Simulating aerosol microphysics with the ECHAM/MADE GCM – Part I: Model description and comparison with observations

Abstract

Abstract. The aerosol dynamics module MADE has been coupled to the general circulation model ECHAM4 to simulate the chemical composition, number concentration, and size distribution of the global submicrometer aerosol. The present publication describes the new model system ECHAM4/MADE and presents model results in comparison with observations. The new model is able to simulate the full life cycle of particulate matter and various gaseous particle precursors including emissions of primary particles and trace gases, advection, convection, diffusion, coagulation, condensation, nucleation of sulfuric acid vapor, aerosol chemistry, cloud processing, and size-dependent dry and wet deposition. Aerosol components considered are sulfate (SO 4 ), ammonium (NH 4 ), nitrate (NO 3 ), black carbon (BC), particulate organic matter (POM), sea salt, mineral dust, and aerosol liquid water. The model is numerically efficient enough to allow long term simulations, which is an essential requirement for application in general circulation models. Since the current study is focusing on the submicrometer aerosol, a coarse mode is not being simulated. The model is run in a passive mode, i.e. no feedbacks between the MADE aerosols and clouds or radiation are considered yet. This allows the investigation of the effect of aerosol dynamics, not interfered by feedbacks of the altered aerosols on clouds, radiation, and on the model dynamics.In order to evaluate the results obtained with this new model system, calculated mass concentrations, particle number concentrations, and size distributions are compared to observations. The intercomparison shows, that ECHAM4/MADE is able to reproduce the major features of the geographical patterns, seasonal cycle, and vertical distributions of the basic aerosol parameters. In particular, the model performs well under polluted continental conditions in the northern hemispheric lower and middle troposphere.Correspondence to: A. Lauer (axel.lauer@dlr.de) However, in comparatively clean remote areas, e.g. in the upper troposphere or in the southern hemispheric marine boundary layer, the current model version tends to underestimate particle number concentrations.

Impact of the modal aerosol scheme GLOMAP-mode on aerosol forcing in the Hadley Centre Global Environmental Model

“…However, the need to keep track of aerosol mass and composition in each size bin makes such schemes costly to run in a large-scale general circulation model. Two-moment modal schemes have been developed as a compromise: they also simulate both aerosol mass and number, but the aerosol size distribution is represented by a superposition of modes, typically assumed lognormal (Ghan et al, 2001;Easter et al, 2004;Stier et al, 2005;Liu et al, 2005;Lauer et al, 2005;Bauer et al, 2008;Pringle et al, 2010;Liu et al, 2012). The M7 scheme (Vignati et al, 2004) and the Global Model of Aerosol Processes modal scheme, GLOMAP-mode , define 7 modes, representing a nucleation mode, and soluble and insoluble modes for each of the Aitken, accumulation and coarse size ranges.…”

Emulation of a complex global aerosol model to quantify sensitivity to uncertain parameters

“…Until recently, climate models used simple representations of aerosol, which were based mostly on just particle mass. But the recognition that simplification of physical processes limits model predictive capability has led to the development of more complex "second generation" aerosol microphysics schemes that are intended to enhance model realism and improve the reliability of predictions (Binkowski and Shankar, 1995;Jacobson, 1997;Whitby and McMurry, 1997;Ackermann et al, 1998;Ghan et al, 2001;Adams and Seinfeld, 2002;Lauer et al, 2005;Liu et al, 2005;Stier et al, 2005;Spracklen et al, 2005a;Debry et al, 2007;Spracklen et al, 2008). Model realism has undoubtedly improved, but the diversity in model aerosol radiative forcing estimates has remained high in successive IPCC assessments (Schimel et al, 1996;Penner et al, 2001;Forster et al, 2007).…”

ESMValTool (v1.0) – a community diagnostic and performance metrics tool for routine evaluation of Earth system models in CMIP

“…23 for the CMIP5 models in comparison to MODIS and ESACCI-AEROSOL. Finally, more specific aerosol diagnostics have been implemented to compare aerosol vertical profiles of mass and number concentrations and aerosol size distributions, based on the evaluation work by Lauer et al (2005) and Aquila et al (2011). These diagnostics, however, use model quantities that were not part of the CMIP5 data request and therefore will not be discussed here.…”