Analysis of rainfall behavior and aggressiveness in the central zone of Chile.

Abstract

Temporal and spatial rainfall distribution were analyzed in the central zone of Chile in order to define the level of rainfall aggressiveness and concentration. Monthly and annual precipitation data from 63 rain gauge stations were used for calculating the Fournier Index (FI), the Fournier Modified Index (MFI) and the Maule-Fournier Modified index (IMFM); the latter one was created specially for this research. The Precipitation Concentration Index (PCI) was used for rainfall concentration. Results showed that rainfall aggressiveness on the Andes mountains is greater than on the other study sites. In addition, all indexes showed a direct relation with rainfall, meaning that an increase in the amount of rainfall equals to an increase in the aggressiveness level. Furthermore, the PCI index indicated that rainfall has not shown a temporary change in yearly concentration, and it was possible to verify that the central zone of Chile is highly seasonal. In this context, high variation coefficient values obtained by rainfall analysis and applied indexes show that this zone has a high climatic variability, which can be explained by the Mediterranean climate observed in this area. Finally, rainfall during the 2000-2004 period has shown a strongly increasing trend.