Sensitivity of global cloud condensation nuclei concentrations to primary sulfate emission parameterizations

• Main Authors: G. Luo, F. Yu
• Format: Article
• Language: English
• Published: Copernicus Publications 2011-03-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/11/1949/2011/acp-11-1949-2011.pdf

The impact of primary sulfate emissions on cloud condensation nuclei (CCN) concentrations, one of the major uncertainties in global CCN predictions, depends on the fraction of sulfur mass emitted as primary sulfate particles (<i>f</i>_sulfate), the fraction of primary sulfate mass distributed into the nucleation mode particles (<i>f</i>_nucl), and the nucleation and growth processes in the ambient atmosphere. Here, we use a global size-resolved aerosol microphysics model recently developed to study how the different parameterizations of primary sulfate emission affect particle properties and CCN abundance. Different from previous studies, we use the ion-mediated nucleation scheme to simulate tropospheric particle formation. The kinetic condensation of low volatile secondary organic gas (SOG) (in addition to H₂SO₄ gas) on nucleated particles is calculated based on our new scheme that considers the SOG volatility changes arising from the oxidation aging. Our simulations show a compensation effect of nucleation to primary sulfate emission. We find that the change of <i>f</i>_nucl from 5% to 15% has a more significant impact on the simulated particle number budget than that of <i>f</i>_sulfate within the range of 2.5–5%. Based on our model configurations, an increase of <i>f</i>_sulfate from 0% to 2.5% (with <i>f</i>_nucl = 5%) does not improve the agreement between simulated and observed annual mean number concentrations of particles >10 nm at 21 stations but further increase of either <i>f</i>_sulfate from 2.5% to 5% (with <i>f</i>_nucl = 5%) or <i>f</i>_nucl from 5% to 15% (with <i>f</i>_sulfate = 2.5%) substantially deteriorates the agreement. For <i>f</i>_sulfate of 2.5%–5% and <i>f</i>_nucl of 5%, our simulations indicate that the global CCN at supersaturation of 0.2% increases by 8–11% in the boundary layer and 3–5% in the whole troposphere (compared to the case with <i>f</i>_sulfate=0).