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A MULTILAYER BIOCHEMICAL DRY DEPOSITION MODEL 1. MODEL FORMULATION
Citation:
WU, Y., B. BRASHERS, P. L. FINKELSTEIN, AND J. E. PLEIM. A MULTILAYER BIOCHEMICAL DRY DEPOSITION MODEL 1. MODEL FORMULATION. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, 108(D1):ACH1-1-ACH1-12, (2003).
Impact/Purpose:
The objectives of this task are to continue development and improvement of EPA's mesoscale (regional through urban scale) air quality modeling systems, such as the Community Multiscale Air Quality (CMAQ) model, as air quality management and NAAQS implementation tools. This task focuses on needed research and development of air quality models targeted for a major CMAQ model release in FY08. Model development for a broad scope of application is envisioned. For example, CMAQ will need to be able to simulate air quality feedbacks to meteorology and climate as well as intercontinental transport. The 2008 release of CMAQ is timed to coincide with EPA/OAR's and the states' needs for an improved model for assessments of progress (mid-course corrections) in the post-SIP submittal timeframe.
Description:
A multilayer biochemical dry deposition model has been developed based on the NOAA Multilayer Model (MLM) to study gaseous exchanges between the soil, plants, and the atmosphere. Most of the parameterizations and submodels have been updated or replaced. The numerical integration was improved, and an aerodynamic resistance based on Monin-Obukhov theory was added. An appropriate parameterization for the leaf boundary layer resistance was chosen. A biochemical stomatal resistance model was chosen based on comparisons of four different existing stomatal resistance schemes. It describes photosynthesis and respiration and their coupling with stomatal resistance for sunlit and shaded leaves separately. Various aspects of the photosynthetic process in both C3 and C4 plants are considered in the model. To drive the photosynthesis model, the canopy radiation scheme has been updated. Leaf area index measurements are adjusted to account for stem area index. A normalized soil water stress factor was applied to potential photosynthesis to account for plant response to both drought and water-logging stresses. A new cuticle resistance model was derived based on membrane passive transport theory and Fick's first law. It accounts for the effects of diffusivity and solubility of specific gases in the cuticle membrane, as well as the thickness of the cuticle membrane. The model is designed for use in the nationwide dry deposition networks, for example, the Clean Air Status And Trends Network (CASTNet), and mesoscale models, for example, the Community Multiscale Air Quality model (CMAQ) and even the Weather Research and Forecasting model (WRF).