Precipitation Scenarios over Iberia: A Comparison between Direct GCM Output and Different Downscaling Techniques

Abstract

The Iberian rainfall regime is characterized by a strong seasonal cycle and large interannual variability. Typically, frequency distributions of monthly precipitation present a large spread of values, implying frequent episodes of very wet or very dry years. Unfortunately, the most recent generation of general circulation models (GCMs) still has serious problems when modeling monthly precipitation over southern Europe. However, these models are able to reproduce the main patterns of atmospheric circulation, such as those derived from a principal component analysis of the sea level pressure anomaly field. Many downscaling techniques have been developed in recent years, all having in common the need to establish statistical links between the large-scale circulation and the observed precipitation at a local or regional scale. The final objective is usually the application of such transfer functions to GCM output. In this work, linear and nonlinear downscaling transfer functions are developed based o... Abstract The Iberian rainfall regime is characterized by a strong seasonal cycle and large interannual variability. Typically, frequency distributions of monthly precipitation present a large spread of values, implying frequent episodes of very wet or very dry years. Unfortunately, the most recent generation of general circulation models (GCMs) still has serious problems when modeling monthly precipitation over southern Europe. However, these models are able to reproduce the main patterns of atmospheric circulation, such as those derived from a principal component analysis of the sea level pressure anomaly field. Many downscaling techniques have been developed in recent years, all having in common the need to establish statistical links between the large-scale circulation and the observed precipitation at a local or regional scale. The final objective is usually the application of such transfer functions to GCM output. In this work, linear and nonlinear downscaling transfer functions are developed based o...