Characterising Biomass Burning Aerosol in WRF-Chem using the Volatility Basis Set, with Evaluation against SAMBBA Flight Data

Tuesday, 15 December 2015: 17:30
3008 (Moscone West)
Douglas Lowe1, David O Topping1, Scott Archer-Nicholls2, Eoghan Darbyshire3, William Morgan1, Dantong Liu4, James D Allan4, Hugh Coe4 and Gordon McFiggans4, (1)University of Manchester, Manchester, M13, United Kingdom, (2)University Corporation for Atmospheric Research, Boulder, CO, United States, (3)University of Manchester, Manchester, United Kingdom, (4)University of Manchester, School of Earth, Atmospheric and Environmental Sciences, Manchester, United Kingdom
The burning of forests in the Amazonia region is a globally significant source of carbonaceous aerosol, containing both absorbing and scattering components [1]. In addition biomass burning aerosol (BBA) are also efficient cloud condensation nuclei (CCN), modifying cloud properties and influencing atmospheric circulation and precipitation tendencies [2]. The impacts of BBA are highly dependent on their size distribution and composition.

A bottom-up emissions inventory, the Brazilian Biomass Burning Emissions Model (3BEM) [3], utilising satellite products to generate daily fire emission maps is used. Injection of flaming emissions within the atmospheric column is simulated using both a sub-grid plume-rise parameterisation [4], and simpler schemes, within the Weather Research and Forecasting Model with Chemistry (WRF-Chem, v3.4.1) [5]. Aerosol dynamics are simulated using the sectional MOSAIC scheme [6], incorporating a volatility basis set (VBS) treatment of organic aerosol [7]. For this work we have modified the 9-bin VBS to use the biomass burning specific scheme developed by May et al. [8].

The model has been run for September 2012 over South America (at a 25km resolution). We will present model results evaluating the modelled aerosol vertical distribution, size distribution, and composition against measurements taken by the FAAM BAe-146 research aircraft during the SAMBBA campaign. The main focus will be on investigating the factors controlling the vertical gradient of the organic mass to black carbon ratio of the measured aerosol.

This work is supported by the Nature Environment Research Council (NERC) as part of the SAMBBA project under grant NE/J010073/1.

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[2] M. O. Andreae et al., 2004, Science, 303, 1337-1342.

[3] K. Longo et al., 2010, Atmos. Chem. Phys., 10, 5,785-5,795.

[4] S. Freitas et al., 2007, Atmos. Chem. Phys., 7, 3,385-3,398.

[5] S. Archer-Nicholls et al., 2015, Geosci. Model Dev., 8, 549-577

[6] R. Zavari et al., 2008, J. Geophys. Res., 113, D132024.

[7] M. Shrivastava et al., 2011, Atmos. Chem. Phys., 11, 6639-6662

[8] A. May et al., 2013, J. Geophys. Res., 118, 11,327-11,338