MINERAL DUST AEROSOLS PLAY AN IMPORTANT ROLE IN A SERIES OF CHEMICAL AND PHYSICAL PROCESSES IN THE EARTH'S ATMOSPHERIC SYSTEM. THE SPATIAL AND TEMPORAL DUST DISTRIBUTIONS AND THE TOTAL DUST MASS LOADING ARE KEY PARAMETERS FOR QUANTIFYING THE EFFECTS OF DUST RELATED PROCESSES IN REGIONAL AND GLOBAL SCALES. THE MAIN GOALS OF THIS STUDY ARE TO EVALUATE DUST SIMULATIONS DISTRIBUTIONS NEAR DUST SOURCES IN THE NORTH AFRICA AND MIDDLE EAST AND TO ASSESS HOW THEY ARE IMPACTED BY AEROSOL DATA ASSIMILATION IN THE GEOS-5 EARTH SYSTEM MODEL TO IDENTIFY THE CONTRIBUTION OF APPORTIONED DUST SOURCES TO THE TOTAL DUST MASS LOADING AND TO INVESTIGATE THE ABILITY OF THE MODEL TO SIMULATE OBSERVED TRENDS IN DUSTINESS. FIRST WE WILL FOCUS OUR EFFORTS IN THE EVALUATION OF MODEL SIMULATIONS ALREADY PERFORMED INCLUDING THE ORIGINAL MERRAERO AEROSOL REANALYSIS THE MORE RECENT MERRA-2 JOINT ATMOSPHERIC AND AEROSOL REANALYSIS AND THE MERRA-2 REPLAY REANALYSIS PERFORMED WITHOUT AEROSOL DATA ASSIMILATION. IN ADDITION TO INVESTIGATING DUST EMISSION AND TRANSPORT FEATURES IN THE RESPECTIVE SIMULATIONS WE WILL EXPLORE THE ROLE OF AEROSOL DATA ASSIMILATION IN IMPROVING THE ACCURACY OF THE DUST REPRESENTATION IN THE MODEL WITH RESPECT TO INDEPENDENT OBSERVATIONS FROM SATELLITE GROUND-BASED AND IN SITU AIRCRAFT MEASUREMENTS. FOR THAT PURPOSE WE WILL PERFORM DETAILED TARGET EXPERIMENTS WHERE THE MODEL IS SAMPLED COINCIDENTLY WITH RELEVANT LOCATIONS AND PERIODS WHERE INDEPENDENT DATA SETS EXIST. IN THE SECOND PART WE WILL IMPLEMENT AN APPORTIONMENT STUDY OF DUST SOURCES IN GEOS-5 TO ASSESS THE CONTRIBUTION AND OVERALL IMPORTANCE OF DUST SOURCES FOR THE DUST MASS LOADING. FINALLY WE WILL EVALUATE THE ABILITY OF THE MODEL TO REPRESENT OBSERVED TRENDS IN DUSTINESS. THE INTEGRATION OF MODELS AND MEASUREMENTS PROPOSED IN THIS STUDY WILL IMPROVE OUR UNDERSTANDING OF DUST PROCESSES AND THE IMPORTANCE OF DIFFERENT DUST SOURCES TO THE OVERALL DUST GLOBAL BUDGET. IN ADDITION THIS STUDY HAS A BROAD IMPLICATION FOR AIR QUALITY AND FOR OBSERVING SIMULATION FOR FORECAST AND FUTURE FIELD CAMPAIGNS INCLUDING TRANSPORT AND DEPOSITION THAT ARE IMPORTANT TO OCEAN AND LAND FERTILIZATION. LIKEWISE THIS STUDY WILL CONTRIBUTE TO THE UNDERSTANDING OF THE DUST LIFECYCLE IN THE ATMOSPHERE AND ULTIMATELY TO THE ASSESSMENT OF THE IMPORTANCE OF DUST PROCESSES. THESE EFFORTS ADDRESS NASA STRATEGIC NEEDS TO BETTER UNDERSTAND THE DYNAMICS OF ATMOSPHERIC COMPOSITION AND HOW IT HAS CHANGED OVER TIME.