TRANSPORT IN THE TROPICAL LOWER STRATOSPHERE PLAYS A KEY ROLE IN DETERMINING THE DISTRIBUTION OF AND CHANGES IN STRATOSPHERIC OZONE AND OTHER RADIATIVELY-IMPORTANT CONSTITUENTS (E.G. WATER VAPOR AND AEROSOLS). OF PARTICULAR IMPORTANCE IS THE POSSIBILITY THAT STRATOSPHERIC CIRCULATION MAY BE ACCELERATING LEADING TO INCREASED UPWELLING IN THE TROPICAL STRATOSPHERE AND CHANGES IN STRATOSPHERIC COMPOSITION AND STRATOSPHERE-TROPOSPHERE EXCHANGE. PREVIOUS STUDIES OF COMPOSITION AND TRANSPORT HAVE FOCUSED ON TROPICS-WIDE AVERAGE CHARACTERISTICS HOWEVER RECENT OBSERVATIONAL AND MODELING STUDIES OF THE ANNUAL CYCLE OF OZONE AND OTHER TRACERS SHOWS SIGNIFICANT DIFFERENCES BETWEEN THE NORTHERN AND SOUTHERN TROPICS. THESE DIFFERENCES OCCUR BECAUSE THE BALANCE BETWEEN UPWELLING AND HORIZONTAL MIXING DIFFER ON EITHER SIDE OF THE EQUATOR. THIS IMPLIES THE NEED TO REVISE THE PARADIGM OF WELL-MIXED TROPICS AND TO CONSIDER LATITUDINAL VARIATIONS WITHIN THE TROPICS. THE PROPOSED RESEARCH WILL ANALYZE SATELLITE MEASUREMENTS AND SIMULATIONS OF TRACE GASES IN THE TROPICAL LOWER STRATOSPHERE USING THIS NEW VIEW OF THE TROPICAL LOWER STRATOSPHERE. SPECIFICALLY WE WILL: 1) CHARACTERIZE THE DISTRIBUTIONS AND VARIABILITY (INCLUDING THE UNUSUAL EVOLUTION SINCE 2015) OF TRACE GASES IN THE NORTHERN AND SOUTHERN TROPICAL LOWER STRATOSPHERE USING MULTIPLE SATELLITE INSTRUMENTS; 2) EXAMINE INTERANNUAL AND LONG-TERM VARIABILITY CHANGES IN COMPOSITION AND TRANSPORT IN THE TROPICAL LOWER STRATOSPHERE FOR THE PAST AND PROJECTIONS; AND 3) EVALUATE THE REPRESENTATION OF TROPICAL LOWER STRATOSPHERIC TRANSPORT IN CHEMISTRY-CLIMATE MODELS. THIS RESEARCH WILL LEAD TO A BETTER UNDERSTANDING OF THE PROCESSES INVOLVED IN DETERMINING THE TROPICAL LOWER-STRATOSPHERIC CONCENTRATIONS VARIABILITY AND LONG-TERM TRENDS IN OZONE AND OTHER TRACE CONSTITUENTS. THIS UNDERSTANDING WILL ENABLE A MORE ACCURATE INTERPRETATION OF BOTH OZONE RECOVERY AND THE PROJECTED INCREASE IN THE SPEED OF THE STRATOSPHERIC BREWER-DOBSON CIRCULATION. THE PROPOSED RESEARCH IS DIRECTLY RELEVANT TO THE ACMAP RESEARCH ELEMENTS DESCRIBED IN ROSES 2016. WE WILL USE AURA AND OTHER SATELLITE DATA TOGETHER WITH COMPREHENSIVE CHEMISTRY CLIMATE MODELS TO ESTIMATE TRANSPORT PROPERTIES IN THE STRATOSPHERE AND TRACK CHANGES IN STRATOSPHERIC COMPOSITION.