Application of cluster analysis techniques to the verification of quantitative precipitation forecasts

The results of the verification of precipitation forecasts are highly affected by the distribution of rain gauges, and depend mostly on the model performance in areas where the gauges network is denser. For model verification purposes, in the present work the whole set of available measurements is divided into a series of geographical subsets, each of them displaying a similar precipitation pattern. Cluster analysis is adopted as an objective method to create groups of rain gauges displaying interrelated measurements. Clusters display a well defined spatial structure, related to the interaction of air masses with orographic obstacles. Verification scores computed in each cluster help in detecting the spatial variation of a model's performance.