet days over Iberian Peninsula (≤150 days/year) is alsofound in agreement with observations. The model could simulate the spatial rainfall climate variabilityreasonably well with low rainfall days (1 - 10 mm/days) in almost all zones, heavy rainfallevents in western, northern, southeastern hilly and coastal zones and extremely heavy rainfallevents in northern coastal zones. An increasing trend of heavy rainfall in central, southern andsoutheastern parts, a decreasing trend in Iberian Peninsula and a steady trend in other zones arefound. Overall, the simulated rainfall climatology was reproduced well for the low and heavy rainfall followed by very heavy and extremely heavy rainfall in Europe and the simulation is betterin the Iberian west coast, central northern Europe and Alps Mountains