CLOUDS HAVE A MAJOR INFLUENCE ON THE ENERGY BUDGET OF THE RAPIDLY CHANGING ARCTIC BUT MODELS DO NOT REPRODUCE ARCTIC CLOUD PROPERTIES WELL IN PART BECAUSE OF POORLY UNDERSTOOD PROCESSES SUCH AS AEROSOL-MEDIATED FREEZING. MARINE AEROSOLS IN PARTICULAR HAVE AN IMPORTANT IMPACT ON ARCTIC CLOUD PROPERTIES BEING A LARGE REGIONAL SOURCE OF CLOUD CONDENSATION NUCLEI (CCN) AND ICE NUCLEATING PARTICLES (INPS). HOWEVER MANY KEY FACTORS IN MARINE AEROSOLS AND THEIR INTERACTIONS WITH CLOUDS ARE NOT WELL UNDERSTOOD. OUR TEAM AIMS TO ADDRESS TWO CENTRAL QUESTIONS: 1) WHAT CONTROLS MARINE AEROSOL EMISSIONS OVER THE ARCTIC AND 2) TO WHAT EXTENT DO RADIATIVELY IMPORTANT ARCTIC CLOUD PROPERTIES CORRELATE WITH PROXIES FOR MARINE BIOLOGICALLY DERIVED AEROSOLS? TO ANSWER THE ABOVE QUESTIONS WE WILL USE MODEL OUTPUT FROM TWO WIDELY USED PRODUCTS: THE FLEXIBLE PARTICLE DISPERSION MODEL (FLEXPART) AND THE MODERN-ERA RETROSPECTIVE ANALYSIS FOR RESEARCH AND APPLICATIONS VERSION 2 (MERRA-2) REANALYSIS. WE WILL ALSO USE CLOUD AND AEROSOL REMOTE SENSING DATA FROM THE MODERATE RESOLUTION IMAGING SPECTRORADIOMETER (MODIS) MULTIANGLE IMAGING SPECTRORADIOMETER (MISR) AND CLOUD-AEROSOL LIDAR AND INFRARED PATHFINDER SATELLITE OBSERVATION (CALIPSO) AND CLOUDSAT DATASETS AND OTHER ANCILLARY REMOTE SENSING AND FIELD DATASETS (E.G. FROM NASA S NORTH ATLANTIC AEROSOLS AND MARINE ECOSYSTEMS STUDY (NAAMES) CAMPAIGN). WE HAVE THREE MAIN OBJECTIVES: 1) BETTER VALIDATING FLEXPART MODEL AND MERRA-2 REANALYSIS AEROSOL TRANSPORT OVER THE ARCTIC USING CALIPSO AND MISR FOCUSING ON DUST AND COMBUSTION AEROSOLS. VALIDATION FOR THESE PRODUCTS FOR THE CURRENT APPLICATION IS INCOMPLETE EVEN THOUGH THEY ARE OFTEN THE ONLY WAY TO IDENTIFY CLEAN FROM POLLUTED AEROSOL CONDITIONS IN THE CLOUDY AND SPARSELY SAMPLED ARCTIC. THEREFORE THIS IS A FIRST CRITICAL FIRST STEP IN UNDERSTANDING AEROSOL-CLOUD INTERACTIONS. 2) UNDERSTANDING THE FACTORS CONTROLLING MARINE AEROSOL OPTICAL DEPTH (AOD) CCN AND INP LEVELS. LEVERAGING MODIS NEW MISR CAPABILITIES AND A SERIES OF RECENT FIELD STUDIES WE WILL IDENTIFY AND QUANTIFY THE FACTORS DRIVING ARCTIC AOD LEVELS AND CCN AND INP EMISSIONS ON COMMONLY OBSERVED MARINE-AEROSOL-DOMINATED DAYS. THIS STUDY WILL BE THE MOST COMPREHENSIVE STUDY OF THIS TYPE TO DATE AND WILL LEAD TO BETTER PREDICTION OF THESE ATMOSPHERIC COMPONENTS IN REMOTE REGIONS REDUCED UNCERTAINTY IN FUTURE CHANGES TO CLOUDS AND THE ARCTIC ENERGY BUDGET AND MORE TARGETED FUTURE FIELD STUDIES. 3) QUANTIFYING HOW PHYTOPLANKTON BLOOMS AND WAVE-GENERATED MARINE AEROSOL IMPACT CLOUD PROPERTIES. WE WILL COMPARE LOW LIQUID CONTAINING ARCTIC CLOUD PROPERTIES IN BLOOM AND NON-BLOOM REGIONS USING A LARGE REMOTE SENSING DATASET FLEXPART AND MERRA-2 AEROSOL OUTPUT AND OUR TEAM S PREVIOUSLY DEVELOPED METHOD FOR REDUCING UNCERTAINTY FROM CONFOUNDING METEOROLOGICAL CO-VARIABILITY SIGNALS. THIS APPROACH WILL PROVIDE THE MOST RELIABLE REGIONAL ESTIMATE OF THESE IMPACTS TO DATE. THIS WORK WILL BETTER CONSTRAIN THE FACTORS AFFECTING THE EMISSIONS AND CLOUD IMPACTS OF MARINE ARCTIC AEROSOLS ULTIMATELY ENABLING A BETTER UNDERSTANDING OF HOW ENVIRONMENTAL CHANGES WILL IMPACT THE FUTURE ARCTIC. THE EFFORT IS RESPONSIVE TO THE NASA ROSES NRA (A.19) ATMOSPHERIC COMPOSITION: MODELING AND ANALYSIS PROGRAM S INTEREST IN CHEMISTRY/CLIMATE INTERACTIONS. SPECIFICALLY IT WOULD LEVERAGE AN INTEGRATED OBSERVATION STRATEGY TO ENABLE BETTER UNDERSTANDING THE FACTORS THAT CONTRIBUTE TO CLOUD CONDENSATION NUCLEI AND ICE NUCLEATING PARTICLE FORMATION IN THE ATMOSPHERE AND SUBSEQUENT IMPACTS ON CLOUDS AND THEIR RADIATIVE EFFECTS. THE FINDINGS WILL PROVIDE NEW INSIGHTS ON WHAT CONTROLS THE INTERANNUAL ARCTIC OCEAN CLOUD VARIABILITY AND HOW CHANGES TO EMISSIONS AND ECOSYSTEMS WILL IMPACT FUTURE ARCTIC OCEAN CLOUDS.