Regional modeling of dry spells over the Iberian Peninsula for present climate and climate change conditions

One of the major tasks of climate models is the description of precipitation characteristics. Many complex physical mechanisms are involved, and the corresponding parameterizations lead to more important differences among models for both present climate and climate change conditions than what is obtained for temperature analysis. Extreme precipitation events are more scarce, and therefore, differences are even larger. These processes are very relevant for impact studies, both when dealing with heavy precipitation events and also with drought conditions or dry spell description. But studies focused on dry spell analysis have received much less attention, compared with the ones related to large precipitation conditions. Present climate conditions already indicate important risks related to aridity over many areas of the world, and they are projected to be increased for future climate conditions. One good example of a region with these kind of risks is the Iberian Peninsula, where agricultural and socioeconomic impacts of water supply deficits are already a very relevant feature. The modeling results indicate that future climate will increase the mean and largest dry periods over most of the Iberian Peninsula, with a gradient of increase that is larger on the south and smaller on the north, therefore increasing the latitudinal contrast with respect to present climate. Regional features over certain basins and coasts are reproduced by the regional models, but not for the global climate model. Thus, future climate conditions point to a more severe hydrological stresses over several regions in the Iberian Peninsula.