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

[摘要] The aerosol dynamics module MADE has been coupled to the generalcirculation model ECHAM4 to simulate the chemical composition,number concentration, and size distribution of the global submicrometeraerosol. The present publication describes the new model systemECHAM4/MADE and presents model results in comparison withobservations. The new model is able to simulate the full life cycle ofparticulate matter and various gaseous particle precursors includingemissions 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 wetdeposition. Aerosol components considered are sulfate (SO₄),ammonium (NH₄), nitrate (NO₃), black carbon (BC),particulate organic matter (POM), sea salt, mineral dust, and aerosolliquid water.The model is numerically efficient enough to allow longterm simulations, which is an essential requirement for application ingeneral circulation models.Since the current study is focusing on the submicrometer aerosol, acoarse mode is not being simulated. The model is run in apassive mode, i.e. no feedbacks between the MADE aerosols and cloudsor radiation are considered yet. This allows the investigation of theeffect of aerosol dynamics, not interfered by feedbacks of the alteredaerosols 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, andsize distributions are compared to observations.The intercomparison shows, that ECHAM4/MADE is able to reproduce the majorfeatures of the geographical patterns, seasonal cycle, and verticaldistributions of the basic aerosol parameters. In particular, themodel performs well under polluted continental conditions in thenorthern hemispheric lower and middle troposphere. However, incomparatively clean remote areas, e.g. in the upper troposphere or inthe southern hemispheric marine boundary layer, the current modelversion tends to underestimate particle number concentrations.

[学科分类] 大气科学