Daily atmospheric circulation events and extreme precipitation risk in northeast Spain: Role of the North Atlantic Oscillation, the Western Mediterranean Oscillation, and the Mediterranean Oscillation

Abstract

The definitive version is available at: http://www.agu.org/journals/jgr ; We used a novel method that combined probabilistic analysis and spatial modeling assisted by GIS to analyze the risk of extreme precipitation in northeast Spain related to three atmospheric circulation configurations: the North Atlantic Oscillation (NAO), the Mediterranean Oscillation, and the Western Mediterranean Oscillation (WeMO). The analysis was performed at an event-based scale using data obtained from daily atmospheric circulation indices. The maximum intensity and total precipitation magnitude recorded during positive and negative circulation events were obtained from the daily records of 174 observatories between 1950 and 2006. The series of both maximum intensity and magnitude for positive and negative phases of the three atmospheric circulation indices follow a generalized Pareto (GP) distribution. A regression-based interpolation procedure was used to generate distributed maps of GP parameters, enabling us to determine the probability of the magnitude and maximum intensity of precipitation and the quantile precipitation for any return period associated with the positive and negative phases of the three atmospheric circulation patterns. A high spatial variability in precipitation risk was found, depending on the positive/negative phases of the three atmospheric circulation patterns. Different phases of the circulation indices show contrasting effects on the two analyzed parameters. Thus the most extreme daily precipitation during winter months is expected for negative WeMO events, representing a markedly different result from those obtained for other events. In contrast, negative NAO events record the most extreme precipitation magnitude risk per event, although this is mainly restricted to mountainous areas. ; This work was supported by projects financed by the Spanish Commission of Science and Technology (CGL2005–04508/BOS and CGL2008–01189/BTE), the 7th framework program of the European Commission (projects ACQWA (FP7-ENV-2007-1-212250) and EUROGEOSS (FP7-ENV-2008-1-226487)), and the "Programa de grupos de investigación consolidados" financed by the Aragón Government. ; Peer reviewed