GLOBAL FORTY-YEARS VALIDATION OF SEASONAL PRECIPITATION FORECASTS: ASSESSING EL NIÑO-DRIVEN SKILL

Abstract. The skill of seasonal precipitation forecasts is assessed worldwide —grid point by grid point — for the forty-years period 1961-2000. To this aim, the ENSEMBLES multi-model hindcast is considered. Although predictability varies with region, season and lead-time, results indicate that 1) significant skill is mainly located in the tropics —20 to 40% of the total land areas—, 2) overall, SON (MAM) is the most (less) skillful season and 3) predictability does not decrease noticeably from one to four months lead-time —this is so especially in northern south America and the Malay archipelago, which seem to be the most skillful regions of the world—. An analysis of teleconnections revealed that most of the skillful zones exhibit significant teleconnections with El Niño. Furthermore, mod-els are shown to reproduce similar teleconnection patterns to those observed, especially in SON —with spatial correlations of around 0.6 in the tropics—. Moreover, these cor-relations are systematically higher for the skillful areas. Our results indicate that the skill found might be determined to a great extent by the models ’ ability to properly repro-duce the observed El Niño teleconnections, i.e., the better a model simulates the El Niño teleconnections, the higher its performance is. 1