ATMOSPHERIC AEROSOLS AFFECT THE EARTH'S ENERGY BALANCE BY ABSORBING AND SCATTERING SOLAR RADIATION HEATING AND COOLING THE ATMOSPHERE RESPECTIVELY. BETWEEN 20-90% OF THE GLOBAL AEROSOL BURDEN ARE CARBONACEOUS AEROSOLS WHICH ARE BROADLY DIVIDED INTO TWO TYPES: BLACK CARBON (BC) AND ORGANIC CARBON (OC). APPROXIMATELY 61% OF GLOBAL CARBONACEOUS AEROSOL MASS IS EMITTED FROM BIOMASS BURNING (BB) EVENTS. IN NORTH AMERICA BB CONTRIBUTES TO ~36% OF REGIONAL CARBONACEOUS AEROSOL MASS AND THE WAY THESE AEROSOLS AFFECT THE GLOBAL ENERGY BALANCE IS POORLY UNDERSTOOD. THE AR4 AND AR5 REPORTS BY THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE ASSIGNED A "LOW" TO "MEDIUM-LOW" LEVEL OF SCIENTIFIC UNDERSTANDING FOR BB AEROSOL RADIATIVE PROPERTIES ATTRIBUTED TO POOR SCIENTIFIC UNDERSTANDING OF THE SPATIAL AND TEMPORAL AEROSOL MASS DISTRIBUTION AND AEROSOL OPTICAL PROPERTIES AND THEIR OVER-SIMPLIFIED PARAMETERIZATIONS IN CLIMATE MODELS. THE BODY OF KNOWLEDGE ON AEROSOL RADIATIVE PROPERTIES IS GROWING RAPIDLY. HOWEVER THERE IS A DISCONNECT BETWEEN LABORATORY MEASUREMENTS AND THEIR APPLICABILITY TO THE REAL WORLD. THE FATES OF THESE AEROSOLS AS THEY ARE TRANSPORTED THROUGH THE ATMOSPHERE AND SUBJECTED TO PHOTOCHEMICAL PROCESSES IS UNDERSTUDIED. RECENT ADVANCES IN LABORATORY TECHNOLOGY SUCH AS OXIDATION FLOW TUBE REACTORS (OFR) HAVE ALLOWED EXPERIMENTS OF UP TO TWO WEEKS OF EQUIVALENT ATMOSPHERIC AGING TO BE CONDUCTED AT EXTREMELY SHORT TIME SCALES OFTEN ON THE ORDER OF MINUTES. THESE TECHNIQUES ARE STILL IN THEIR ADOLESCENCE THOUGH THEY ARE GROWING INCREASINGLY POPULAR AS MODELING STUDIES DEMONSTRATE THAT THE ENVIRONMENT INSIDE OFRS DO CLOSELY MIMIC REAL-WORLD CONDITIONS. THE PROPOSED RESEARCH WILL ADDRESS THE FOLLOWING RESEARCH QUESTIONS IN ALIGNMENT WITH NASA'S FIREX-AQ FIELD STUDY GOALS: 1. HOW SENSITIVE ARE BIOMASS BURNING (BB) AEROSOL OPTICAL PROPERTIES TO VARIATIONS IN FUEL TYPE AND FIRE PHASE? 2. HOW DO THE AEROSOL OPTICAL PROPERTIES EVOLVE WITH PLUME AGE AND ATMOSPHERIC PROCESSING? HOW DOES THE ABSORPTION BEHAVIOR OF BROWN CARBON CHANGE WITH ATMOSPHERIC PHOTOOXIDATION? 3. HOW WELL DO RESULTS FROM LABORATORY STUDIES COMPARE WITH THOSE FROM REAL-WORLD FIRES? FIREX-AQ IS A JOINT NOAA/NASA CAMPAIGN PLANNED FOR THE SUMMER OF 2019. THIS COLLABORATIVE MISSION IS A COMPREHENSIVE STUDY OF WILDFIRES ACROSS THE WESTERN UNITED STATES AND WILL COMBINE MULTIPLE AIRCRAFT OBSERVATIONS WITH SURFACE MEASUREMENTS AND SATELLITE REMOTE SENSING DATA TO STUDY AMBIENT AEROSOL DURING LONG-RANGE TRANSPORT AND PROCESSING. CONSTRAINING THE FUNDAMENTAL AEROSOL OPTICAL PROPERTIES IS KEY TOWARD REDUCING THE UNCERTAINTIES IN RADIATIVE FORCING BY WILDFIRE AEROSOL EMISSIONS AND WILL ENABLE RESEARCH GROUPS TO BETTER DESIGN LABORATORY EXPERIMENTS THAT ARE MORE APPLICABLE TO REAL-WORLD PHENOMENA. THE PROPOSED STUDY PLAN WILL OCCUR IN TWO PHASES: INSTRUMENT PREPARATION AND THE FIELD CAMPAIGN. IN THE FIRST PHASE A MULTIWAVELENGTH INTEGRATED PHOTOACOUSTIC-NEPHELOMETER (IPN) SPECTROMETER WILL BE CONSTRUCTED CALIBRATED AND TESTED. THIS INSTRUMENT WILL BE CAPABLE OF MEASURING THE AEROSOL LIGHT ABSORPTION AND SCATTERING COEFFICIENTS AT THREE WAVELENGTHS (405 561 AND 637 NM). THE SECOND PHASE WILL BE THE FIREX-AQ FIELD CAMPAIGN AND SUBSEQUENT DATA ANALYSIS INTERPRETATION AND COMMUNICATION. PER THE FIREX-AQ ANNOUNCEMENT MEMORANDUM BOTH GROUND- AND AIRCRAFT-BASED MEASUREMENTS WILL BE POSSIBLE. WHILE THE IPN UNDER CONSTRUCTION WILL RUGGEDIZED FOR AIRCRAFT MEASUREMENTS A GROUND-BASED APPROACH WILL BE MORE FEASIBLE ESPECIALLY WHEN COMBINING AMBIENT MEASUREMENTS WITH MEASUREMENT OF ARTIFICIALLY AGED AEROSOLS. THE ANTICIPATED RESULTS WILL BE USEFUL FOR CLIMATE MODELING AND SATELLITE RETRIEVAL ALGORITHMS AND FOR INFORMING THE DESIGN OF FUTURE LABORATORY EXPERIMENTS THAT MORE CLOSELY REPRESENT REAL ATMOSPHERIC PHENOMENA