A dynamic aerosol module for global chemical transport models: Model description

Herzog, Michael

doi:10.1029/2003jd004405

Cited by 57 publications

(60 citation statements)

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“…In this context, the numerical methods used for the H 2 SO 4 processes will possibly be refined. Time integration schemes with adaptive step size and dynamical error control, such as those used by Herzog et al (2004) and Zaveri et al (2008) will be considered.…”

Section: Sulfuric Acid Gas and Aerosol Nucleationmentioning

confidence: 99%

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

et al. 2012

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Abstract. This paper introduces and evaluates the second version of the global aerosol-climate model ECHAM-HAM. Major changes have been brought into the model, including new parameterizations for aerosol nucleation and water uptake, an explicit treatment of secondary organic aerosols, modified emission calculations for sea salt and mineral dust, the coupling of aerosol microphysics to a two-moment stratiform cloud microphysics scheme, and alternative wet scavenging parameterizations. These revisions extend the model's capability to represent details of the aerosol lifecycle and its interaction with climate. Nudged simulations of the year 2000 are carried out to compare the aerosol properties and global distribution in HAM1 and HAM2, and to evaluate them against various observations. Sensitivity experiments are performed to help identify the impact of each individual update in model formulation.Results indicate that from HAM1 to HAM2 there is a marked weakening of aerosol water uptake in the lower troposphere, reducing the total aerosol water burden from 75 Tg to 51 Tg. The main reason is the newly introduced κ-Köhler-theory-based water uptake scheme uses a lower value for the maximum relative humidity cutoff. Particulate organic matter loading in HAM2 is considerably higher in the upper troposphere, because the explicit treatment of secondary organic aerosols allows highly volatile oxidation products of the precursors to be vertically transported to regions of very low temperature and to form aerosols there. Sulfate, black carbon, particulate organic matter and mineral dust in HAM2 have longer lifetimes than in HAM1 because of weaker incloud scavenging, which is in turn related to lower autoconversion efficiency in the newly introduced two-moment cloud microphysics scheme. Modification in the sea salt emission scheme causes a significant increase in the ratio (from 1.6 to 7.7) between accumulation mode and coarse mode emission fluxes of aerosol number concentration. This leads to a general increase in the number concentration of smaller particles over the oceans in HAM2, as reflected by the higher Angström parameters.Evaluation against observation reveals that in terms of model performance, main improvements in HAM2 include a marked decrease of the systematic negative bias in the absorption aerosol optical depth, as well as smaller biases over the oceans inÅngström parameter and in the accumulation mode number concentration. The simulated geographical distribution of aerosol optical depth (AOD) is better correlated with the MODIS data, while the surface aerosol mass concentrations are very similar to those in the old version. The total aerosol water content in HAM2 is considerably Published by Copernicus Publications on behalf of the European Geosciences Union. K. Zhang et al.: Aerosol properties in ECHAM-HAM2closer to the multi-model average from Phase I of the AeroCom intercomparison project. Model deficiencies that require further efforts in the future include (i) positive biases in AOD over the ocean, (ii) n...

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Section: Sulfuric Acid Gas and Aerosol Nucleationmentioning

confidence: 99%

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

et al. 2012

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“…To our knowledge, momentbased approaches have not been implemented into global models for the purposes of predicting CCN concentrations although regional-scale applications have been demonstrated (Yu et al, 2003). Modal algorithms that represent the aerosol size distribution as the sum of several lognormal distributions, each characterized by a number concentration, median diameter, and geometric standard deviation, have been developed by Herzog et al (2004), Jung et al (2004) and Vignati et al (2004) and implemented in Easter et al (2004), Ghan et al (2001), Stier et al (2005) and Wilson et al (2001) in global models. Except for Jung et al (2004), the versions of the modal approach cited here have prescribed constant values to the geometric standard deviations such that only two of the three lognormal parameters are predicted variables.…”

Section: Introductionmentioning

confidence: 99%

Contribution of primary carbonaceous aerosol to cloud condensation nuclei: processes and uncertainties evaluated with a global aerosol microphysics model

2007

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Abstract. This paper explores the impacts of primary carbonaceous aerosol on cloud condensation nuclei (CCN) concentrations in a global climate model with size-resolved aerosol microphysics. Organic matter (OM) and elemental carbon (EC) from two emissions inventories were incorporated into a preexisting model with sulfate and seasalt aerosol. The addition of primary carbonaceous aerosol increased CCN(0.2%) concentrations by 65-90% in the globally averaged surface layer depending on the carbonaceous emissions inventory used. Sensitivity studies were performed to determine the relative importance of organic solubility/hygroscopicity in predicting CCN. In a sensitivity study where carbonaceous aerosol was assumed to be completely insoluble, concentrations of CCN(0.2%) still increased by 40-50% globally over the no carbonaceous simulation because primary carbonaceous emissions were able to become CCN via condensation of sulfuric acid. This shows that approximately half of the contribution of primary carbonaceous particles to CCN in our model comes from the addition of new particles (seeding effect) and half from the contribution of organic solute (solute effect). The solute effect tends to dominate more in areas where there is less inorganic aerosol than organic aerosol and the seeding effect tends to dominate in areas where there is more inorganic aerosol than organic aerosol. It was found that an accurate simulation of the number size distribution is necessary to predict the CCN concentration but assuming an average chemical composition will generally give a CCN concentration within a factor of 2. If a "typical" size distribution is assumed for each species when calculating CCN, such as is done in bulk aerosol models, the mean error relative to a simulation with size resolved microphysics is on the order of 35%. Predicted values of carbonaceous aerosol mass Correspondence to: J. R. Pierce (jrpierce@andrew.cmu.edu) and aerosol number were compared to observations and the model showed average errors of a factor of 3 for carbonaceous mass and a factor of 4 for total aerosol number; however, errors in the accumulation mode concentrations were found to be lower in comparisons with European and marine observations.. The errors in CN and carbonaceous mass may be reduced by improving the emission size distributions of both primary sulfate and primary carbonaceous aerosol.

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“…be simplified. The aerosol distribution in aerosol modules is described in most cases using the bulk approach (Liao and Seinfeld, 2005;Liu et al, 2005;Reddy et al, 2005;, modal approach (Ghan et al, 2001;Wilson et al, 2001;Herzog et al, 2004;Vignati et al, 2004;Lauer et al, 2005;Stier et al, 2005), and sectional approach (Weisenstein et al, 1997;Jacobson, 2001;Timmreck, 2001;Rodriguez and Dabdub, 2004;Spracklen et al, 2005;Hommel, 2008;Kokkola et al, 2008). In the bulk approach, only the aerosol mass is prognostic.…”

Section: Introductionmentioning

confidence: 99%

Aerosol microphysics modules in the framework of the ECHAM5 climate model – intercomparison under stratospheric conditions

et al. 2009

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Abstract. In this manuscript, we present an intercomparison of three different aerosol microphysics modules that are implemented in the climate model ECHAM5. The comparison was done between the modal aerosol microphysics module M7, which is currently the default aerosol microphysical core in ECHAM5, and two sectional aerosol microphysics modules SALSA, and SAM2. The detailed aerosol microphysical model MAIA was used as a reference to evaluate the results of the aerosol microphysics modules with respect to sulphate aerosol.The ability of the modules to describe the development of the aerosol size distribution was tested in a zero dimensional framework. We evaluated the strengths and weaknesses of different approaches under different types of stratospheric conditions. Also, we present an improved method for the time integration in M7 and study how the setup of the modal aerosol modules affects the evolution of the aerosol size distribution.Intercomparison simulations were carried out with varying SO 2 concentrations from background conditions to extreme values arising from stratospheric injections by large volcanic eruptions. Under background conditions, all microphysics modules were in good agreement describing the shape of the aerosol size distribution, but the scatter between the model results increased with increasing SO 2 concentrations. In particular in the volcanic case the setups of the aerosol modules have to be adapted in order to dependably capture the evoluCorrespondence to: H. Kokkola (harri.kokkola@fmi.fi) tion of the aerosol size distribution, and to perform in global model simulations.In summary, this intercomparison serves as a review of the different aerosol microphysics modules which are currently available for the climate model ECHAM5.

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A dynamic aerosol module for global chemical transport models: Model description

Cited by 57 publications

References 50 publications

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

The global aerosol-climate model ECHAM-HAM, version 2: sensitivity to improvements in process representations

Contribution of primary carbonaceous aerosol to cloud condensation nuclei: processes and uncertainties evaluated with a global aerosol microphysics model

Aerosol microphysics modules in the framework of the ECHAM5 climate model – intercomparison under stratospheric conditions

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