Evolution of the 2015/16 El Niño and historical perspective since 1979

The 2015/16 El Niño developed from weak warm conditions in late 2014 and NINO3.4 reached 3oC in November 2015. We describe the characteristics of the evolution of the 2015/16 El Niño using various data sets including SST, surface winds, outgoing longwave radiation and subsurface temperature from an ensemble operational ocean reanalyses, and place this event in the context of historical ENSO events since 1979. One salient feature about the 2015/16 El Niño was a large number of westerly wind bursts and downwelling oceanic Kelvin waves (DWKVs). Four DWKVs were observed in April-November 2015 that initiated and enhanced the eastern-central Pacific warming. Eastward zonal current anomalies associated with DWKVs advected the warm pool water eastward in spring/summer. An upwelling Kelvin wave (UWKV) emerged in early November 2015 leading to a rapid decline of the event. Another outstanding feature was that NINO4 reached a historical high (1.7oC), which was 1oC (0.8oC) higher than that of the 1982/83 (1997/98) El Niño. Although NINO3 was comparable to that of the 1982/83 and 1997/98 El Niño, NINO1+2 was much weaker. Consistently, enhanced convection was displaced 20 degree westward, and the maximum D20 anomaly was about 1/3−1/2 of that in 1997 and 1982 near the west coast of South America.