Evolution of El Niño-precipitation relationships from satellites and gauges

Abstract

This study uses a 23 year (1979-2001) satellite-gauge merged community data set to further describe the relationship between El Niño-Southern Oscillation (ENSO) and precipitation. The globally complete precipitation fields reveal coherent bands of anomalies that extend from the tropics to the polar regions. El Niño-precipitation relationships were analyzed during the six strongest events from 1979 to 2001. El Niños were defined based on the zonal contrast in rainfall in the equatorial Pacific, and seasons of precipitation evolution (pre-onset, onset, peak, decay, and postdecay) were identified. Areas with a consistent El Niño-precipitation relationship were determined based on this unique definition of El Niño and season of year. The latter analysis confirms previous studies and suggests other areas of significant signal over the oceans (Gulf of Alaska). The former analysis reveals subtle shifts in tropical rainfall from onset to decay, namely negative anomalies moving from the Maritime Continent and South Pacific to the north tropical Pacific and positive anomalies from the central equatorial Pacific southeastward. These distributions of tropical convection appear to be connected to extratropical precipitation anomalies through meridional atmospheric circulations, concentrated in the eastern Indian Ocean sector during onset and in the Pacific sector during decay. The Yangtze River basin, which is known to flood during El Niño, is affected during the entire evolution.