Georgia Institute of Technology

An Adaptive Grid Version of CMAQ for

Improving the Resolution of Plumes

Fernando Garcia-Menendez Yongtao Hu

M. Talat Odman

8th Annual CMAS Conference20 October, 2008

Georgia Institute of Technology

Background

• Adaptive Grid Algorithm (1997-2001)– Srivastava, R. K., D. S. McRae, and M. T. Odman (2000) : An

adaptive grid algorithm for air quality modeling, J. Comput. Phys., 165, 437-472.

• Adaptive Grid Air Quality Model (2001-2004)• Variable Time Step Algorithm (2004-2007)

• and now …

∆t1 < ∆t2

∆t1 > ∆t2

t = N∆t2

∆t1 < ∆t2

∆t1 > ∆t2

t = N∆t2

Georgia Institute of Technology

Adaptive Grid CMAQ

• AG-CMAQ is a sophisticated piece of code that was built on top of CMAQ Version 4.5 by remaining faithful to the “Models-3” concept

• It has been verified• It can be applied through the existing framework

– No additional input files are necessary

• To use AG-CMAQ in your applications, adjust the driving force of grid adaptations by either:– Supplying a separate emissions input file for sources to be

resolved– Or changing the adaptation weight function to focus on

different pollutants, terrain, or other features.– We can show you how!

independently dependently

Georgia Institute of Technology

Code Verification• Expectation: When AG-CMAQ is not adapting it should

produce the same results as the standard CMAQ• Outcome: The results are practically the same with

very small and random differences, except for biogenic organic and nitrate aerosols where the differences are still small ( < 0.1 g m-3) but have a pattern. The source is coming from the aerosol module.Difference in Biogenic SOA Difference in Nitrate

Georgia Institute of Technology

CMAQ1.33 km grid

AG-CMAQ~ 100 m grid

Rx Burn at Ft. Benning: PM2.5

Georgia Institute of Technology

CMAQ Bug Alert!

• Several deeply hidden bugs were found in CMAQ– Instability in advection due to improper time step

• CFL stability condition is violated if the max. wind speed decreases by more than 1/3 during the output time step

– Incomplete advection due to time step not dividing MINSYNC wholly.

– Incomplete horizontal diffusion due to misplaced update of concentration array

– Smagorinsky formulation in HDIFF assumes Cartesian coordinates (watch out Hemispheric Applications!)

• Details and fixes are in my website– http://people.ce.gatech.edu/~todman/

Georgia Institute of Technology

Problem with WRF!1.3 km grid resolution UWIND is oscillating

Atlanta Smoke Event (CMAQ)

Atlanta Smoke Event (AG-CMAQ)

Georgia Institute of Technology

Atlanta Smoke Event (28 Feb. 2007) Jefferson St.

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Georgia Institute of Technology

Adaptor

CMAQ

Daysmoke

MM5 (WRF)

ChemicalCoupling Ambient concentrationsParcel/Puff/Plume concentrations

Grid

Grid

Grid

Parcels

GridSupport?

Distributions

Parcels mixed in grid cells

Meteorology

MeteorologyParticles/CCN

Handover

d = downwind distance

Emissions

ConcentrationsMeteorology

Smoke Impact Simulation System

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Daysmoke

Poster• A sub-grid scale model for the treatment of biomass

burning plumes in CMAQ by Aika Yano et al.

Georgia Institute of Technology

Acknowledgements

• Strategic Environmental Research and Development Program (SERDP)

• Joint Fire Science Program (JFSP)

• U.S. Forest Service– Dr. Gary L. Achtemeier