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.