La Nina Climate Response to South African Biomass Burning Aerosols
Abstract
The climate response to atmospheric aerosols remains highly uncertain, including their effects on dominant modes of climate variability like El Nino Southern Oscillation (ENSO). This is due to several sources of uncertainty, including aerosol emission, transport, removal, vertical distribution, and radiative properties. Here, we conduct coupled ocean atmosphere simulations with the Community Earth System Model (CESM) driven by the direct radiative effects of semi-empirical fine-mode aerosol forcing without dust and sea salt. Despite small aerosol forcing in the tropical Pacific, a La Nina-like climate response develops, including strengthening of the tropical Pacific Walker Circulation. Additional simulations show that this response is related to south African biomass burning aerosol, which locally warms the atmospheric column and drives anomalous ascent and upper-level divergence. The anomalous heating triggers an atmospheric teleconnection to the tropical Pacific, including upper level convergence and subsidence in the eastern tropical Pacific. Observations also support a relationship between south African biomass burning emissions and ENSO, with La Nina events preceding strong south African biomass burning in boreal fall. Our simulations suggest a possible two-way feedback between ENSO and south African biomass burning, with La Nina promoting more biomass burning emissions, which may then strengthen the developing La Nina.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A51S2881A
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0320 Cloud physics and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0321 Cloud/radiation interaction;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3354 Precipitation;
- ATMOSPHERIC PROCESSES