GEOS-CHEM Modeling for Boundary Conditions and

Natural Background

James W. BoylanGeorgia Department of Natural Resources

- VISTAS

National RPO Modeling MeetingDenver, CO

May 25, 2004

Outline

• Objectives and Background• Summary of Modeling Results• Update on RPO GEOS-CHEM

Project• Natural Background Options• Group Discussion

Objectives• Run the GEOS-CHEM global chemical

transport model for CY2002 to develop temporally and spatially varying boundary conditions (BCs) for the 36-km national modeling grid to be used for ozone, PM2.5, and regional haze modeling.

• Run GEOS-CHEM to evaluate natural background visibility and transboundary pollutant transport.

GEOS-CHEM Global Chemical Transport Model

• Driven by Goddard Earth Observing System (GEOS) assimilated meteorological data from the NASA Data Assimilation Office (DAO)

• Horizontal resolution 1o x 1o to 4o x 5o (user-selected), 48 levels in vertical (80 km)

• Ozone-NOx-VOC (“oxidant”) chemistry: ~80 species, 400 reactions

• Aerosols: H2SO4-HNO3-NH3, organic carbon (OC), elemental carbon (EC), soil dust (four size classes), sea salt (two size classes)

• Oxidant and aerosol simulations coupled by photolysis frequencies, heterogeneous chemistry, sulfate/nitrate formation, HNO3(g)/NO3

- partitioning • Multi-process wet deposition scheme• http://www-as.harvard.edu/chemistry/trop/geos

3-Hourly GEOS-CHEM Sulfate BCs

EPADefault

SO

4

m

icro

gra

m/m

3

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Western BCSouthern BC Northern BC

June July August

SO4 Seasonal Boundary Condition Time Series Summer

((July July monthly avg., 2001)monthly avg., 2001)

PM diff. (GCM BCs/ICs – Default BCs/ICs)

PM 2.5 PM Sulfate

Slide provided by: Carey Jang, U.S. EPA

PM diff. (GCM BCs/ICs – Default BCs/ICs)

PM 2.5 PM Sulfate

((July July 22, 2001, daily average)22, 2001, daily average)Slide provided by: Carey Jang, U.S. EPA

((January January monthly avg., 2001)monthly avg., 2001)

PM diff. (GCM BCs/ICs – Default BCs/ICs)

PM 2.5 PM Nitrate

Slide provided by: Carey Jang, U.S. EPA

PM diff. (GCM BCs/ICs – Default BCs/ICs)

PM 2.5 PM Nitrate

((Jan. Jan. 13, 2001, daily average)13, 2001, daily average)Slide provided by: Carey Jang, U.S. EPA

January 2002 EpisodeGEOS-CHEM (S) vs. EPA-Default

CASTNET TNO3 (VISTAS) CASTNET TNO3 (US)

Summary of Results• Summer Episodes

– Significant change in ozone in WRAP, MRPO, and MANE-VU

– Significant change in PM2.5 (sulfate) in WRAP

• Winter Episodes– Significant change in PM2.5 (nitrate) in MRPO,

MANE-VU, and VISTAS – related to ozone or reactive nitrogen BCs (?)

– Ozone performance worse (low bias) – BC low in north

– NO2, NO3, and TNO3 performance better

• Mexican Fires– Significant change in PM2.5 (OC & EC) in

CENRAP, WRAP, VISTAS, and MANE-VU

GEOSCHEM ; DAO

Comparison of Wind FieldsComparison of Wind Fields

GEOSCHEN : Westerly (inflow)

MM5 : Northerly (outflow)

GEOSCHEM : Easterly and northerlyMM5 : Clock wise rotation motion

• Possible inconsistencies between the global and regional scale dynamics• MM5 Outflow and GEOS-CHEM Inflow OK• GEOS-CHEM Outflow and MM5 Inflow

Problems• Remedy (being tested by UH)

• Run regional scale model with global scale output as input for initialization and analysis nudging

• Too late to use this remedy for VISTAS modeling

• Other Options?• In the case where GEOS-CHEM outflow and

MM5 inflow, could replace hourly BC with seasonal average BC or seasonal average inflow BC

Linking GEOS-CHEM and CMAQ

GEOS-CHEM Modeling for RPOs

• Daniel Jacob (Harvard) will be performing annual (CY2002) GEOS-CHEM modeling for the RPOs

• Project is being managed by a steering committee comprised of representatives from all 5 RPOs– VISTAS volunteered to take the lead

• Workplan identifies three major tasks to be completed by August 31, 2004

• VISTAS is funding Daewon Byun (UH) to convert GEOS-CHEM outputs to boundary conditions for CMAQ (CAMx?)

Harvard Deliverables• Global Emissions Inventory for CY2002

– Biomass burning inventory with 1°x1° resolution

• GEOS-CHEM global 3-D concentration fields (4°x 5° grid) with 3-hour resolution for three full-year simulations– Baseline 2002 simulation with all anthropogenic

emissions– Sensitivity simulation with U.S. anthropogenic

emissions turned off– Sensitivity simulation with worldwide anthropogenic

emissions turned off

• Model Performance Evaluation (MPE) – IMPROVE and CASTNET– Monthly mean SO4, NO3, TNO3, NH4, OC, EC, and

dust– Extensive MPE conducted under EPRI funding

Natural Background Runs

• The GEOS-CHEM model results can be used to evaluate natural conditions at Class I areas

• “Directly Method”: Turn off U.S. anthropogenic emissions in GEOS-CHEM and examine pollutant concentrations at Class I areas– 4°x5° resolution too coarse to be useful

(especially for mountainous and costal sites)– 1°x1° resolution will be more useful than 4°x 5°

resolution, but still might not meet our needs• Results available through EPRI funding in Fall 2004

4°x 5° GEOS-CHEM Grid

Natural Background Runs• “Indirect Method”: Turn off U.S.

anthropogenic emissions in GEOS-CHEM to generate a new set of BCs that will be used for a CMAQ run at 36/12 km resolution with U.S. anthropogenic emissions turned-off.– New boundary conditions must be generated with

GEOS-CHEM (no U.S. emissions) to eliminate recirculated U.S. anthropogenic emissions from the boundary conditions

– Advantages: finer grid resolution, better meteorological fields, more advanced air quality model

– Disadvantages: time and $$$

• Same concepts for evaluating “true” natural conditions by removing worldwide anthropogenic emissions in GEOS-CHEM.

4°x 5° GEOS-CHEM Grid

4°x 5° GEOS-CHEM Grid

Discussion Issues• Options for addressing inconsistencies

between the global and regional meteorological fields?

• Natural Background Simulations– Direct or Indirect Method?– Turn-off U.S. anthropogenic emissions or

turn-off all North American anthropogenic emissions?

• Boundary Conditions for 2002 “typical” and 2018 “typical” CMAQ simulation– Use 3-hour GEOS-CHEM BCs or use seasonal

average GEOS-CHEM BCs or use seasonal average inflow/outflow BCs?

• Other Issues?