Impact of Black Carbon Aerosol on Climate in East Asia
Abstract
Black carbon (BC) is one of the major atmospheric aerosols, which affects the radiative balance and thus the climate. We examine the effects of BC aerosol on climate in East Asia using a global 3-D chemical transport model (GEOS-Chem) driven by assimilated meteorological data and the National Center for Atmospheric Research Column Radiation Model (NCAR-CRM). Simulated BC aerosol concentrations are compared with observations from the Transport and Chemical Evolution over the Pacific (TRACE- P) and the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) aircraft campaigns in spring 2001. The model captured observed vertical distributions in East Asia. We applied our simulated BC aerosol with typical optical properties (refractive index (N) = 1.75-0.45i at a wavelength of 550 nm) to the NCAR-CRM to compute radiative forcing of BC aerosol. Our calculation shows negative forcing at the surface and positive forcing at the top of the atmosphere in East Asia, indicating warming of the atmosphere. A recent study by Alexander et al. (2008) found that submicrometer amorphous carbon spheres are ubiquitous in East Asian-Pacific outflow, and these carbon spheres are brown, not black, with a refractive index of 1.67-0.27i at a wavelength of 550 nm. In order to accommodate these new findings we also calculate radiative forcing of the simulated BC assuming its half as brown carbon in the NCAR-CRM. Our new values of simulated optical depth and resulting radiative forcing are by 50% lower than the previous results, implying a possible overestimation of BC warming effect in East Asia.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMGC53B0722K
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801;
- 4906);
- 1807 Climate impacts;
- 6060 Radiation and chemistry