Abstract
Abstract. The climate-chemistry-aerosol-cloud-radiation feedbacks are important processes occurring in the atmosphere. Accurately simulating those feedbacks requires fully-coupled meteorology, climate, and chemistry models and presents significant challenges in terms of both scientific understanding and computational demand. This paper reviews the history and current status of the development and application of online-coupled meteorology and chemistry models, with a focus on five representative models developed in the US including GATOR-GCMOM, WRF/Chem, CAM3, MIRAGE, and Caltech unified GCM. These models represent the current status and/or the state-of-the science treatments of online-coupled models worldwide. Their major model features, typical applications, and physical/chemical treatments are compared with a focus on model treatments of aerosol and cloud microphysics and aerosol-cloud interactions. Aerosol feedbacks to planetary boundary layer meteorology and aerosol indirect effects are illustrated with case studies for some of these models. Future research needs for model development, improvement, application, as well as major challenges for online-coupled models are discussed.
Highlights
The climate-chemistry-aerosol-cloud-radiation feedbacks are important in the context of many areas including climate modeling, air quality/atmospheric chemistry modeling, numerical weather and air quality forecasting, as well as integrated atmospheric-ocean-land surface modeling at all scales
Aerosol feedbacks are traditionally neglected in meteorology and air quality modeling due largely to historical separation of meteorology, climate, and air quality communities as well as our limited understanding of underlying mechanisms
CAM3 simulates the emissions of soil dust and sea-salt (Tie et al, 2005; Mahowald et al, 2006 a, b) as well as biogenic species online based on the Model of Emissions of Gases and Aerosols from Nature (MEGAN) of Guenther et al (2006) that has been incorporated into CAM3 along with the Model for Ozone and Related Chemical Tracers version 4 (MOZART-4) (Lamarque et al, 2005; Heald, 2007), offline biogenic emissions can be used in some CAM3 simulations
Summary
The climate-chemistry-aerosol-cloud-radiation feedbacks are important in the context of many areas including climate modeling, air quality/atmospheric chemistry modeling, numerical weather and air quality forecasting, as well. The coupling in most global online-coupled climatechemistry models, is largely incomplete; and has been done only for very limited prognostic gaseous species such as O3 and/or bulk sulfate aerosol or selected processes such as transport and gas-phase chemistry (i.e., slightlyor moderately-coupling, e.g., Hunt, 1969; Atwater, 1975; Schlesinger and Mintz, 1979; Taylor and Penner, 1994) This is mainly because such a coupling typically restricts to gas-phase or parameterized chemistry (and heterogeneous chemistry in some cases) and simple aerosol/cloud chemistry and microphysics and often neglects the feedbacks between prognostic chemical species (e.g., O3 and aerosols) and radiation (e.g., Roelofs and Lelieveld, 1995; Eckman et al, 1996; Barth et al, 2000; Wong et al, 2004; Lamarque et al, 2005) and between aerosols and clouds (e.g., Liao et al, 2003; Lamarque et al, 2005). The feedbacks between meteorology and chemical species are often neglected in many local-toregional scale online models (e.g., Uno et al, 2001, 2003), and a full range of climate-chemistry-aerosol-cloud-radiation feedbacks is treated in very few mesoscale models (e.g., Jacobson, 1994, 1997a, b; Grell et al, 2005)
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