Combining circulation weather types and daily precipitation modelling to derive climatic precipitation regions in the Pyrenees

The Pyrenees is a mountain range that presents a very broad range of climatic diversity, as well as a multitude of geographical factors conditioning precipitation in this region. In-depth knowledge of this precipitation, specifically of its association with atmospheric circulation types in mountain regions, is of great importance for the management of natural hazards such as avalanches or floods. Thus, the present research combines the synoptic scale with the local scale. We employed the regional scale of the Pyrenees to interpolate, by means of the General Linear Models (GLM), General Additive Models (GAM) and Regression Kriging (RK) methods, mean daily precipitation (MDP) based upon a classification of weather types at the synoptic scale; this procedure reflects the most frequent atmospheric patterns in the study area during the 1961-2010 period. This combination of scales makes it possible to perform a spatial precipitation regionalization of the Pyrenees by means of the work flow proposed in the present research. The result is a compendium of 20 atmospheric circulation types. For each of these circulation types, we obtained MDP maps for each of the aforementioned interpolation methods. The most satisfactory fit of the models was provided by the GAM and the RK methods, with an average R-2 of all models of 0.58 and 0.61, respectively. These models provided a precipitation regionalization of the Pyrenees involving eight differentiated regions, two of which reveal a statistically significant annual tendency towards a decrease in precipitation.