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JEHN-YIH JUANG , Donna Schwede, and Jon Pleim Atmospheric Sciences Modeling Division, U.S. EPA-NOAA Research Triangle Park, NC 2007 Annual CMAS Conference, Chapel Hill, NC October 1 st -3 rd ,2007. Utilizing the Mosaic Approach to Estimate Deposition Velocities in the CMAQ Model. - PowerPoint PPT Presentation
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JEHN-YIH JUANG, Donna Schwede, and Jon Pleim
Atmospheric Sciences Modeling Division, U.S. EPA-NOAAResearch Triangle Park, NC
2007 Annual CMAS Conference, Chapel Hill, NC
October 1st -3rd ,2007
Utilizing the Mosaic Approach to Estimate Deposition
Velocities in the CMAQ Model
Introduction
• In the current CMAQ model
Deposition velocity (Vd) is estimated from the grid-scale parameters
The impact of the sub-grid scale land use is not well explored
Grid scale
Vd
Introduction-Cont.
• In the proposed Mosaic approach
Characterize and quantify the contributions of the sub-grid scale
land use to the Vd and fluxes within grid cell
Improve the usefulness of CMAQ output in ecological assessments
Facilitate future process-based simulation of bi-directional chemical
exchange across water, soil and vegetation surfaces
Vd
Vdj
Sub-grid scale
• Estimate of Vd
• For a given chemical
• Assume PAR, Ta, and RHs = constant in
each grid cell
• Vd is influenced by sub-grid land use (LU)
and soil type. However, the soil type is not easy to separat from the LU
Deposition Velocity
Mosaic Approach
• Apply the sub-grid scale parameters to estimate Vd
• Utilize USGS Land Use Classification
• Estimate u* and zoj base on the assumptions of (1) Uu*= Uju*j (Walcek,
1986) and (2) logarithmic wind profile
• Estimate LAIj from the meteorological model.
USGS Land Use Classification
Land Use Characteristics
Roughness Length and Friction Velocity
• UTC 20:00, July 27, 2001
Vd Comparison
• UTC 20:00, July 27, 2001
Vd Comparison-Cont.
• 10-day simulation: July 22~July 31, 2001
Impact of the Land Use Compositions on Vd
Mixed Forest
Decids. Broadlf.Water Body
Crop/Wood
Evergrn Needlf.
Drylnd Crop. Past.
Summary (1)
• Conclusions
The proposed mosaic approach can sufficiently estimate the
contribution of sub-grid scale land use on the deposition velocity.
In this case study, the deposition velocity of ozone derived from the
mosaic approach departs roughly by 15% at most from the original
MCIP model.
The coverage of the water body in each grid cell strongly impacts the
estimation of the mosaic approach.
Summary (2)
• Future Work
Integrate the information of the sub-grid soil types and the sub-grid
land use composition.
Seasonality analysis
Investigate the impact on the bi-directional fluxes.
Acknowledgements & Disclaimer
• The authors would like to thank the discussion and the input from Ellen Cooter, Jesse
Bash, and Tanya Otte.
• This research was supported in part by an appointment to the Research Participation
Program at the National Exposure Research Laboratory administered by the Oak Ridge
Institute for Science and Education through an interagency agreement between the U.S.
Department of Energy and the U.S. Environmental Protection Agency.
• Disclaimer: The research presented here was performed under the Memorandum of
Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S.
Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA)
and under agreement number DW13921548. This work constitutes a contribution to the
NOAA Air Quality and Global Climate Programs. Although it has been reviewed by EPA
and NOAA and approved for publication, it does not necessarily reflect their policies or
views.