Sections

Chemistry Modeling

Section Head: Jean-Francois Lamarque

ACOM builds, critically evaluates and applies process, regional- and global-scale models that address atmospheric chemistry research questions, with a focus on couplings between different components of the Earth system (water cycle, biosphere, cryosphere). This section provides the necessary modeling tools to address the following scientific challenges

    • Air Quality Prediction Research  

Poor air quality (AQ) is the source of significant human premature mortality and ecosystem damage, and thus is an issue of major societal concern on a global scale.  In the United States alone, early mortalities due to exposure to air pollutants (mostly particulate matter, PM) are thought to exceed 100,000 per year, with health care costs exceeding $10 billion per year for related morbidities, while crop damage (primarily due to ozone exposure) is estimated to exceed $1 billion per year.  Although it is evident that air quality in major U.S. cities has improved dramatically over the last few decades, exceedances of ozone and PM standards are still commonplace.  AQ problems are even more severe in the developing world, due to increasing populations, trends toward urbanization, and generally lagging technological capacity and emission-control standards. Of particular concern is that air pollution is one of the fastest growing health risks in the world, with a 300% increase in premature deaths from 1990 to 2010. The quantification and prediction of air quality (and more generally, atmospheric composition) is thus of critical societal importance.  This must include an understanding not only of AQ-related issues in urban areas, but also an understanding of the impacts of urban emissions on regional to inter-continental scales.   ACOM will continue its studies of air quality and atmospheric composition, using an integrated approach that includes laboratory-based process studies, in situ and remote observations, modeling and data assimilation.  The goal of the research is to increase predictive capability for present and future AQ, and thus provide a strong scientific foundation upon which mitigation and adaptation strategies and policy decisions can be based.  A particular target is the development of a high resolution coupled AQ – meteorological forecasting capability. 

    • Interactions between Chemistry and the Climate/Weather System

Earth’s climate is changing as the result of human activity.  While increased levels of atmospheric CO2 are the major forcing agent, climate is also impacted by changes in other trace species, including methane, nitrous oxide, halocarbons, tropospheric and stratospheric ozone, and aerosols, whose lifetimes and distributions (and thus climatic impacts) are all controlled by chemistry.  Although present-day aerosols probably act to cool the atmosphere on the global scale, there is considerable uncertainty regarding their overall climatic impact (including the warming effects of black carbon).  Roughly half of this aerosol loading is believed to be formed from organic species, yet the chemistry and physics that lead to their production, growth and loss is poorly understood, as are their optical and hygroscopic properties.  The biosphere acts as a major source of atmospheric trace gases, particularly reactive volatile organic compounds (VOCs), and the nature and strength of these emissions are evolving as the result of climate and land-use change. The composition of the stratosphere is also changing as the result of human activity – levels of greenhouse gases continue to increase, while stratospheric ozone recovers following the Montreal Protocol - and these changes influence climate in the lower atmosphere.

Research Groups

The Global Chemistry Modeling section currently focuses on the development and applications of the following models

    • CAM-Chem: Community Atmosphere Model with Chemistry
    • WACCM: Whole Atmosphere Community Climate Model


Both models are integral parts of the Community Earth System Model (www.cesm.ucar.edu) and are developed under the general direction of the CESM Chemistry-Climate Working Group and Whole Atmosphere Working Group. These models are extensions to the chemistry-transport models MOZART.  MOZART-4, while still available for download, is not being supported for further development.

The Regional & Process Modeling section currently focuses on the development and applications of the following models

    • BOXMOX: Box Model
    • DICE-Africa: Diffuse and Inefficient Combustion Emissions in Africa
    • FINN: Fire INventory from NCAR
    • GECKO-A: Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere
    • NCARMM: the NCAR Master Mechanism chemistry box model
    • TUV: Tropospheric Ultraviolet and Visible radiation model
    • WRF-CHEM: Weather and Research Forecasting model with Chemistry

 

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ACOM | Atmospheric Chemistry Observations & Modeling