Measurement report: Characterization of aerosol hygroscopicity over Southeast Asia during the NASA CAMP<sup>2</sup>Ex campaign
<p>This study characterizes the spatial and vertical nature of aerosol hygroscopicity in Southeast Asia and relates it to aerosol composition and sources. Aerosol hygroscopicity via the light scattering hygroscopic growth factor, <span class="inline-formula"><i>f</i>...
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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/5469/2025/acp-25-5469-2025.pdf |
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| Summary: | <p>This study characterizes the spatial and vertical nature of aerosol hygroscopicity in Southeast Asia and relates it to aerosol composition and sources. Aerosol hygroscopicity via the light scattering hygroscopic growth factor, <span class="inline-formula"><i>f</i></span>(RH), is calculated from the amplification of PM<span class="inline-formula"><sub>5</sub></span> (particulate matter with a particle diameter, <span class="inline-formula"><i>D</i><sub>p</sub></span>, <span class="inline-formula"><5</span> <span class="inline-formula">µ</span>m) scattering measurements from <span class="inline-formula"><40</span> % to 82 % relative humidity during the Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP<span class="inline-formula"><sup>2</sup></span>Ex) between August and October 2019 over the northwest tropical Pacific. Median <span class="inline-formula"><i>f</i></span>(RH) is low (1.26 with lower to upper quartiles of 1.05 to 1.43) like polluted environments, due to the dominance of the mixture of organic carbon and elemental carbon. The <span class="inline-formula"><i>f</i></span>(RH) is lowest due to smoke from the Maritime Continent (MC) during its peak biomass burning season, coincident with high carbon monoxide concentrations (<span class="inline-formula">>0.25</span> ppm) and pronounced levels of accumulation-mode particles and organic mass fractions. The highest <span class="inline-formula"><i>f</i></span>(RH) values are linked to coarser particles from the West Pacific and aged biomass burning particles in the region farthest away from the MC, where <span class="inline-formula"><i>f</i></span>(RH) values are lower than typical polluted marine environments. Convective transport and associated cloud processing in these regions decrease and increase hygroscopicity aloft in cases with transported air masses exhibiting increased organic and sulfate mass fractions, respectively. An evaluation of the Community Atmosphere Model with Chemistry (CAM-chem) for cases of vertical transport showed the underrepresentation of organics, resulting in overestimated modeled aerosol hygroscopicity. These findings on aerosol hygroscopicity can help to improve aerosol representation in models and the understanding of cloud formation.</p> |
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| ISSN: | 1680-7316 1680-7324 |