A statistical measure of severity of Ei Nino events

El Nino exerts a significant influence on climate, and hence tremendously a ffects human activities. The monthly Southern Oscillation Index (SOI) is us ed to quantify El Nino events. The severity of El Nino is determined by a c ombination of its maximum intensity, magnitude, and duration that may be mu tually correlated. However, the past analyses on the statistical properties of Ei Nino events either only take into account their occurrences or nonoc currences, or simply rank El Nino events by a few categories such as most s evere, severe, and less severe. Apparently, these analyses can not give a c omplete description of El Nino events. This article sheds new light on the statistical properties of El Nino events. The Gumbel logistic model, a biva riate extreme value distribution with Gumbel marginals is employed to analy ze joint probability distributions of El Nino maximum intensity and magnitu de, El Nino magnitude and duration, as well as El Nino maximum intensity an d duration. Based on the marginal distributions of El Nino maximum intensit y, magnitude, and duration, the joint distributions, conditional distributi ons, and associated return periods of two Of these El Nino characteristics can be readily obtained. Results indicate that statistics of El Nino events can be represented by the proposed method. The proposed method provides a much more detailed description of the properties of El Nino events than do the past approaches. It is also prior to single-variable frequency analysis .