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ON AERODYNAMIC AND BOUNDARY LAYER RESISTANCES WITHIN DRY DEPOSITION MODELS
Citation:
Brashers, B., Y. Wu, J E. Pleim, AND P L. Finkelstein. ON AERODYNAMIC AND BOUNDARY LAYER RESISTANCES WITHIN DRY DEPOSITION MODELS. Presented at American Geophysical Union Fall Meeting, San Francisco, CA, December 13-17, 1999.
Impact/Purpose:
This task has the following objectives:
Improve modelers' ability to focus on scientific and policy issues in modeling studies by providing software that supports composing, applying, and evaluating complex systems of models.
Improve the understanding of the interaction of the atmosphere and the underlying surface, especially the flux of mass in both directions, and EPA's ability to simulate that interaction.
Contribute to multimedia studies and assessments by applying state-of-the-art atmospheric models, estimating atmospheric contributions to multimedia issues and the sources of those contributions, and evaluating the models' strengths and weaknesses.
Description:
There have been many empirical parameterizations for the aerodynamic and boundary layer resistances proposed in the literature, e.g. those of the Meyers Multi-Layer Deposition Model (MLM) used with the nation-wide dry deposition network. Many include arbitrary constants or parameters that are difficult to determine a priori, such as a typical leaf diameter. These become, in effect, tunable parameters. Although they can be used to minimize the difference between observations and models for specific sites, they can vary from site to site and add to the difficulty in working with large-scale projects. Some of the popular parameterizations of the aerodynamic resistance employ drastic restrictions, or are discontinuous functions of their inputs. Many take into account only shear-driven turbulence, ignoring the effects of buoyancy and stratification. We present a simple closed-form parameterization for the aerodynamic resistance based on theoretical arguments. Monin-Obukhov (MO) similarity theory and the associated Businger-Dyer stratification corrections are used to estimate the aerodynamic resistance. Differences in functional form between the MO and resistance frameworks are discussed. A short review of boundary layer resistance parameterizations is presented, and a theoretically-based form is chosen. Differences between eddy correlation measurements over various crops and forests and the MLM, with both the standard and new resistances, are presented.