Cloud condensation nuclei properties of South Asian outflow over the northern Indian Ocean during winter
<p>Extensive measurements of cloud condensation nuclei (CCN) and condensation nuclei (CN) concentrations in the South Asian outflow to the northern Indian Ocean were carried out on board an instrumented research vessel, as part of the Integrated Campaign for Aerosols, gases and Radiation Budge...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/3135/2020/acp-20-3135-2020.pdf |
| Summary: | <p>Extensive measurements of cloud condensation nuclei (CCN)
and condensation nuclei (CN) concentrations in the South Asian outflow to
the northern Indian Ocean were carried out on board an instrumented research
vessel, as part of the Integrated Campaign for Aerosols, gases and Radiation
Budget (ICARB) during the winter season (January–February 2018).
Measurements include a north–south transect across the South Asian plume
over the northern Indian Ocean and an east–west transect over the equatorial
Indian Ocean (<span class="inline-formula">∼2</span><span class="inline-formula"><sup>∘</sup></span> S), which is far away from the
continental sources. South Asian outflow over the northern Indian Ocean is
characterized by the high values of CCN number concentration
(<span class="inline-formula">∼5000</span> cm<span class="inline-formula"><sup>−3</sup></span>), low CCN activation efficiency
(<span class="inline-formula">∼25</span> %) and a steep increase in CCN concentration with the
increase in supersaturation. In contrast, low CCN concentration
(<span class="inline-formula">∼1000</span> cm<span class="inline-formula"><sup>−3</sup></span>) with flat supersaturation spectra was found
over the equatorial Indian Ocean. The CCN properties exhibited significant
dependence on the geometric mean diameter (GMD) of the aerosol number size
distribution, and CCN activation efficiency decreased to low values
(<span class="inline-formula"><20</span> %) at the time of new-particle formation events over
near-coastal and remote oceanic regions. The analysis of the activation
efficiencies for the “similar” aerosol size distributions over the northern
Indian Ocean indicated the primary role of aerosol number size distribution
on CCN activation efficiency. The dependence of CCN properties and
activation efficiency on size-segregated aerosol number concentration,
especially during the ultrafine (<span class="inline-formula"><100</span> nm) particle events, is
investigated in detail for the first time over the region.</p> |
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| ISSN: | 1680-7316 1680-7324 |