High-resolution projections of mean and extreme precipitation over Spain using the WRF model (2070-2099 versus 1970-1999)

A set of eight simulations at high spatial resolution (10 km) were performed with WRF to generate future projections of mean and extreme precipitation over Spain. The model was driven with two GCMs (ECHAM5 and CCSM3.0) under the conditions of three SRES emissions scenarios (B1, A1B and A2) which amounts to six future (2070-2099) climate simulations. Two present (1970-1999) climate simulations forced by the same GCMs were previously completed and were used as a baseline to allow for comparison and quantify the changes. The annual and seasonal precipitation means were examined to elucidate how global warming will manifest in the future precipitation climatic means. The distribution of precipitation in different-intensity events and the percentiles were calculated to further describe the nature of the changes. Additionally, a number of extreme indices were explored to determine changes in the low frequency events and the persistency of specific conditions. The results indicate that Spain might be exposed to a substantial decrease in annual precipitation that range between -18% and -42% depending on the simulation, with a particularly severe reduction during the summer, between -32% and -72%. These changes are generally caused by less light-to-moderate events, which leads to a displacement of the probability density function toward higher values. Namely, future climate might be characterized by less precipitation but more concentrated in extreme events, although their occurrence in absolute terms might not vary. The projections also suggest that, by the end of the century, the wet periods might be shorter and the dry spells significantly longer.