EACH EL NI O EVENT IS UNIQUE AS THE RECENT DEVELOPMENTS IN THE TROPICAL PACIFIC IN 2014 (A WEAK FAILED EVENT) AND IN 2015 (AN EXTREME EVENT) CLEARLY DEMONSTRATE. THESE TWO WARM EVENTS ARE JUST A SMALL PART OF THE OBSERVED BROAD ENSO CONTINUUM WHICH INCLUDES AS END MEMBERS EASTERN PACIFIC (EP) AND CENTRAL PACIFIC (CP) EL NI O EVENTS. SUCH EL NI O DIVERSITY SEEN IN ANOMALIES IN SST WIND STRESS OCEAN CURRENTS AND RELATED CLIMATIC VARIABLES AFFECTING THE TROPICAL PACIFIC COLD TONGUE AND WARM POOL REVEALS DIFFERENT PHYSICAL MECHANISMS INVOLVED IN EL NI O DEVELOPMENT AND COMPLICATES ROBUST PREDICTION OF EL NI O. THIS PROPOSAL AIMS TO INVESTIGATE THE EFFECTS OF INTRASEASONAL WESTERLY AND EASTERLY WIND BURSTS (WWBS AND EWBS) THAT OCCUR IN THE EQUATORIAL PACIFIC ON THE EVOLUTION OF EL NI O EVENTS AND MORE GENERALLY ON EL NI O DIVERSITY INCLUDING THE OCCURRENCE OF EXTREME EVENTS SUCH AS THOSE IN 1997 1982 AND 2015. WHILE WESTERLY BURSTS THAT GENERATE EQUATORIAL DOWNWELLING KELVIN WAVES PRECIPITATING EL NI O HAVE RECEIVED STRONG ATTENTION EASTERLY BURSTS HAVE BEEN ALL BUT IGNORED. THE INTERPLAY BETWEEN WESTERLY AND EASTERLY WIND BURSTS THAT WE ARGUE SHAPES EL NI O DEVELOPMENT WILL BE AT THE FOCUS OF THIS PROPOSAL. ONE OF THE MAJOR QUESTIONS OF THIS PROPOSAL WILL ADDRESS IS WHAT FACTORS CAN LEAD TO AN EXTREME EL NI O EVENT OR PREVENT AN EVENT FROM DEVELOPING INTO AN EXTREME ONE. THE PROJECT WILL INVOLVE A SYNTHESIS OF SATELLITE OBSERVATIONS (WIND VECTORS SSH SST OCEAN CURRENTS SEA SURFACE SALINITY PRECIPITATION OLR) STRESSING THE EFFECTS OF THE WIND BURSTS AND DOCUMENTING DIFFERENT ASPECTS OF EL NI O DIVERSITY. FURTHER THESE OBSERVATIONS WILL INFORM NUMERICAL SIMULATIONS AIMED AT ELUCIDATING THE MECHANISMS CONTRIBUTING TO THE DIFFERENCES BETWEEN EVENTS. PARTICULAR ELEMENTS OF THE PROJECTS INCLUDE INVESTIGATIONS FROM THE PERSPECTIVE OF SATELLITE OBSERVATIONS INTO (I) CHANGES OF EL NI O PROPERTIES DURING THE PAST 40 YEARS AND ITS RELATIONSHIP WITH WIND BURSTS; (II) DETAILS OF THE DEVELOPMENT OF THE PROLONGED EL NI O CONDITIONS IN 2014-2015-2016 THAT CULMINATED IN AN EXTREME WARM EVENT; (III) INTERCOMPARISON OF THE EXTREME EVENTS OF 1982 1997 AND 2015; (IV) INVESTIGATION INTO WEAK EVENTS; (V) CHARACTERISTICS AND IMPACTS OF WWBS AND EWBS AND THEIR STATE-DEPENDENCE; AND (VI) ANALOGUE AND HINDCAST SIMULATIONS WITH A COMPREHENSIVE COUPLED GCM WHEREIN WE SUPERIMPOSE DIFFERENT SEQUENCES OF WESTERLY AND EASTERLY WIND BURSTS TAKEN FROM SATELLITEBASED OBSERVATIONS AND EXAMINE THE INDUCED CHANGES IN THE OCEAN AND THE COUPLED SYSTEM. SOME OF THE KEY QUESTIONS TO ADDRESS: UNDER WHICH CONDITIONS CAN A SUCCESSION OF WESTERLY WIND BURSTS LEAD TO AN EXTREME EVENT? HOW ARE STATE-DEPENDENT WWBS GENERATED? CAN EASTERLY WIND BURSTS SUPPRESS OR DELAY THE DEVELOPMENT OF EVENTS? HOW WOULD A COMBINATION OF WWBS AND EWBS AFFECT THE SYSTEM? DID THE RELATIONSHIP OF WWBS AND EWBS TO THE BASIC OCEAN STATE IN THE PACIFIC CHANGE OVER THE RECENT DECADES? HOW DO WWBS AND EWBS AFFECT THE FLAVOR AND PREDICTABILITY OF A DEVELOPING EVENT? THE PROJECT S ULTIMATE GOAL IS TO UNDERSTAND THE MAIN FACTORS THAT AFFECT EL NI O DEVELOPMENT AND DIVERSITY WITH A PARTICULAR FOCUS ON EXTREME EVENTS. RELEVANCE TO THE LONG-TERM NASA GOALS AND CURRENT SOLICITATION: THE OVERARCHING GOAL OF THIS STUDY IS TO UNDERSTAND THE FUNDAMENTAL PHYSICAL MECHANISMS THAT CONTROL THE DYNAMICS AND PREDICTABILITY OF EL NI O UTILIZING THE MULTIPLICITY OF SATELLITE DATA AVAILABLE AND LOOKING AT THE KEY CHARACTERISTICS OF OCEAN STATE (SUCH AS OCEAN CIRCULATION AND HEAT CONTENT) INVOLVED IN THE IMPACTS OF INTRASEASONAL WIND BURSTS ON THE COUPLED SYSTEM. THIS OBJECTIVE IS DIRECTLY RELEVANT TO THE CURRENT SOLICITATION AND STRATEGIC NASA GOALS BECAUSE OUR ABILITY TO ACCURATELY SIMULATE AND PREDICT EL NI O (ESPECIALLY EXTREME EVENTS) IS CRITICAL FOR CLIMATE PREDICTION ON A VARIETY OF TIMESCALES AND BECAUSE ENSO CHANGES ARE LIKELY TO BE A MAJOR ELEMENT OF THE OCEAN RESPONSE TO CLIMATE CHANGE.