1122 Analysis of the 2015-16 El Niño Event using the NASA's GEOS Data Assimilation System

Wednesday, 25 January 2017
Young-Kwon Lim, GSFC, Greenbelt, MD; and R. Kovach, S. Pawson, and G. Vernieres

The strong El Niño event that occurred in 2015-2016 is analyzed using atmospheric and oceanic analysis produced by the Goddard Earth Observing System (GEOS) systems. A theme of the work is to compare and contrast this event with two other strong El Niños, in 1982-1983 and 1997-1998 that are included in the satellite-data of the MERRA and MERRA-2 reanalyses using the GEOS system.
Distribution of the maximum anomalies of tropical sea-surface temperature, precipitation, Walker circulation, and cloud fraction indicates that 2015–2016 is a Central Pacific (CP) El Niño. Warming extending to the west of the dateline and extra-tropical Pacific due to this CP El Niño, the positive phase of the Pacific Decadal Oscillation, and the decadal warming trend over the western Pacific, Maritime Continent, and Indian Ocean favor construction of the wide distribution of warming over most of the Pacific and Indian Ocean. Compared to 1997–98, subsurface water temperature exhibits a weaker zonal gradient along the equatorial Pacific and a shallower thermocline over the Eastern Pacific (EP). Compared to 1997-1998, the 2015-2016 El Niño event has an earlier onset, with extremely strong warming and precipitation over the Central Pacific; in contrast, the 1997–1998 El Niño exhibits more rapid growth over the Tropics due to stronger westerly wind bursts and Madden-Julian Oscillation during spring, driving the strongest EP El Niño.
The major extra-tropical teleconnections associated with the El Niño in 2015–16 are at least comparable to the teleconnections in the other two El Niño events. Specifically, the Pacific North American (PNA) teleconnection is strongest of these three El Niño events, leading to relatively larger extra-tropical anomalies of geopotential height, temperature, and precipitation over North America in 2015–2016.
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