THIS IS A PROPOSAL TO STUDY THE IMPACT OF MERIDIONAL CROSS-EQUATORIAL WINDS ON ENSO DYNAMICS. OUR GOAL IS TO INVESTIGATE WHETHER VARIATIONS IN THESE WINDS ON DIFFERENT TIMESCALES PLAY A SIGNIFICANT ROLE IN THE ENSO CYCLE AFFECTING THE DEVELOPMENT OF EL NINO EVENTS AND THE BEHAVIOR OF INTERTROPICAL CONVERGENCE ZONE (ITCZ). WE WILL FOCUS ON (I) THE EFFECT OF INTRASEASONAL ANOMALIES IN MERIDIONAL WINDS (OR WIND SURGES) AND (II) THE IMPACTS OF DECADAL TRENDS IN BACKGROUND MERIDIONAL WINDS. ON INTRASEASONAL TIMESCALES SHORT-TERM CROSS-EQUATORIAL WIND ANOMALIES COULD SHAPE THE EVOLUTION OF PARTICULAR EL NINO EVENTS WHILE ON DECADAL/ INTERDECADAL TIMESCALES PERSISTENT CROSS-EQUATORIAL WIND ANOMALIES AS PART OF CHANGES IN THE MEAN STATE OF THE TROPICAL PACIFIC CAN MODULATE ENSO CHARACTERISTICS SUCH AS ITS AMPLITUDE FREQUENCY AND ASSOCIATED SST AND PRECIPITATION PATTERNS. IN CONTRAST TO THE EFFECT OF ZONAL WINDS CENTRAL TO ENSO CYCLE THE POTENTIAL ROLE OF MERIDIONAL WINDS HAS BEEN LARGELY OVERLOOKED. THIS WORK IS MOTIVATED BY RECENT STUDIES FOCUSING ON THE WEAK 2014 EL NINO EVENT WHICH WAS AFFECTED BY A STRONG MID-SUMMER SURGE IN CROSS-EQUATORIAL WINDS. ADDITIONALLY OBSERVATIONS SUGGEST A DECADAL STRENGTHENING OF MEAN CROSS-EQUATORIAL WINDS SINCE THE LATE 1990S ACCOMPANIED BY A SHIFT IN THE ENSO CYCLE: EL NINO AMPLITUDE HAS WEAKENED WHILE THE FREQUENCY OF CENTRAL PACIFIC (CP) EVENTS RELATIVE TO EASTERN PACIFIC (EP) EVENTS HAS INCREASED. CONCURRENTLY THE ITCZ STOPPED CROSSING THE EQUATOR DURING EL NINO AS WAS TYPICAL BEFORE THE YEAR 2000. THE IMPORTANCE OF MERIDIONAL WINDS IS FURTHER CORROBORATED BY OUR PRELIMINARY NUMERICAL EXPERIMENTS: AS WE STRENGTHEN CROSS-EQUATORIAL WINDS BY ADDING OPPOSING SURFACE HEAT FLUXES ON BOTH SIDES OF THE EQUATOR IN THE EASTERN PACIFIC EL NINO CHARACTERISTICS AND ITCZ BEHAVIOR CHANGE IN AGREEMENT WITH THESE OBSERVATIONS. THE PROPOSED WORK WILL INCLUDE SEVERAL KEY COMPONENTS. FIRST WE WILL ANALYZE SATELLITE-DERIVED MEASUREMENT OF OCEAN SURFACE WINDS SST SSH AND OTHER VARIABLES TO IDENTIFY CASES WHEN SURGES OF INTRASEASONAL CROSS-EQUATORIAL WINDS MAY HAVE INFLUENCED EL NINO EVOLUTION. WE WILL ASSESS THE OCEAN-ATMOSPHERE CONDITIONS WHEN THESE WIND ANOMALIES OCCURRED AND THE SYSTEM SUBSEQUENT RESPONSE. THEN WE WILL ATTEMPT TO REPLICATE THE EVOLUTION OF THESE SELECTED EL NINO EVENTS IN A CLIMATE MODEL WHICH WILL ALLOW US TO EXPLORE THE DYNAMICS IN MORE DEPTH. SECOND WE WILL REEXAMINE THE SATELLITE OBSERVED TRENDS IN MERIDIONAL WINDS AND COMPARE THEM TO OTHER DATA PRODUCTS. NEXT WE WILL CONDUCT NUMERICAL EXPERIMENTS WHEREIN WE WILL INDUCE PERSISTENT ANOMALIES IN MERIDIONAL WINDS WHICH WILL MATCH THE DECADAL WIND TREND FROM SATELLITE OBSERVATIONS. WE WILL EXAMINE CHANGES IN EL NINO CHARACTERISTICS AND ITCZ BEHAVIOR CAUSED BY THE IMPOSED WIND ANOMALIES AND INVESTIGATE THE PHYSICAL MECHANISMS RESPONSIBLE FOR THESE CHANGES. WE WILL ALSO EXAMINE THE INFLUENCE OF THE DOUBLE-ITCZ PROBLEM ON THE ENSO CYCLE. FINALLY WE WILL ANALYZE PROJECTED FUTURE CHANGES IN CROSSEQUATORIAL WINDS AND THEIR EFFECT ON ENSO IN CMIP5 AND CMIP6 DATA AND WILL COMPARE THESE CHANGES TO THE TRENDS EVIDENT IN SATELLITE OBSERVATIONS OVER THE PAST SEVERAL DECADES. RELEVANCE TO NASA OBJECTIVES: THIS PROJECT WILL USE SATELLITE-BASED OBSERVATIONS IN CONJUNCTION WITH NUMERICAL EXPERIMENTS TO ADVANCE OUR UNDERSTANDING OF ENSO DYNAMICS WHICH WILL HELP TO EXPLAIN THE RECENTLY OBSERVED CHANGES IN ENSO CYCLE AND WILL ALLOW US TO MAKE BETTER FUTURE PROJECTIONS OF ENSO BEHAVIOR. THIS IS DIRECTLY RELEVANT TO NASA EARTH SCIENCE RESEARCH PROGRAM OBJECTIVES TO STUDY HOW THE EARTH SYSTEM IS CHANGING WHAT HAS CAUSED THESE CHANGES AND HOW THE EARTH SYSTEM WILL CHANGE IN THE FUTURE WHICH IS ESPECIALLY IMPORTANT IN VIEW OF ENSO LARGE CLIMATIC AND SOCIO-ECONOMIC IMPACTS STEMMING FROM ITS GLOBAL TELECONNECTIONS. A BETTER UNDERSTANDING OF INTRASEASONAL WIND VARIABILITY WILL ALSO HELP IMPROVE OUR PREDICTION SKILLS FOR EL NINO.