A global off-line model of size-resolved aerosol microphysics: II. Identification of key uncertainties

Spracklen, D. V.; Pringle, K. J.; Carslaw, K. S.; Chipperfield, M. P.; Mann, G. W.

doi:10.5194/acpd-5-3437-2005

Cited by 32 publications

(46 citation statements)

References 34 publications

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“…The noncontinuum effect that occurs during condensation onto small particles is accounted for using a correction factor which is a function of the Knudsen number. The accommodation coefficient, a e , is assumed to have a value of unity, although the sensitivity of the aerosol distribution to the magnitude of a e is explored in Spracklen et al (2005).…”

Section: Microphysical Processesmentioning

confidence: 99%

“…Adams and Seinfeld (2002) simulate this source of particles by including 3% of anthropogenic sulfur emissions directly as particles. This mechanism is discussed further in Spracklen et al (2005).…”

Section: Global Cn and Ccn Distributionsmentioning

confidence: 99%

“…This first paper describes the model and the global simulations of aerosol properties, including a basic level of model evaluation. The second paper (Spracklen et al, 2005) examines in detail the sensitivity of the predicted aerosol size distribution to uncertainties in the driving microphysical processes. The third paper, in preparation, will present a detailed comparison of the model against aerosol observations.…”

Section: Introductionmentioning

confidence: 99%

“…Anthropogenic emissions are taken from the Global Emissions Inventory Activity (GEIA) database (Benkovitz et al, 1996), which are seasonally averaged and based on the year 1985. In the baseline model runs presented here all the emitted sulfur is assumed to be SO 2 , but in Spracklen et al (2005) we also explore the sensitivity of modelled aerosol to small amounts of primary sulfate aerosol. The emissions inventory classifies emissions as occurring above or below 100 m. The emissions are partitioned linearly onto the appropriate model grid levels according to the thickness of the model levels.…”

Section: Gas Phase Chemistry and Emissionsmentioning

confidence: 99%

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A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties

et al. 2005

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Abstract.A GLObal Model of Aerosol Processes (GLOMAP) has been developed as an extension to the TOMCAT 3-D Eulerian off-line chemical transport model. GLOMAP simulates the evolution of the global aerosol size distribution using a sectional two-moment scheme and includes the processes of aerosol nucleation, condensation, growth, coagulation, wet and dry deposition and cloud processing. We describe the results of a global simulation of sulfuric acid and sea spray aerosol. The model captures features of the aerosol size distribution that are well established from observations in the marine boundary layer and free troposphere. Modelled condensation nuclei (CN >3 nm) vary between about 250-500 cm −3 in remote marine boundary layer regions and are generally in good agreement with observations. Modelled continental CN concentrations are lower than observed, which may be due to lack of some primary aerosol sources or the neglect of nucleation mechanisms other than binary homogeneous nucleation of sulfuric acidwater particles. Remote marine CN concentrations increase to around 2000-10 000 cm −3 (at standard temperature and pressure) in the upper troposphere, which agrees with typical observed vertical profiles. Cloud condensation nuclei (CCN) at 0.2% supersaturation vary between about 1000 cm −3 in polluted regions and between 10 and 500 cm −3 in the remote marine boundary layer. New particle formation through sulfuric acid-water binary nucleation occurs predominantly in the upper troposphere, but the model results show that these particles contribute greatly to aerosol concentrations in the marine boundary layer. For this sulfur-sea salt system it is estimated that sea spray emissions account for only ∼10% of CCN in the tropical marine boundary layer, but between 20 and 75% in the mid-latitude Southern Ocean. In a run with only natural sulfate and sea salt emissions the global mean surface CN concentration is more than 60% of that from a run Correspondence to: D. V. Spracklen (dominick@env.leeds.ac.uk) with 1985 anthropogenic sulfur emissions, although the natural emissions comprise only 27% of total sulfur emissions. Southern hemisphere marine boundary layer CN are more than 90% natural in origin, while polluted continental CN are more than 90% anthropogenic in origin, although these numbers will change when other anthropogenic CN sources are included in the model.

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Section: Microphysical Processesmentioning

confidence: 99%

Section: Global Cn and Ccn Distributionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Gas Phase Chemistry and Emissionsmentioning

confidence: 99%

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A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties

et al. 2005

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“…For example, Adams and Seinfeld (2003) showed that a few percent of anthropogenic sulfur emitted as particulate sulfate (to represent the sub-grid nucleation process) increases CCN concentrations in polluted areas by up to ∼200-500%. Spracklen et al (2005b) showed that global mean sulfate and sea salt derived CCN concentrations change by up to 27% in marine boundary layer and by more than 100% over some continental regions when the fraction of anthropogenic SO 2 emitted as particulates is increased from 0 to 5%. Pierce et al (2007) showed that the inclusion of carbonaceous aerosol particles (assumed to have number median diameter of ∼25 nm) can increase CCN concentrations (0.2%) by 65-90% in the globally averaged surface layer.…”

Section: Introductionmentioning

confidence: 99%

Simulation of particle size distribution with a global aerosol model: contribution of nucleation to aerosol and CCN number concentrations

2009

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Abstract. An advanced particle microphysics model with a number of computationally efficient schemes has been incorporated into a global chemistry transport model (GEOSChem) to simulate particle number size distributions and cloud condensation nuclei (CCN) concentrations in the atmosphere. Size-resolved microphysics for secondary particles (i.e., those formed from gaseous species) and sea salt has been treated in the present study. The growth of nucleated particles through the condensation of sulfuric acid vapor and equilibrium uptake of nitrate, ammonium, and secondary organic aerosol is explicitly simulated, along with the scavenging of secondary particles by primary particles (dust, black carbon, organic carbon, and sea salt). We calculate secondary particle formation rate based on ion-mediated nucleation (IMN) mechanism and constrain the parameterizations of primary particle emissions with various observations. Our simulations indicate that secondary particles formed via IMN appear to be able to account for the particle number concentrations observed in many parts of the troposphere. A comparison of the simulated annual mean concentrations of condensation nuclei larger than 10 nm (CN10) with those measured values show very good agreement (within a factor of two) in near all 22 sites around the globe that have at least one full year of CN10 measurements. Secondary particles appear to dominate the number abundance in most parts of the troposphere. Calculated CCN concentration at supersaturation of 0.4% (CCN0.4) and the fraction of CCN0.4 that is secondary (f sec CCN ) have large spatial variations. Over the middle latitude in the Northern Hemisphere, zonally averaged CCN0.4 decreases from ∼400-700 cm −3 in the boundary layer (BL) to below 100 cm −3 above altitude of ∼4 km, the correspondCorrespondence to: F. Yu (yfq@asrc.cestm.albany.edu) ing f sec CCN values change from 50-60% to above ∼70%. In the Southern Hemisphere, the zonally averaged CCN0.4 is below 200 cm −3 and f sec CCN is generally above 60% except in the BL over the Southern Ocean.

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Estimation of global black carbon direct radiative forcing and its uncertainty constrained by observations

et al. 2016

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Black carbon (BC) contributes to global warming by absorbing sunlight. However, the size of this contribution, namely, the direct radiative forcing (RF), ranges from +0.1 to +1.0 W m À2 , largely due to differences between bottom-up and observation-based estimates. Current global models systematically underestimate BC radiation absorption relative to observations, which is often attributed to the underestimation of BC emissions. Several studies that adjusted emissions to correct biases of global aerosol models resulted in a revised upward estimate of the BC RF. However, the BC RF was never optimized against observations in a rigorous mathematical manner. Here we simulated the absorption of solar radiation by BC from all sources at the 10 km resolution by combining a highly disaggregated emission inventory with a nested aerosol climate model and a downscaling method. As a result, the normalized mean bias in BC radiation absorption was reduced from À51% to À24% in Asia and from À57% to À50% elsewhere. We applied a Bayesian method that makes the best account of all model, representativeness and observational uncertainties to estimate the BC RF and its uncertainty. Using the new emission inventory and high-resolution model reduces uncertainty in BC RF from À101%/+152% to À70%/+71% over Asia and from À83%/+108% to À64%/+68% over other continental regions. Finally we derived an observationally constrained BC RF of 0.61 Wm À2 (0.16 to 1.40 as 90% confidence) as our best estimate. Our estimate implies that reduction in BC emissions would contribute to slow down global warming, but the contribution could be less than previously thought. tions of aerosol absorption optical depth (AAOD) from the ground-based remote sensing Aerosol Robotic Network (AERONET) [Koch et al., 2009;Bond et al., 2013], leading to ad hoc adjustments in the so-called observation-based or top-down method. Previous studies chose to adjust the BC emissions upward to correct the low bias of global models, resulting in a larger revised BC RF [Sato et al., 2003;Chung et al., 2005Chung et al., , 2012Ramanathan and Carmichael, 2008;Bond et al., 2013], in the range 0.6-1.0 W m À2 . This would make BC a WANG ET AL.RADIATIVE FORCING OF BLACK CARBON 5948

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A global off-line model of size-resolved aerosol microphysics: II. Identification of key uncertainties

Cited by 32 publications

References 34 publications

A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties

A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties

Simulation of particle size distribution with a global aerosol model: contribution of nucleation to aerosol and CCN number concentrations

Estimation of global black carbon direct radiative forcing and its uncertainty constrained by observations

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