THE SAHARAN AIR LAYER (SAL) HAS FREQUENTLY BEEN DESCRIBED AS AN INHIBITING INFLUENCE ON HURRICANE GENESIS AND INTENSIFICATION IN THE ATLANTIC BASIN. MORE RECENT STUDIES HAVE SUGGESTED THAT ITS INFLUENCE CAN AT TIMES AID STORM INTENSIFICATION OR AT LEAST NOT CONSISTENTLY BE A NEGATIVE INFLUENCE. MANY OF THE STUDIES HAVE REACHED CONCLUSIONS ABOUT THE SAL BASED ON CIRCUMSTANTIAL EVIDENCE WITHOUT BEING ABLE TO PROVIDE A MORE QUANTITATIVE ASSESSMENT OF THE SAL S ROLE. MODELING STUDIES WITH SAHARAN DUST EFFECTS INCLUDED TEND TO RELY ON A FEW DETERMINISTIC MODEL RUNS (I.E. WITH OR WITHOUT DUST PLUS OTHER VARIATIONS). HOWEVER THEY DO NOT CONSIDER THE UNCERTAINTY OF THOSE SIMULATIONS THAT CAN BE RELATED TO SMALL RANDOM PERTURBATIONS WITHIN THE RANGE OF OBSERVATION UNCERTAINTIES. A MAJOR GOAL OF THIS PROPOSAL IS TO EXAMINE THREE HURRICANES THAT HAVE OCCURRED DURING NASA AIRBORNE HURRICANE EXPERIMENTS INCLUDING HURRICANES HELENE (2006 NAMMA) EARL (2010 GRIP) AND NADINE (2012 HS3) THAT ALL INTERACTED WITH THE SAL BUT SPANNED MAXIMUM INTENSITIES FROM MINIMAL HURRICANE (NADINE) TO CATEGORY 3 HURRICANE (HELENE) TO CATEGORY 4 HURRICANE (EARL). WE PLAN TO CONDUCT 30-MEMBER ENSEMBLE MODEL SIMULATIONS WITH AND WITHOUT THE EFFECTS OF AEROSOLS AND APPLY CORRELATION STATISTICAL ANALYSIS TO IDENTIFY THE ROLE OF THE SAL AND OTHER LARGE-SCALE PROCESSES (E.G. TROUGH INTERACTIONS LARGE-SCALE WIND SHEAR) IN INTENSIFICATION OF THESE THREE HURRICANES. WE WILL QUANTIFY THE IMPACT OF THE AEROSOLS BY EXAMINING INTENSITY DIFFERENCES BETWEEN ENSEMBLE MEMBERS WITH AND WITHOUT AEROSOLS. WE WILL DESCRIBE THE OBSERVED EVOLUTION OF THE HURRICANES AND THEIR RELATIONSHIP TO THE SAL THROUGH ANALYSIS OF GRIP/HS3 AIRCRAFT OBSERVATIONS AND SATELLITE REMOTE-SENSING DATA (E.G. MODIS AIRS AMSR-E TRMM CLOUDSAT) DATA AND USE THE HIGH-RESOLUTION ENSEMBLE SIMULATIONS TO HELP ANSWER THE FOLLOWING EARTH SCIENCE RESEARCH QUESTIONS: 1) WHAT IS THE INFLUENCE OF THE LARGE-SCALE ENVIRONMENT PARTICULARLY THE SAL ON HURRICANE INTENSITY CHANGE; 2) WHAT IS THE EFFECT OF DUST-RADIATION-MICROPHYSICS INTERACTION ON STORM INTERNAL PROCESSES; AND 3) WHAT FACTORS CAUSE SOME STORMS TO WEAKEN AND OTHERS TO INTENSIFY IN THE PRESENCE OF THE SAL? THESE QUESTIONS ARE HIGHLY RELEVANT TO THE OBJECTIVES STATED IN SECTION 2.1 OF THE WEATHER AND ATMOSPHERIC DYNAMICS ANNOUNCEMENT. SIMULATIONS WILL USE A NUMERICAL MODEL THAT INCLUDES DUST EMISSION TRANSPORT AND INTERACTION WITH RADIATION AND MICROPHYSICS THAT ARE ESSENTIAL TO ADDRESSING THE ROLE OF SAHARAN DUST. OUR RECENT SOFTWARE EFFORTS WITH THE NASA UNIFIED WEATHER RESEARCH AND FORECASTING (NU-WRF) MODEL HAS COUPLED THE GODDARD MICROPHYSICS AND LONGWAVE/SHORTWAVE SCHEMES WITH THE GODDARD CHEMISTRY AEROSOL RADIATION AND TRANSPORT (GOCART) MODEL AND WRF-CHEM TO ACCOUNT FOR THE AEROSOL DIRECT (RADIATION) AND INDIRECT (CLOUD MICROPHYSICS) EFFECTS. WE PLAN TO CONDUCT HIGH-RESOLUTION (3 KM OR FINER) MODEL SIMULATIONS OF HURRICANES USING THIS IMPROVED NUWRF MODEL WITH EXPLICIT AEROSOL-MICROPHYSICS-RADIATION.