Daily atmospheric circulation events and extreme precipitation risk innortheast Spain: Role of the North Atlantic Oscillation, the WesternMediterranean Oscillation, and the Mediterranean Oscillation

摘要

We used a novel method that combined probabilistic analysis and spatial modelingassisted by GIS to analyze the risk of extreme precipitation in northeast Spain related tothree atmospheric circulation configurations: the North Atlantic Oscillation (NAO), theMediterranean Oscillation, and the Western Mediterranean Oscillation (WeMO). Theanalysis was performed at an event-based scale using data obtained from dailyatmospheric circulation indices. The maximum intensity and total precipitation magnituderecorded during positive and negative circulation events were obtained from the dailyrecords of 174 observatories between 1950 and 2006. The series of both maximumintensity and magnitude for positive and negative phases of the three atmosphericcirculation indices follow a generalized Pareto (GP) distribution. A regression-basedinterpolation procedure was used to generate distributed maps of GP parameters, enablingus to determine the probability of the magnitude and maximum intensity of precipitationand the quantile precipitation for any return period associated with the positive andnegative phases of the three atmospheric circulation patterns. A high spatial variability inprecipitation risk was found, depending on the positiveegative phases of the threeatmospheric circulation patterns. Different phases of the circulation indices showcontrasting effects on the two analyzed parameters. Thus the most extreme dailyprecipitation during winter months is expected for negative WeMO events, representing amarkedly different result from those obtained for other events. In contrast, negative NAOevents record the most extreme precipitation magnitude risk per event, although this ismainly restricted to mountainous areas.