Carbonaceous aerosols

Overview

From Park et al, 2003:

The simulation of carbonaceous aerosols in GEOS-Chem follows that of the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model [Chin et al., 2002], with a number of modifications described below. The model resolves EC and OC, with a hydrophobic and a hydrophilic fraction for each (i.e., four aerosol types). Combustion sources emit hydrophobic aerosols that then become hydrophilic with an e-folding time of 1.2 days following Cooke et al. [1999] and Chin et al. [2002]. We assume that 80% of EC and 50% of OC emitted from all primary sources are hydrophobic [Cooke et al., 1999; Chin et al., 2002; Chung and Seinfeld, 2002]. All secondary OC is assumed to be hydrophilic. The four aerosol types in the model are further resolved into contributions from fossil fuel, biofuel, and biomass burning, plus an OC component of biogenic origin, resulting in a total of 13 tracers transported by the model.

Simulation of aerosol wet and dry deposition follows the schemes used by Liu et al. [2001] in previous GEOS-Chem simulations of 210Pb and 7Be aerosol tracers. Wet deposition includes contributions from scavenging in convective updrafts, rainout from convective anvils, and rainout and washout from large-scale precipitation. Wet deposition is applied only to the hydrophilic component of the aerosol. Dry deposition of aerosols uses a resistance-in-series model [Walcek et al., 1986] dependent on local surface type and meteorological conditions; it is small compared to wet deposition. Liu et al. [2001] found no systematic biases in their simulations of 210Pb and 7Be with GEOS-Chem.

We use global anthropogenic emissions of EC (6.4 Tg year1) and OC (10.5 Tg year1) from the gridded Cooke et al. [1999] inventory for 1984.... Cooke et al. [1999] do not resolve the contributions to EC and OC emissions from heating fuel. We assume these contributions to represent 8% (EC) and 35% (OC) of total anthropogenic emissions, based on data for the Pittsburgh area from Cabada et al. [2002] and apply local seasonal variations of emissions using the heating degree days approach [Energy Information Administration (EIA), 1997; Cabada et al., 2002]. In this manner we find that anthropogenic EC emission in the United States in winter is 15% higher than in summer. For OC the anthropogenic winter emission is twice that in summer.

Biomass burning emissions of EC and OC are calculated using the global biomass burning inventory of Duncan et al. [2003].

Secondary formation of OC from oxidation of large hydrocarbons is an important source but uncertainties are large [Griffin et al., 1999; Kanakidou et al., 2000; Chung and Seinfeld, 2002]. Chung and Seinfeld [2002] find that biogenic terpenes are the main source of secondary OC aerosols. We assume a 10% carbon yield of OC from terpenes [Chin et al., 2002], and apply this yield to a global terpene emission inventory dependent on vegetation type, monthly adjusted leaf area index, and temperature [Guenther et al., 1995].

Validation

See Park et al, 2003.

References

1. Bey, I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J. Mickley, and M. Schultz, Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073–23,096, 2001.
2. Cabada, J. C., S. N. Pandis, and A. L. Robinson, Sources of atmospheric carbonaceous particulate matter in Pittsburgh, Pennsylvania, J. Air Waste Manage. Assoc., 52, 732–741, 2002.
3. Chin, M., P. Ginoux, S. Kinne, O. Torres, B. Holben, B. N. Duncan, R. V. Martin, J. A. Logan, A. Higurashi, and T. Nakajima, Tropospheric aerosol optical thickness from the GOCART model and comparisons with satellite and sunphotometer measurements, J. Atmos. Sci., 59, 461–483, 2002.
4. Chung, S. H., and J. H. Seinfeld, Global distribution and climate forcing of carbonaceous aerosols, J. Geophys. Res., 107(D19), 4407, doi:10.1029/2001JD001397, 2002.
5. Cooke, W. F., C. Liousse, H. Cachier, and J. Feichter, Construction of a 1° x 1° fossil fuel emission data set for carbonaceous aerosol and implementation and radiative impact in the ECHAM-4 model, J. Geophys. Res., 104, 22,137–22,162, 1999.
6. Duncan, B. N., R. V. Martin, A. C. Staudt, R. Yevich, and J. A. Logan, Interannual and seasonal variability of biomass burning emissions constrained by satellite observations, J. Geophys. Res., 108(D2), 4100, doi:10.1029/2002JD002378, 2003.
7. Energy Information Administration (EIA), State Energy Data Report 1999, Washington, D. C., 2001.
8. Griffin, R. J., D. Dabdub III, and J. H. Seinfeld, Estimate of global atmospheric organic aerosol from oxidation of biogenic hydrocarbons, Geophys. Res. Lett., 26, 2721– 2724, 1999.
9. Guenther, A., et al., A global model of natural volatile organic compound emission, J. Geophys. Res., 100, 8873–8892, 1995.
10. Kanakidou, M., K. Tsigaridis, F. J. Dentener, and P. J. Crutzen, Humanactivity-enhanced formation of organic aerosols by biogenic hydrocarbon oxidation, J. Geophys. Res., 105, 9243–9254, 2000.
11. Liu, H., D. J. Jacob, I. Bey, and R. M. Yantosca, Constraints from 210Pb and 7Be on wet deposition and transport in a global three-dimensional chemical tracer model driven by assimilated meteorological fields, J. Geophys. Res., 106, 12,109–12,128, 2001.
12. Walcek, C. J., R. A. Brost, and J. S. Chang, SO2, sulfate and HNO3 deposition velocities computed using regional landuse and meteorological data, Atmos. Environ., 20, 949–964, 1986.

--Bob Y. 11:09, 22 February 2010 (EST)