Influence of natural and anthropogenic aerosols on cloud base droplet size distributions in clouds over the South China Sea and West Pacific
Year: 2023
Type: article
Abstract: Cumulus clouds are common over maritime regions. They are important regulators of the global radiative energy budget and global hydrologic cycle, as well as a key contributor to the uncertainty in anthropogenic climate change projections due to uncertainty in aerosol–cloud interactions. These interactions are regionally specific owing to their strong influences on aerosol sources and meteorology. Here, our analysis focuses on the statistical properties of marine boundary layer (MBL) aerosol chemistry and the relationships of MBL aerosol to cumulus cloud properties just above cloud base as sampled in 2019 during the NASA Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP 2 Ex). The aerosol and clouds were sampled by instruments on the NASA P-3 aircraft over three distinct maritime regions around the Philippines: the West Pacific, the South China Sea, and the Sulu Sea. Our analysis shows three primary sources influenced the aerosol chemical composition: clean marine (ocean source), industrial (Southeast Asia, Manila, and cargo and tanker ship emissions), and biomass burning (Borneo and Indonesia). The clean marine aerosol chemical composition had low values of all sampled chemical signatures, specifically median values of 2.2 µg m −3 of organics (ORG), 2.3 µg m −3 of SO 4 , 0.3 µg m −3 of NO 3 , 1.4 µg m −3 of NH 4 , 0.04 µg m −3 of Cl, and 0.0074 µg m −3 of refractory black carbon (BC). Chemical signatures of the other two aerosol source regions were industrial, with elevated SO 4 having a median value of 6.1 µg m −3 , and biomass burning, with elevated median concentrations of ORG 21.2 µg m −3 and BC 0.1351 µg m −3 . Based on chemical signatures, the industrial component was primarily from ship emissions, which were sampled within 60 km of ships and within projected ship plumes. Normalized cloud droplet size distributions in clouds sampled near the MBL passes of the P-3 showed that clouds impacted by industrial and biomass burning contained higher concentrations of cloud droplets, by as much as 1.5 orders of magnitude for diameters < 13 µm compared to clean marine clouds, while at size ranges between 13.0–34.5 µm the median concentrations of cloud droplets in all aerosol categories were nearly an order of magnitude less than the clean marine category. In the droplet size bins centered at diameters > 34.5 µm concentrations were equal to, or slightly exceeded, the concentrations of the clean marine clouds. These analyses show that anthropogenic aerosols generated from industrial and biomass burning sources significantly influenced cloud base microphysical structure in the Philippine region enhancing the small droplet concentration and reducing the concentration of mid-sized droplets.
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDG: Climate action
Open Access status: gold
Estimated APC paid: $1,725
Awards: G1262772034, G219175515, G315056983, THE CLOUDS AEROSOL AND MONSOON PROCESSES-PHILIPPINES EXPERIMENT (CAMP2EX) AIMS TO PROVIDE A DETAILED VIEW OF THE MICROPHYSICS OF AEROSOLS AND CLOUDS IN ADDITION TO ATMOSPHERIC STATE IN THE VICINITY OF THE PHILIPPINES DURING THE SOUTHWEST MONSOON. THE AIRBORNE OBSERVATIONS WILL ALLOW ENHANCING OUR UNDERSTANDING OF THE COMPLEX INTERACTIONS BETWEEN AEROSOLS CLOUDS AND ATMOSPHERIC CONDITIONS. HERE WE PROPOSE TO INCLUDE THE RESEARCH SCANNING POLARIMETER (RSP) INTO THE CAMPAIGN S INSTRUMENT SUITE SINCE THE RSP S UNIQUE COMBINATION OF MULTI-DIRECTIONAL TOTAL AND POLARIZED REFLECTANCES AT VISIBLE AND SHORTWAVE INFRARED WAVELENGTHS AND WITH DENSE ANGULAR SAMPLING PROVIDES CAPABILITIES TO ADDRESS MANY OF THE CAMP2EX OBSERVATIONAL OBJECTIVES. CLOUD PRODUCTS THAT THE RSP DELIVERS OPERATIONALLY INCLUDE CLOUD TOP HEIGHT CLOUD TOP PHASE CLOUD OPTICAL THICKNESS LIQUID DROP SIZE DISTRIBUTION AND THE EFFECTIVE RADIUS SHAPE ROUGHNESS AND ASYMMETRY PARAMETER OF ICE CRYSTALS. RSP RETRIEVALS FOR AEROSOLS PROVIDE AEROSOL OPTICAL DEPTH LAYER HEIGHT EFFECTIVE RADIUS AND VARIANCE OF THE SIZE DISTRIBUTION THE COMPLEX REFRACTIVE INDEX AND THE FRACTION OF NON-SPHERICAL PARTICLES. ALL AEROSOL MICROPHYSICAL PARAMETERS ARE OBTAINED FOR TWO MODES. POLARIMETRIC CLOUD DROPLET SIZE RETRIEVALS ARE HIGHLY ROBUST IN THE SPATIAL INHOMOGENEOUS CLOUD CONDITIONS LIKELY ENCOUNTERED DURING CAMP2EX. RELATIVELY ACCURATE AEROSOL RETRIEVALS CAN ALSO BE OBTAINED IN BETWEEN BROKEN CLOUDS USING POLARIMETRY. FURTHERMORE THE RSP MEASURES IN SHORTWAVE INFRARED BANDS THAT PROVIDE TRADITIONAL RETRIEVALS OF CLOUD PARTICLE SIZES WHICH ALLOWS ADDRESSING THE CAMP2EX GOAL TO STUDY POTENTIAL PARTICLE SIZE BIASES OBTAINED WITH SUCH SHORTWAVE INFRARED MEASUREMENTS IN INHOMOGENEOUS CONDITIONS. RSP HAS FLOWN TWO PREVIOUS MISSIONS ON THE P3 AIRCRAFT SELECTED FOR CAMP2EX AND AN INTERFACE AND ALL CONNECTORS AND CABLES FOR THE INTEGRATION ARE READILY AVAILABLE LEADING TO MINIMAL INTEGRATION COSTS. IN ADDITION TO PROVIDING QUALITY-ASSURED LEVEL-1 AND OPERATIONAL LEVEL-2 PRODUCTS WE PROPOSE TO FURTHER DEVELOP AND EVALUATE SEVERAL OTHER PRODUCTS THAT ARE HIGHLY RELEVANT TO THE CAMP2EX OBJECTIVES. SPECIFICALLY PROPOSED ARE TECHNIQUES (1) TO ESTIMATE THE RELATIVE EXTINCTION OF LIQUID AND ICE IN MIXED-PHASE CLOUD TOPS; (2) TO REPRODUCE 2D SHAPES OF OBSERVED CUMULUS CLOUDS AND (3) TO RETRIEVE DROPLET SIZE PROFILES FROM SIDE VIEWS OF ISOLATED CLOUDS. TO AID THE DEVELOPMENT OF SUCH PRODUCTS AND TO EVALUATE RSP PRODUCTS IN GENERAL WE ALSO PROPOSE TO CONSTRUCT AN RSP MEASUREMENTS SIMULATOR BASED ON 3D RADIATIVE TRANSFER AND CLOUD MODEL OUTPUT. AS PART OF OUR INITIAL ANALYSIS OF THE RSP RETRIEVALS WE PROPOSE TO INVESTIGATE CORRELATIONS BETWEEN AEROSOL AND CLOUD PROPERTIES UNDER VARYING CONDITIONS WHICH COINCIDES WITH THE PRIMARY GOAL OF THE CAMP2EX CAMPAIGN., G4604829243, THE OVERALL SCIENTIFIC GOAL OF THE CLOUD AND AEROSOL MONSOONAL PROCESSES PHILIPPINES EXPERIMENT (CAMP2EX) IS TO CHARACTERIZE THE ROLE OF ANTHROPOGENIC AND NATURAL AEROSOLS IN MODULATING THE FREQUENCY AND AMOUNT OF WARM AND MIXED PHASE PRECIPITATION IN THE REGION OF THE PHILIPPINES DURING THE SOUTHWEST MONSOON. IT IS RECOGNIZED THAT SATELLITE OBSERVATIONS ARE CRITICAL TO ACHIEVING THIS GOAL. HOWEVER IT IS ALSO KNOW THAT THE COMPLEXITY OF THE ATMOSPHERE OVER THE REGION PARTICULARLY IN TERMS HETEROGENEITY IMPEDES THE USE OF SATELLITE DATA FOR QUANTIFYING AEROSOL-INDUCED CHANGES TO CLOUD AND PRECIPITATION PROPERTIES. THEREFORE ANOTHER PRIMARY GOAL OF CAMP2EX IS TO PROVIDE KEY CALIBRATION AND VALIDATION DATA FOR SATELLITE OBSERVATIONS FOR THE REGION. HERE WE PROPOSE TO CARRY OUT INVESTIGATIONS WITH OBJECTIVES THAT ARE ESSENTIAL FOR THE SUCCESS OF THE CAMP2EX FIELD CAMPAIGN SLATED FOR JULY-SEPTEMBER 2018. OUR ROLE IN THE PLANNING AND EXECUTION OF THE CAMP2EX CAMPAIGN IS AS FOLLOWS: (1) WE WILL DEVELOP AND DELIVER THE FIRST DETAILED REVIEW OF THE WEATHER AND CLIMATE OF THE PHILIPPINES AND ITS NEIGHBORING WATERS BASED ON EXISTING SATELLITE REANALYSIS AND IN SITU OBSERVATIONS USING AN APPROACH THAT NATURALLY PRESERVES THE MULTIVARIATE RELATIONSHIPS BETWEEN CLOUD AEROSOL AND PRECIPITATION AND THE DRIVING DYNAMICAL AND THERMODYNAMICAL PROPERTIES OF THE ATMOSPHERE; (2) WE WILL ANALYZE GEOSTATIONARY HIMAWARI-8/AHI SATELLITE DATA TO EVALUATE THE DIURNAL EVOLUTION OF CLOUDS AT HIGH RESOLUTION FOR THE PURPOSE OF FIELD AND FLIGHT PLANNING; (3) WE WILL CONTRIBUTE SUBSTANTIALLY TO THE FLIGHT PLANNING DOCUMENT BY COLLABORATING WITH SELECTED PIS AND THE PROJECT LEADERSHIP ENSURING THAT DATA COLLECTION IS HAD IN A MANNER THAT NOTE ONLY MEETS ALL SELECTED PIS OBJECTIVES BUT ALSO CAN ADDRESS THE NUMEROUS QUESTIONS DISCUSSED IN THE CAMP2EX WHITE PAPER QUESTIONS THAT MAY BE ADDRESSED BY INVESTIGATORS RESPONDING TO A FUTURE ROSES CALL FOR SCIENCE PROPOSALS; (4) WE WILL PARTICIPATE IN DRY RUN ACTIVITIES WITH THE CAMP2EX TEAM; (5) WE WILL HAVE AT LEAST ONE MEMBER OF OUR TEAM PARTICIPATE IN THE FIELD THROUGHOUT THE LENGTH OF THE CAMPAIGN WHERE WE CAN SERVE AS FLIGHT AND GROUND MISSION SCIENTISTS ASSIST WITH THE COORDINATION OF THE FLIGHTS WITH RELEVANT SATELLITE OVERPASSES AND ASSIST THE FORECASTING TEAM TO REVIEW THE WEATHER AND HELP INTERPRET NEAR-REAL TIME SATELLITE DATA; (6) WE WILL USE THE FIELD DATA TO EXAMINE THE QUALITY OF GPM AHI TERRA AND A-TRAIN DATASETS FOCUSING ON ISSUES OF SCENE HETEROGENEITY AND PRODUCT REPRESENTATIVENESS THAT HAVE YET TO BE ADDRESSED IN OTHER FIELD CAMPAIGNS AND WE WILL USE OUR FINDINGS TO HELP UNDERSTAND HOW THEY MAY INFLUENCE THE CLIMATOLOGY AND THE MULTIVARIATE RELATIONS HAD IN (1); (7) WE WILL EXAMINE THE SATELLITE REANALYSIS AND FIELD DATA FOR JULY-SEPTEMBER 2018 TO DEVELOP A PROJECT SUMMARY AND COMPARE IT TO THE CLIMATOLOGY WHICH IS NEEDED TO HELP PLACE CAMP2EX INTO A BROADER PERSPECTIVE; (8) WE WILL CARRY OUT AN INTEGRATIVE ANALYSIS INVOLVING MANY OF THE FIELD AND SATELLITE PRODUCTS TO EXAMINE MULTIVARIATE RELATIONSHIPS BETWEEN CLOUD AEROSOL AND PRECIPITATION AND THE DRIVING DYNAMICAL AND THERMODYNAMICAL PROPERTIES OF THE ATMOSPHERE INCLUDING A COMPARATIVE STUDY WITH PRIOR RESULTS WE OBTAINED OVER THE INDIAN OCEAN; AND FINALLY (9) WE WILL PROVIDE RESEARCH EXPERIENCE FOR A GRADUATE STUDENT IN USING BOTH REMOTE SENSING AND IN SITU DATA IN WEATHER AND CLIMATE RESEARCH. OUR RESEARCH NOT ONLY TAKES A LARGE STEP TOWARDS ACHIEVING THE OVERALL SCIENTIFIC GOAL OF CAMP2EX BUT ALSO PROVIDES IMPROVED ERROR CHARACTERIZATION DATA REPRESENTATIVENESS AND DATA SUMMARIES THAT PRESERVE THE MULTIVARIATE RELATIONSHIPS WITHIN OUR SATELLITE OBSERVATIONS. THIS WILL ENABLE OTHER CURRENT AND FUTURE SCIENTISTS TO TAKE FURTHER STEPS TOWARDS ACHIEVING THE OVERALL SCIENTIFIC GOAL OF CAMP2EX.
OpenAlex ID: W4385763379