Temporal analysis (1940-2010) of rainfall aggressiveness in the Iberian Peninsula basins

- We have studied the rainfall aggressiveness index in the Spanish river basins.
- The modified Fournier and precipitation concentration indices have been used jointly.
- The evolution of the different basins between 1940 and 2010 have been shown.
- Behaviours linked to the Atlantic and Mediterranean influence have been identified.

Rainfall aggressiveness causes environmental impacts and it is related to several natural hazards. Therefore, this parameter has been chosen as an environmental indicator. The present study is based on the monthly estimated rainfall using the Precipitation Runoff Integrated Model (SIMPA) for each Spanish hydrographic basin from 1940 to 2010. The main aim is to analyse temporal irregularity of rainfall aggressiveness in large geographic areas and to extract spatio-temporal patterns. For each year the rainfall aggressiveness was calculated using the Modified Fournier Index (IFM) and Oliver's Index of Precipitation Concentration (IPC). The temporal variability of the annual series of these indices was analysed for each zone delimited. The results obtained made it possible to characterize the rainfall aggressiveness in the Iberian Peninsula and to determine its evolution over the past decades. They also reveal that the general pattern of the rainfall aggressiveness is determined by the dual effect of latitude (north-south) and longitude (east-west) as a result of the different maritime influences of the Atlantic and the Mediterranean watersheds. Finally a new variable is proposed, the Annual Aggressiveness Risk RA, which summarizes the information provided by IFM and IPC.