Characterization of Extreme Rainfall Events Classes in the Tropical Andes by Using Weather Radar Data

Extreme rainfall is characterized by a high spatio-temporal variability. This variability is exacerbated in mountain areas, such as the tropical Andes, where the complex orography and mesoscale atmospheric processes have an enormous influence on the rainfall processes. Particularly the analysis of extreme rainfall events in the Ecuadorian Andes has remained a challenge due the lack of high spatio-temporal resolution operational observing systems. However, the recent availability of rainfall radar data in this area enables an improvement of our knowledge about those extremes. Here, we presented a study that aims to identify specific types of extreme rainfall events based on a clustering approach and to analyze their spatio-temporal characteristics. The study is based on three years of data collected from an X-band scanning weather radar that was located at 4450 m a.s.l in the Tropical Andes of southern Ecuador, delivering high resolution (5min, 500m) data. Several extreme rainfall events were identified, which were selected based on a rainfall accumulation threshold and visual inspection. Then, extreme rainfall events characteristics (e.g., rain rate, duration, rainfall accumulation, hour and month of occurrence) were identified for each event. Then, the k-means clustering was applied to the events using their rainfall characteristics. The main idea of this algorithm is to cluster a set of objects by accounting for their similarities. In our presentation, we will show the three major types of extreme rainfall events resulting from our analysis as well as the marked differences in their rainfall characteristics. The first type of extreme-events showed the highest values of intensity and the lowest values of duration. Also, two extreme-events types showed predominant months and hours of occurrence. In addition, the site of occurrence of the spatial nucleus of maximum intensity of the first type was located at higher elevations. We will show that the typology of extreme rainfall events improves our knowledge about the spatio-temporal characteristics in the tropical Andes.