Utilizing the Mosaic Approach to Estimate Deposition Velocities in the CMAQ Model

1. 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 1st -3rd ,2007 Utilizing the Mosaic Approach to Estimate Deposition Velocities in the CMAQ Model

2. 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 Vd Grid scale

3. 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

4. Deposition Velocity • 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

5. 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.

6. USGS Land Use Classification

7. Land Use Characteristics

8. Roughness Length and Friction Velocity UTC 20:00, July 27, 2001

9. Vd Comparison • UTC 20:00, July 27, 2001

10. Vd Comparison-Cont. • 10-day simulation: July 22~July 31, 2001

11. Impact of the Land Use Compositions on Vd Mixed Forest Decids. Broadlf. Water Body Crop/Wood Drylnd Crop. Past. Evergrn Needlf.

12. 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.

13. 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.

14. 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.