Tropospheric aerosol microphysics simulation with assimilated meteorology: model description and intermodel comparison

W. Trivitayanurak (1) , P. J. Adams (1, 2) , D. V. Spracklen (3) , K. S. Carslaw (4)

1 Department of Civil and Environmental Engineering [Pittsburgh]
2 Department of Engineering and Public Policy
3 SEAS - Harvard John A. Paulson School of Engineering and Applied Sciences
4 Institute for Atmospheric Science [Leeds]

We implement the TwO-Moment Aerosol Sectional (TOMAS) microphysics module into GEOS-CHEM, a CTM driven by assimilated meteorology. TOMAS has 30 size sections covering 0.01?10 ?m diameter with conservation equations for both aerosol mass and number. The implementation enables GEOS-CHEM to simulate aerosol microphysics, size distributions, mass and number concentrations. The model system is developed for sulfate and sea-salt aerosols, a year-long simulation has been performed, and results are compared to observations. Additionally model intercomparison was carried out involving global models with sectional microphysics: GISS GCM-II' and GLOMAP. Comparison with marine boundary layer observations of CN and CCN(0.2%) shows that all models perform well with average errors of 30?50%. However, all models underpredict CN by up to 42% between 15° S and 45° S while overpredicting CN up to 52% between 45° N and 60° N, which could be due to the sea-salt emission parameterization and the assumed size distribution of primary sulfate emission, in each case respectively. Model intercomparison at the surface shows that GISS GCM-II' and GLOMAP, each compared against GEOS-CHEM, both predict 40% higher CN and predict 20% and 30% higher CCN(0.2%) on average, respectively. Major discrepancies are due to different emission inventories and transport. Budget comparison shows GEOS-CHEM predicts the lowest global CCN(0.2%) due to microphysical growth being a factor of 2 lower than other models because of lower SO₂ availability. These findings stress the need for accurate meteorological inputs and updated emission inventories when evaluating global aerosol microphysics models.

Domaines: Océan, Atmosphère

W. Trivitayanurak, P. J. Adams, D. V. Spracklen, K. S. Carslaw. Tropospheric aerosol microphysics simulation with assimilated meteorology: model description and intermodel comparison. Atmospheric Chemistry and Physics Discussions, 2007, 7 (5), pp.14369-14411. ⟨hal-00303126⟩