5 AEROSOLS INTERACT WITH THE EARTH SYSTEM BY ABSORBING AND SCATTERING LIGHT, MODIFYING CLOUD PROPERTIES, AND PERTURBING ATMOSPHERIC CIRCULATIONS. WHILE CONSIDERABLE EFFORT HAS BEEN MADE TO QUANTIFY THEIR IMPACT ON THE EARTH S RADIATION BUDGET, FEEDBACK MECHANISMS BETWEEN AEROSOLS AND THE EARTH SYSTEM SERVE AS A SOURCE OF UNCERTAINTY IN ASSESSING CURRENT AND PROJECTING FUTURE CLIMATE (IPCC, 2014). GLOBAL AEROSOL TRANSPORT MODELS PROVIDE HIGH SPATIAL AND TEMPORAL RESOLUTION FOR EXPLORING AEROSOL EARTH SYSTEM INTERACTIONS, THOUGH THE MODEL RESPONSE HAS BEEN SHOWN TO BE SENSITIVE TO THE CHOICE OF AEROSOL OPTICAL PROPERTIES (COLARCO ET AL., 2014). THEREFORE, IT IS CRUCIAL TO ACCURATELY REPRESENT AEROSOL OPTICAL PROPERTIES IN GLOBAL AEROSOL TRANSPORT MODELS. LIDARS PROVIDE DIRECT VERTICAL MEASUREMENTS OF AEROSOL OPTICAL PROPERTIES AND SERVE AS A VALUABLE TOOL FOR IDENTIFYING BIASES IN MODELED AEROSOL OPTICAL PROPERTIES. THE FIRST PART OF THE PROPOSED INVESTIGATION INVOLVES USING NASA AND OTHER LIDAR OBSERVATIONS TO CONSTRAIN AEROSOL OPTICAL PROPERTIES IN A HIGH SPATIAL RESOLUTION, MODEL-BASED AEROSOL REANALYSIS. THE NASA LIDAR DATASET IS EXTENSIVE AND ENCOMPASSES THE EOS PERIOD (2000 PRESENT), PROVIDING MEASUREMENTS OF PARTICULATE BACKSCATTER, EXTINCTION, AND DEPOLARIZATION RATIO AT SEVERAL WAVELENGTHS (355, 532, AND 1064 NM) ON SEVERAL SPACE-BORNE (CALIOP, CATS), AIRBORNE (CPL, HSRL, DIAL), AND GROUND-BASED (MPLNET) PLATFORMS. THE AEROSOL REANALYSIS IS MERRAERO-2DD, BASED ON THE GEOS-5 EARTH SYSTEM MODEL DRIVEN BY METEOROLOGY FROM THE SECOND MERRA-2 ATMOSPHERIC AND AEROSOL REANALYSIS AND ASSIMILATING AEROSOL OPTICAL THICKNESS (AOT) FROM MODIS, MISR, AND AERONET OBSERVATIONS. MERRAERO-2DD IS RUN AT A GLOBAL ~12.5 KM HORIZONTAL RESOLUTION FOR THE EOS PERIOD. MERRAERO-2DD INCLUDES A SIMULATED AEROSOL LIFECYCLE USING THE GOCART SCHEME, AND PROVIDES GLOBAL THREE-DIMENSIONAL FIELDS OF AEROSOL MASS, COMPOSITION, AND OPTICAL PROPERTIES. WHILE MERRAERO-2DD IS CONSTRAINED IN THE TOTAL AEROSOL LOADING THROUGH ASSIMILATION OF AOT, THE AEROSOL VERTICAL DISTRIBUTION AND COMPOSITION ARE SENSITIVE TO ASSUMPTIONS IN THE MODEL PHYSICS AND PRECONFIGURED LOOKUP TABLES OF AEROSOL OPTICAL PROPERTIES. THE OBJECTIVE OF THE FIRST PART OF THE INVESTIGATION IS TO USE LIDAR DATA TO REFINE THE ASSUMPTIONS ABOUT AEROSOL OPTICAL PROPERTIES AND CONTROLS ON THE SIMULATED AEROSOL VERTICAL DISTRIBUTIONS. USING CASE STUDIES IDENTIFIED IN NASA LIDAR DATA, MERRAERO-2DD SIMULATED AEROSOL OPTICAL QUANTITIES WILL BE COMPARED TO THOSE OBSERVED AND CORRECT BIASES WHEN PRESENT. THE SECOND PART OF THE PROPOSED INVESTIGATION IS FOCUSED ON USING THE REFINED MERRAERO-2DD AS THE BASIS FOR AN OBSERVING SYSTEM EXPERIMENT (OSE) IN ORDER TO EXPLORE AEROSOL TYPING CAPABILITIES FOR CURRENT AND FUTURE LIDAR SYSTEMS. FOR TRADITIONAL BACKSCATTER LIDAR APPLICATIONS (E.G. CALIOP), THE PRACTICAL OBJECTIVE OF DETERMINING AEROSOL TYPE HAS BEEN TO CONVERT THE RETRIEVED BACKSCATTER PROFILE TO EXTINCTION FOR COMPARISON WITH MODELS. THIS IS DONE BY ASSIGNING AN EXTINCTION-TO-BACKSCATTER RATIO (I.E., LIDAR RATIO) BASED ON OBSERVED QUANTITIES AND, OFTEN OTHER CONSTRAINTS (E.G., AEROSOL FEATURE ALTITUDE). THESE METHODS CAN LEAD TO SUBSTANTIAL ERRORS IN AEROSOL TYPING WHEN COMPARED TO LIDAR SYSTEMS THAT DIRECTLY MEASURE THE EXTINCTION PROFILE (E.G., HSRL, BURTON ET AL. (2013)). RETRIEVED AEROSOL TYPE HAS ALSO BEEN USED BY THE AEROSOL MODELING COMMUNITY TO IDENTIFY OPTICAL PROPERTY AND TRANSPORT BIASES (NOWOTTNICK ET AL., 2015). CONSTRAINED MERRAERO-2DD RESULTS WILL BE USED TO REFINE CURRENT AEROSOL TYPING CAPABILITIES AND IDENTIFY AN OPTIMIZED SET OF OBSERVED QUANTITIES TO ENHANCE AEROSOL TYPING CAPABILITIES FOR USE BY FUTURE SPACE-BASED LIDAR SYSTEMS (E.G., THE AEROSOL CLOUD ECOSYSTEM MISSION). Funding Only Action ($116) 8/25/20 Not listed AEROSOLS INTERACT WITH THE EARTH SYSTEM BY ABSORBING AND SCATTERING LIGHT MODIFYING CLOUD PROPERTIES AND PERTURBING ATMOSPHERIC CIRCULATIONS. WHILE CONSIDERABLE EFFORT HAS BEEN MADE TO QUANTIFY THEIR IMPACT ON THE EARTH S RADIATION BUDGET FEEDBACK MECHANISMS BETWEEN AEROSOLS AND THE EARTH SYSTEM SERVE AS A SOURCE OF UNCERTAINTY IN ASSESSING CURRENT AND PROJECTING FUTURE CLIMATE (IPCC 2014). GLOBAL AEROSOL TRANSPORT MODELS PROVIDE HIGH SPATIAL AND TEMPORAL RESOLUTION FOR EXPLORING AEROSOL EARTH SYSTEM INTERACTIONS THOUGH THE MODEL RESPONSE HAS BEEN SHOWN TO BE SENSITIVE TO THE CHOICE OF AEROSOL OPTICAL PROPERTIES (COLARCO ET AL. 2014). THEREFORE IT IS CRUCIAL TO ACCURATELY REPRESENT AEROSOL OPTICAL PROPERTIES IN GLOBAL AEROSOL TRANSPORT MODELS. LIDARS PROVIDE DIRECT VERTICAL MEASUREMENTS OF AEROSOL OPTICAL PROPERTIES AND SERVE AS A VALUABLE TOOL FOR IDENTIFYING BIASES IN MODELED AEROSOL OPTICAL PROPERTIES. THE FIRST PART OF THE PROPOSED INVESTIGATION INVOLVES USING NASA AND OTHER LIDAR OBSERVATIONS TO CONSTRAIN AEROSOL OPTICAL PROPERTIES IN A HIGH SPATIAL RESOLUTION MODEL-BASED AEROSOL REANALYSIS. THE NASA LIDAR DATASET IS EXTENSIVE AND ENCOMPASSES THE EOS PERIOD (2000 PRESENT) PROVIDING MEASUREMENTS OF PARTICULATE BACKSCATTER EXTINCTION AND DEPOLARIZATION RATIO AT SEVERAL WAVELENGTHS (355 532 AND 1064 NM) ON SEVERAL SPACE-BORNE (CALIOP CATS) AIRBORNE (CPL HSRL DIAL) AND GROUND-BASED (MPLNET) PLATFORMS. THE AEROSOL REANALYSIS IS MERRAERO-2DD BASED ON THE GEOS-5 EARTH SYSTEM MODEL DRIVEN BY METEOROLOGY FROM THE SECOND MERRA-2 ATMOSPHERIC AND AEROSOL REANALYSIS AND ASSIMILATING AEROSOL OPTICAL THICKNESS (AOT) FROM MODIS MISR AND AERONET OBSERVATIONS. MERRAERO-2DD IS RUN AT A GLOBAL ~12.5 KM HORIZONTAL RESOLUTION FOR THE EOS PERIOD. MERRAERO-2DD INCLUDES A SIMULATED AEROSOL LIFECYCLE USING THE GOCART SCHEME AND PROVIDES GLOBAL THREE-DIMENSIONAL FIELDS OF AEROSOL MASS COMPOSITION AND OPTICAL PROPERTIES. WHILE MERRAERO-2DD IS CONSTRAINED IN THE TOTAL AEROSOL LOADING THROUGH ASSIMILATION OF AOT THE AEROSOL VERTICAL DISTRIBUTION AND COMPOSITION ARE SENSITIVE TO ASSUMPTIONS IN THE MODEL PHYSICS AND PRECONFIGURED LOOKUP TABLES OF AEROSOL OPTICAL PROPERTIES. THE OBJECTIVE OF THE FIRST PART OF THE INVESTIGATION IS TO USE LIDAR DATA TO REFINE THE ASSUMPTIONS ABOUT AEROSOL OPTICAL PROPERTIES AND CONTROLS ON THE SIMULATED AEROSOL VERTICAL DISTRIBUTIONS. USING CASE STUDIES IDENTIFIED IN NASA LIDAR DATA MERRAERO-2DD SIMULATED AEROSOL OPTICAL QUANTITIES WILL BE COMPARED TO THOSE OBSERVED AND CORRECT BIASES WHEN PRESENT. THE SECOND PART OF THE PROPOSED INVESTIGATION IS FOCUSED ON USING THE REFINED MERRAERO-2DD AS THE BASIS FOR AN OBSERVING SYSTEM EXPERIMENT (OSE) IN ORDER TO EXPLORE AEROSOL TYPING CAPABILITIES FOR CURRENT AND FUTURE LIDAR SYSTEMS. FOR TRADITIONAL BACKSCATTER LIDAR APPLICATIONS (E.G. CALIOP) THE PRACTICAL OBJECTIVE OF DETERMINING AEROSOL TYPE HAS BEEN TO CONVERT THE RETRIEVED BACKSCATTER PROFILE TO EXTINCTION FOR COMPARISON WITH MODELS. THIS IS DONE BY ASSIGNING AN EXTINCTION-TO-BACKSCATTER RATIO (I.E. LIDAR RATIO) BASED ON OBSERVED QUANTITIES AND OFTEN OTHER CONSTRAINTS (E.G. AEROSOL FEATURE ALTITUDE). THESE METHODS CAN LEAD TO SUBSTANTIAL ERRORS IN AEROSOL TYPING WHEN COMPARED TO LIDAR SYSTEMS THAT DIRECTLY MEASURE THE EXTINCTION PROFILE (E.G. HSRL BURTON ET AL. (2013)). RETRIEVED AEROSOL TYPE HAS ALSO BEEN USED BY THE AEROSOL MODELING COMMUNITY TO IDENTIFY OPTICAL PROPERTY AND TRANSPORT BIASES (NOWOTTNICK ET AL. 2015). CONSTRAINED MERRAERO-2DD RESULTS WILL BE USED TO REFINE CURRENT AEROSOL TYPING CAPABILITIES AND IDENTIFY AN OPTIMIZED SET OF OBSERVED QUANTITIES TO ENHANCE AEROSOL TYPING CAPABILITIES FOR USE BY FUTURE SPACE-BASED LIDAR SYSTEMS (E.G. THE AEROSOL CLOUD ECOSYSTEM MISSION). ($116) 8/25/20 Not listed AEROSOLS INTERACT WITH THE EARTH SYSTEM BY ABSORBING AND SCATTERING LIGHT MODIFYING CLOUD PROPERTIES AND PERTURBING ATMOSPHERIC CIRCULATIONS. WHILE CONSIDERABLE EFFORT HAS BEEN MADE TO QUANTIFY THEIR IMPACT ON THE EARTH S RADIATION BUDGET FEEDBACK MECHANISMS BETWEEN AEROSOLS AND THE EARTH SYSTEM SERVE AS A SOURCE OF UNCERTAINTY IN ASSESSING CURRENT AND PROJECTING FUTURE CLIMATE (IPCC 2014). GLOBAL AEROSOL TRANSPORT MODELS PROVIDE HIGH SPATIAL AND TEMPORAL RESOLUTION FOR EXPLORING AEROSOL EARTH SYSTEM INTERACTIONS THOUGH THE MODEL RESPONSE HAS BEEN SHOWN TO BE SENSITIVE TO THE CHOICE OF AEROSOL OPTICAL PROPERTIES (COLARCO ET AL. 2014). THEREFORE IT IS CRUCIAL TO ACCURATELY REPRESENT AEROSOL OPTICAL PROPERTIES IN GLOBAL AEROSOL TRANSPORT MODELS. LIDARS PROVIDE DIRECT VERTICAL MEASUREMENTS OF AEROSOL OPTICAL PROPERTIES AND SERVE AS A VALUABLE TOOL FOR IDENTIFYING BIASES IN MODELED AEROSOL OPTICAL PROPERTIES. THE FIRST PART OF THE PROPOSED INVESTIGATION INVOLVES USING NASA AND OTHER LIDAR OBSERVATIONS TO CONSTRAIN AEROSOL OPTICAL PROPERTIES IN A HIGH SPATIAL RESOLUTION MODEL-BASED AEROSOL REANALYSIS. THE NASA LIDAR DATASET IS EXTENSIVE AND ENCOMPASSES THE EOS PERIOD (2000 PRESENT) PROVIDING MEASUREMENTS OF PARTICULATE BACKSCATTER EXTINCTION AND DEPOLARIZATION RATIO AT SEVERAL WAVELENGTHS (355 532 AND 1064 NM) ON SEVERAL SPACE-BORNE (CALIOP CATS) AIRBORNE (CPL HSRL DIAL) AND GROUND-BASED (MPLNET) PLATFORMS. THE AEROSOL REANALYSIS IS MERRAERO-2DD BASED ON THE GEOS-5 EARTH SYSTEM MODEL DRIVEN BY METEOROLOGY FROM THE SECOND MERRA-2 ATMOSPHERIC AND AEROSOL REANALYSIS AND ASSIMILATING AEROSOL OPTICAL THICKNESS (AOT) FROM MODIS MISR AND AERONET OBSERVATIONS. MERRAERO-2DD IS RUN AT A GLOBAL ~12.5 KM HORIZONTAL RESOLUTION FOR THE EOS PERIOD. MERRAERO-2DD INCLUDES A SIMULATED AEROSOL LIFECYCLE USING THE GOCART SCHEME AND PROVIDES GLOBAL THREE-DIMENSIONAL FIELDS OF AEROSOL MASS COMPOSITION AND OPTICAL PROPERTIES. WHILE MERRAERO-2DD IS CONSTRAINED IN THE TOTAL AEROSOL LOADING THROUGH ASSIMILATION OF AOT THE AEROSOL VERTICAL DISTRIBUTION AND COMPOSITION ARE SENSITIVE TO ASSUMPTIONS IN THE MODEL PHYSICS AND PRECONFIGURED LOOKUP TABLES OF AEROSOL OPTICAL PROPERTIES. THE OBJECTIVE OF THE FIRST PART OF THE INVESTIGATION IS TO USE LIDAR DATA TO REFINE THE ASSUMPTIONS ABOUT AEROSOL OPTICAL PROPERTIES AND CONTROLS ON THE SIMULATED AEROSOL VERTICAL DISTRIBUTIONS. USING CASE STUDIES IDENTIFIED IN NASA LIDAR DATA MERRAERO-2DD SIMULATED AEROSOL OPTICAL QUANTITIES WILL BE COMPARED TO THOSE OBSERVED AND CORRECT BIASES WHEN PRESENT. THE SECOND PART OF THE PROPOSED INVESTIGATION IS FOCUSED ON USING THE REFINED MERRAERO-2DD AS THE BASIS FOR AN OBSERVING SYSTEM EXPERIMENT (OSE) IN ORDER TO EXPLORE AEROSOL TYPING CAPABILITIES FOR CURRENT AND FUTURE LIDAR SYSTEMS. FOR TRADITIONAL BACKSCATTER LIDAR APPLICATIONS (E.G. CALIOP) THE PRACTICAL OBJECTIVE OF DETERMINING AEROSOL TYPE HAS BEEN TO CONVERT THE RETRIEVED BACKSCATTER PROFILE TO EXTINCTION FOR COMPARISON WITH MODELS. THIS IS DONE BY ASSIGNING AN EXTINCTION-TO-BACKSCATTER RATIO (I.E. LIDAR RATIO) BASED ON OBSERVED QUANTITIES AND OFTEN OTHER CONSTRAINTS (E.G. AEROSOL FEATURE ALTITUDE). THESE METHODS CAN LEAD TO SUBSTANTIAL ERRORS IN AEROSOL TYPING WHEN COMPARED TO LIDAR SYSTEMS THAT DIRECTLY MEASURE THE EXTINCTION PROFILE (E.G. HSRL BURTON ET AL. (2013)). RETRIEVED AEROSOL TYPE HAS ALSO BEEN USED BY THE AEROSOL MODELING COMMUNITY TO IDENTIFY OPTICAL PROPERTY AND TRANSPORT BIASES (NOWOTTNICK ET AL. 2015). CONSTRAINED MERRAERO-2DD RESULTS WILL BE USED TO REFINE CURRENT AEROSOL TYPING CAPABILITIES AND IDENTIFY AN OPTIMIZED SET OF OBSERVED QUANTITIES TO ENHANCE AEROSOL TYPING CAPABILITIES FOR USE BY FUTURE SPACE-BASED LIDAR SYSTEMS (E.G. THE AEROSOL CLOUD ECOSYSTEM MISSION). $0 4/19/19 4 AEROSOLS INTERACT WITH THE EARTH SYSTEM BY ABSORBING AND SCATTERING LIGHT, MODIFYING CLOUD PROPERTIES, AND PERTURBING ATMOSPHERIC CIRCULATIONS. WHILE CONSIDERABLE EFFORT HAS BEEN MADE TO QUANTIFY THEIR IMPACT ON THE EARTH S RADIATION BUDGET, FEEDBACK MECHANISMS BETWEEN AEROSOLS AND THE EARTH SYSTEM SERVE AS A SOURCE OF UNCERTAINTY IN ASSESSING CURRENT AND PROJECTING FUTURE CLIMATE (IPCC, 2014). GLOBAL AEROSOL TRANSPORT MODELS PROVIDE HIGH SPATIAL AND TEMPORAL RESOLUTION FOR EXPLORING AEROSOL EARTH SYSTEM INTERACTIONS, THOUGH THE MODEL RESPONSE HAS BEEN SHOWN TO BE SENSITIVE TO THE CHOICE OF AEROSOL OPTICAL PROPERTIES (COLARCO ET AL., 2014). THEREFORE, IT IS CRUCIAL TO ACCURATELY REPRESENT AEROSOL OPTICAL PROPERTIES IN GLOBAL AEROSOL TRANSPORT MODELS. LIDARS PROVIDE DIRECT VERTICAL MEASUREMENTS OF AEROSOL OPTICAL PROPERTIES AND SERVE AS A VALUABLE TOOL FOR IDENTIFYING BIASES IN MODELED AEROSOL OPTICAL PROPERTIES. THE FIRST PART OF THE PROPOSED INVESTIGATION INVOLVES USING NASA AND OTHER LIDAR OBSERVATIONS TO CONSTRAIN AEROSOL OPTICAL PROPERTIES IN A HIGH SPATIAL RESOLUTION, MODEL-BASED AEROSOL REANALYSIS. THE NASA LIDAR DATASET IS EXTENSIVE AND ENCOMPASSES THE EOS PERIOD (2000 PRESENT), PROVIDING MEASUREMENTS OF PARTICULATE BACKSCATTER, EXTINCTION, AND DEPOLARIZATION RATIO AT SEVERAL WAVELENGTHS (355, 532, AND 1064 NM) ON SEVERAL SPACE-BORNE (CALIOP, CATS), AIRBORNE (CPL, HSRL, DIAL), AND GROUND-BASED (MPLNET) PLATFORMS. THE AEROSOL REANALYSIS IS MERRAERO-2DD, BASED ON THE GEOS-5 EARTH SYSTEM MODEL DRIVEN BY METEOROLOGY FROM THE SECOND MERRA-2 ATMOSPHERIC AND AEROSOL REANALYSIS AND ASSIMILATING AEROSOL OPTICAL THICKNESS (AOT) FROM MODIS, MISR, AND AERONET OBSERVATIONS. MERRAERO-2DD IS RUN AT A GLOBAL ~12.5 KM HORIZONTAL RESOLUTION FOR THE EOS PERIOD. MERRAERO-2DD INCLUDES A SIMULATED AEROSOL LIFECYCLE USING THE GOCART SCHEME, AND PROVIDES GLOBAL THREE-DIMENSIONAL FIELDS OF AEROSOL MASS, COMPOSITION, AND OPTICAL PROPERTIES. WHILE MERRAERO-2DD IS CONSTRAINED IN THE TOTAL AEROSOL LOADING THROUGH ASSIMILATION OF AOT, THE AEROSOL VERTICAL DISTRIBUTION AND COMPOSITION ARE SENSITIVE TO ASSUMPTIONS IN THE MODEL PHYSICS AND PRECONFIGURED LOOKUP TABLES OF AEROSOL OPTICAL PROPERTIES. THE OBJECTIVE OF THE FIRST PART OF THE INVESTIGATION IS TO USE LIDAR DATA TO REFINE THE ASSUMPTIONS ABOUT AEROSOL OPTICAL PROPERTIES AND CONTROLS ON THE SIMULATED AEROSOL VERTICAL DISTRIBUTIONS. USING CASE STUDIES IDENTIFIED IN NASA LIDAR DATA, MERRAERO-2DD SIMULATED AEROSOL OPTICAL QUANTITIES WILL BE COMPARED TO THOSE OBSERVED AND CORRECT BIASES WHEN PRESENT. THE SECOND PART OF THE PROPOSED INVESTIGATION IS FOCUSED ON USING THE REFINED MERRAERO-2DD AS THE BASIS FOR AN OBSERVING SYSTEM EXPERIMENT (OSE) IN ORDER TO EXPLORE AEROSOL TYPING CAPABILITIES FOR CURRENT AND FUTURE LIDAR SYSTEMS. FOR TRADITIONAL BACKSCATTER LIDAR APPLICATIONS (E.G. CALIOP), THE PRACTICAL OBJECTIVE OF DETERMINING AEROSOL TYPE HAS BEEN TO CONVERT THE RETRIEVED BACKSCATTER PROFILE TO EXTINCTION FOR COMPARISON WITH MODELS. THIS IS DONE BY ASSIGNING AN EXTINCTION-TO-BACKSCATTER RATIO (I.E., LIDAR RATIO) BASED ON OBSERVED QUANTITIES AND, OFTEN OTHER CONSTRAINTS (E.G., AEROSOL FEATURE ALTITUDE). THESE METHODS CAN LEAD TO SUBSTANTIAL ERRORS IN AEROSOL TYPING WHEN COMPARED TO LIDAR SYSTEMS THAT DIRECTLY MEASURE THE EXTINCTION PROFILE (E.G., HSRL, BURTON ET AL. (2013)). RETRIEVED AEROSOL TYPE HAS ALSO BEEN USED BY THE AEROSOL MODELING COMMUNITY TO IDENTIFY OPTICAL PROPERTY AND TRANSPORT BIASES (NOWOTTNICK ET AL., 2015). CONSTRAINED MERRAERO-2DD RESULTS WILL BE USED TO REFINE CURRENT AEROSOL TYPING CAPABILITIES AND IDENTIFY AN OPTIMIZED SET OF OBSERVED QUANTITIES TO ENHANCE AEROSOL TYPING CAPABILITIES FOR USE BY FUTURE SPACE-BASED LIDAR SYSTEMS (E.G., THE AEROSOL CLOUD ECOSYSTEM MISSION). Other Administrative Action $0 4/19/19 Not listed AEROSOLS INTERACT WITH THE EARTH SYSTEM BY ABSORBING AND SCATTERING LIGHT MODIFYING CLOUD PROPERTIES AND PERTURBING ATMOSPHERIC CIRCULATIONS. WHILE CONSIDERABLE EFFORT HAS BEEN MADE TO QUANTIFY THEIR IMPACT ON THE EARTH S RADIATION BUDGET FEEDBACK MECHANISMS BETWEEN AEROSOLS AND THE EARTH SYSTEM SERVE AS A SOURCE OF UNCERTAINTY IN ASSESSING CURRENT AND PROJECTING FUTURE CLIMATE (IPCC 2014). GLOBAL AEROSOL TRANSPORT MODELS PROVIDE HIGH SPATIAL AND TEMPORAL RESOLUTION FOR EXPLORING AEROSOL EARTH SYSTEM INTERACTIONS THOUGH THE MODEL RESPONSE HAS BEEN SHOWN TO BE SENSITIVE TO THE CHOICE OF AEROSOL OPTICAL PROPERTIES (COLARCO ET AL. 2014). THEREFORE IT IS CRUCIAL TO ACCURATELY REPRESENT AEROSOL OPTICAL PROPERTIES IN GLOBAL AEROSOL TRANSPORT MODELS. LIDARS PROVIDE DIRECT VERTICAL MEASUREMENTS OF AEROSOL OPTICAL PROPERTIES AND SERVE AS A VALUABLE TOOL FOR IDENTIFYING BIASES IN MODELED AEROSOL OPTICAL PROPERTIES. THE FIRST PART OF THE PROPOSED INVESTIGATION INVOLVES USING NASA AND OTHER LIDAR OBSERVATIONS TO CONSTRAIN AEROSOL OPTICAL PROPERTIES IN A HIGH SPATIAL RESOLUTION MODEL-BASED AEROSOL REANALYSIS. THE NASA LIDAR DATASET IS EXTENSIVE AND ENCOMPASSES THE EOS PERIOD (2000 PRESENT) PROVIDING MEASUREMENTS OF PARTICULATE BACKSCATTER EXTINCTION AND DEPOLARIZATION RATIO AT SEVERAL WAVELENGTHS (355 532 AND 1064 NM) ON SEVERAL SPACE-BORNE (CALIOP CATS) AIRBORNE (CPL HSRL DIAL) AND GROUND-BASED (MPLNET) PLATFORMS. THE AEROSOL REANALYSIS IS MERRAERO-2DD BASED ON THE GEOS-5 EARTH SYSTEM MODEL DRIVEN BY METEOROLOGY FROM THE SECOND MERRA-2 ATMOSPHERIC AND AEROSOL REANALYSIS AND ASSIMILATING AEROSOL OPTICAL THICKNESS (AOT) FROM MODIS MISR AND AERONET OBSERVATIONS. MERRAERO-2DD IS RUN AT A GLOBAL ~12.5 KM HORIZONTAL RESOLUTION FOR THE EOS PERIOD. MERRAERO-2DD INCLUDES A SIMULATED AEROSOL LIFECYCLE USING THE GOCART SCHEME AND PROVIDES GLOBAL THREE-DIMENSIONAL FIELDS OF AEROSOL MASS COMPOSITION AND OPTICAL PROPERTIES. WHILE MERRAERO-2DD IS CONSTRAINED IN THE TOTAL AEROSOL LOADING THROUGH ASSIMILATION OF AOT THE AEROSOL VERTICAL DISTRIBUTION AND COMPOSITION ARE SENSITIVE TO ASSUMPTIONS IN THE MODEL PHYSICS AND PRECONFIGURED LOOKUP TABLES OF AEROSOL OPTICAL PROPERTIES. THE OBJECTIVE OF THE FIRST PART OF THE INVESTIGATION IS TO USE LIDAR DATA TO REFINE THE ASSUMPTIONS ABOUT AEROSOL OPTICAL PROPERTIES AND CONTROLS ON THE SIMULATED AEROSOL VERTICAL DISTRIBUTIONS. USING CASE STUDIES IDENTIFIED IN NASA LIDAR DATA MERRAERO-2DD SIMULATED AEROSOL OPTICAL QUANTITIES WILL BE COMPARED TO THOSE OBSERVED AND CORRECT BIASES WHEN PRESENT. THE SECOND PART OF THE PROPOSED INVESTIGATION IS FOCUSED ON USING THE REFINED MERRAERO-2DD AS THE BASIS FOR AN OBSERVING SYSTEM EXPERIMENT (OSE) IN ORDER TO EXPLORE AEROSOL TYPING CAPABILITIES FOR CURRENT AND FUTURE LIDAR SYSTEMS. FOR TRADITIONAL BACKSCATTER LIDAR APPLICATIONS (E.G. CALIOP) THE PRACTICAL OBJECTIVE OF DETERMINING AEROSOL TYPE HAS BEEN TO CONVERT THE RETRIEVED BACKSCATTER PROFILE TO EXTINCTION FOR COMPARISON WITH MODELS. THIS IS DONE BY ASSIGNING AN EXTINCTION-TO-BACKSCATTER RATIO (I.E. LIDAR RATIO) BASED ON OBSERVED QUANTITIES AND OFTEN OTHER CONSTRAINTS (E.G. AEROSOL FEATURE ALTITUDE). THESE METHODS CAN LEAD TO SUBSTANTIAL ERRORS IN AEROSOL TYPING WHEN COMPARED TO LIDAR SYSTEMS THAT DIRECTLY MEASURE THE EXTINCTION PROFILE (E.G. HSRL BURTON ET AL. (2013)). RETRIEVED AEROSOL TYPE HAS ALSO BEEN USED BY THE AEROSOL MODELING COMMUNITY TO IDENTIFY OPTICAL PROPERTY AND TRANSPORT BIASES (NOWOTTNICK ET AL. 2015). CONSTRAINED MERRAERO-2DD RESULTS WILL BE USED TO REFINE CURRENT AEROSOL TYPING CAPABILITIES AND IDENTIFY AN OPTIMIZED SET OF OBSERVED QUANTITIES TO ENHANCE AEROSOL TYPING CAPABILITIES FOR USE BY FUTURE SPACE-BASED LIDAR SYSTEMS (E.G. THE AEROSOL CLOUD ECOSYSTEM MISSION). $39.6k 3/13/18