Climate change projections for Catalonia (NE Iberian Peninsula). Part I: Regional climate modeling

This work presents a dynamical technique of climate downscaling to generate projections for the 21st Century in Catalonia, based on the outputs of the atmosphere-ocean global coupled model ECHAM5/MPI-OM. This technique consists in long integrations (5 years) with the MM5 mesoscalar model through three one-way nested domains of 135, 45 and 15 km of horizontal resolution and 23 vertical levels. Two possible emission scenarios of the Special Report on Emissions Scenarios are used for the generation of downscaled projections: a severe one (A2) and a moderate one (B1). Only temperature at 2 m and precipitation are studied in detail, as they are the variables of greatest social interest and the ones that condition the water resources most directly. The general space-time characteristics of these two variables are correctly reproduced by the methodology used, except for the seasonal cycle of precipitation. The simulations performed show a significant cold bias for temperature, as well as a general overestimation of precipitation. The scenarios obtained project a sharp increase of temperature (up to 5ºC at the end of the century) and a decrease in the annual mean precipitation during this century, but with a high spatial and temporal variability. This decrease is sharper during the warm period of the year (50% in some areas for summer at the end of the century). On the other hand, a slight increase is projected for the greater part of the cold period of the year. Regarding extreme values, a significant increase of warm months and a slight decrease of cold months is expected. About precipitation, a significant increase of dry periods is projected. However, an increase of extremely rainy months is also predicted. The projected changes are more marked for the A2 scenario than for B1.