Black Carbon Aerosols in the Marine Boundary Layer on the West Coast of Southern Africa
Abstract
Continuous measurements, since 2012, at the Henties Bay Aerosol Observatory (HBAO; 22°S, 14°05'E), Namibia, show that, during the austral wintertime, transport of black carbon aerosols occurs at low-level into the marine boundary layer towards the South East Atlantic coast. This is ahead of the dry season peak for southern Africa (August to October), when biomass burning aerosols outflow into the free troposphere above the stratocumulus clouds. The concentration of black carbon equivalent associated with this low-level transport is of the order of 100-150 ng m-3. Assuming that they are related to biomass burning, a particle mass concentration of 5-7 µg m-3 and to a number concentration of 300-400 cm-3 is estimated. These values are sufficiently high to enable them, by entrainment, to cause an almost doubling of the cloud optical depth as well as an increase of approximately 40% in cloud reflectivity with respect to pristine conditions. Their direct radiative effect is negligible.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A33L..03P
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3360 Remote sensing;
- ATMOSPHERIC PROCESSES