Post on 29-Jan-2016
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?