THE OBJECTIVE OF THE PROPOSED 5-YEAR PROJECT IS TO DEPLOY THE DIFFERENTIAL AEROSOL SIZING AND HYGROSCOPICITY SPECTROMETER PROBE (DASH-SP) ON THE NASA P-3B DURING THE CLOUD AND AEROSOL MONSOONAL PROCESSES-PHILIPPINES EXPERIMENT (CAMP2EX) FOLLOWED BY PROCESSING DISSEMINATION AND ANALYSIS OF COLLECTED DATA. THE DASH-SP WAS DEVELOPED SPECIFICALLY FOR AIRCRAFT EXPERIMENTS TO PROVIDE RAPID MEASUREMENTS OF SIZE-RESOLVED AEROSOL HYGROSCOPIC GROWTH FACTOR (GF = RATIO OF HUMIDIFIED DIAMETER TO DRY DIAMETER) AND THE REAL COMPONENT OF THE DRY PARTICLE REFRACTIVE INDEX (RI). RAPID AND SIZE-RESOLVED MEASUREMENTS OF THIS NATURE HAVE YET TO BE COLLECTED ON AN AIRBORNE PLATFORM IN THE STUDY REGION WHICH CAN HELP ADVANCE KNOWLEDGE OF AEROSOL-WATER INTERACTIONS AND AEROSOL RADIATIVE FORCING. HIGH TIME RESOLUTION DATA (AS FAST AS ~1 HZ) FROM THE DASH-SP CAN BE MEANINGFULLY COMPARED WITH OTHER SIMULTANEOUS RAPID MEASUREMENTS INCLUDING THOSE FOR GAS- AND AEROSOL-PHASE COMPOSITION AS WELL AS CLOUD CONDENSATION NUCLEI (CCN) CONCENTRATIONS ALL OF WHICH CAN BE USED TO CONDUCT CLOSURE STUDIES TO VALIDATE AND IMPROVE MODEL PARAMETERIZATIONS OF WATER UPTAKE. ADDITIONALLY THE PROPOSED MEASUREMENTS OF AEROSOL HYGROSCOPICITY AND REFRACTIVE INDEX WILL BE HELPFUL FOR USING AND INTERPRETING REMOTE SENSING DATA. SPECIFIC PROJECT TASKS WILL INCLUDE THE FOLLOWING IN ORDER OF OCCURRENCE: (I) PREPARATION AND INTEGRATION OF THE DASH-SP ON THE P-3B; (II) OPERATION OF THE DASH-SP DURING TEST AND RESEARCH FLIGHTS; (III) SUBMISSION OF PRELIMINARY DATA AFTER EACH FLIGHT; (IV) DE-INTEGRATION OF DASH-SP AFTER THE CAMPAIGN; (V) SUBMISSION OF FINAL DATA; AND (VI) DATA ANALYSIS AND COLLABORATION FOCUSED ON PEER-REVIEWED PUBLICATION(S) AS WELL AS PRESENTATIONS AT MAJOR SCIENTIFIC CONFERENCES AND SCIENCE TEAM MEETINGS. THE DASH-SP HAS BEEN SUCCESSFULLY DEPLOYED IN FOUR AIRCRAFT FIELD STUDIES INCLUDING ON THE NASA DC-8 DURING DC3 AND SEAC4RS. THE PROPOSED RESEARCH IS DIRECTLY RELEVANT TO NASA STRATEGIC GOALS AS THE DATA COLLECTED WILL HELP ADDRESS HOW NATURAL AND HUMANINDUCED CHANGES ALTER AIR QUALITY AS WELL AS THE PLANET S RADIATION BALANCE AND HYDROLOGIC CYCLE. DASH-SP MEASUREMENTS HAVE DIRECT RELEVANCE TO THE RADIATION SCIENCES PROGRAM WHICH SUPPORTS STUDIES TO IMPROVE THE THEORETICAL UNDERSTANDING OF RADIATIVE TRANSFER AS WELL AS FIELD MEASUREMENTS OF AEROSOL AND CLOUD PARTICLE CONCENTRATION COMPOSITION MICROPHYSICS AND OPTICAL PROPERTIES. THE RESULTS WILL BE USED TO IMPROVE PARAMETERIZATIONS OF AEROSOL-WATER INTERACTIONS IN ATMOSPHERIC MODELS. THE COLLECTED DATA WILL BE HIGHLY COMPLEMENTARY TO OTHER MEASUREMENTS ON THE P-3B DURING CAMP2EX IN ADDITION TO BEING BENEFICIAL FOR INTERPRETING AND USING REMOTE SENSING DATA.