OUTLINE
• Why are we interested in linking GEOSCHEM with regional air quality model
(CMAQ)?
• Technical issues to consider when linking
GEOS-CHEM & CMAQ
• Upcoming results from two relevant EPA
projects
Why does EPA want to link GEOS-CHEM with
regional air quality model (CMAQ)?
– Intercontinental transport of pollutants
 What are the impacts of trans-Pacific transport of O3, PM, and
other pollutants on U.S. air quality?
 How about trans-Atlantic transport (export)?
– Climate and Air Quality studies
 Climate change impacts on air quality
 Air quality impacts on climate
– Continental domain CMAQ simulations
 Can model results improve using the boundary conditions
provided by the GEOS-CHEM?
U.S. CMAQ Modeling: O3
(e.g., 1996 July Max in ppb)
149
56
99
62
134
76
137
107
215
132
139
126
131
127
144
113
194
119
USEPA Community Multiscale Air
Quality Model (CMAQ)
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Gas phase chemical mechanisms:
SAPRC99, CB4, RADM2
Aerosols: Binkowski and Roselle [JGR, 2003]
Resolution ranges from regional (e.g., 36 km2 grid) to
urban (e.g., 4 km2 grid) scale
Vertical layers range (e.g., 15 to 23) and go up to
100mb
Emission fields based on USEPA National Emissions
Inventory (e.g., NEI99 v2), BEIS 3.10, and Mobile 6
Meteorology typically generated using the NCAR/Penn
State Mesoscale Model (MM5 v3)
GEOS-CHEM
SAPRC-99
CB4
Ox
NOx
HNO3
N2O5
HNO4
CO
H2O2
CH2O
SO2
PAN
PMN
PPN
Ox (O3+NO2)
NOx (NO+NO2)
Nitric Acid
N2O5
Peroxynitric Acid
CO
Hydrogen Peroxide
Formaldehyde
SO2
PAN
MPAN
PPN
O3, NO2
NO, NO2
HNO3
N2O5
HNO4
CO
H2O2
HCHO
SO2
PAN
MA_PAN
PAN2
O3, NO2
NO, NO2
HNO3
N2O5
PNA
CO
H2O2
FORM
SO2
PAN
PAN
PAN
C2H6
ALK4
C3H8
PRPE
ACET
MEK
ALD2
RCHO
ISOP
MVK
MACR
MP
R4N2
Ethane
Alkanes(>=C4)
Propane
Propene
Acetone
Ketones(>C3)
Acetaldehyde
Aldehyde(>C3)
Isoprene
Methylvinylketone
Methacrolein
Methyl Hydroperoxide
Alkylnitrate(>C3)
ALK1
ALK3+ALK4+ALK5
ALK2
OLE1
ACET
MEK
CCHO
RCHO
ISOPRENE
MVK
METHACRO
COOH
RNO3
0.4*PAR
4*PAR
3*PAR
(1*OLE)+ (1*PAR)
3*PAR
4*PAR
ALD2
ALD2
ISOPRENE
ISPD (products of isoprene rxns)
ISPD (products of isoprene rxns)
UMHP
2*NTR
SO4
NH3
NH4
NO3 (p)
Sulfate
Ammonia
Ammonium
Particulate Nitrate
ASO4I+ASO4J
NH3
ANH4I+ANH4J
ANO3I+ANO3J
ASO4I+ASO4J
NH3
ANH4I+ANH4J
ANO3I+ANO3J
DMS
MSA
Dimethyl Sulfate
Methyl Sulfionic Acid
Spatial Resolution Issues
• Scale of CMAQ simulations
– regional (e.g., 36×36 km2) scale
– nested finer scale (e.g., 12×12 km2, 4×4 km2)
– Hourly time scale for input and output
• Matching GEOS-CHEM fields with CMAQ for
boundary conditions
– If 4×5, > 10 CMAQ grids to 1 GEOS-CHEM grid
along vertical boundaries
– Different projections (cartesian vs conformal)
CMAQ upper boundary conditions
• CMAQ typically up to 100 mb
• With fairly coarse layers at top, tropopause not
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resolved
Without tropopause dynamics, lower
stratospheric [O3 ] not an option
O3 fluxes from GEOS-CHEM would be an option
Consistencies between GEOS-CHEM and
CMAQ
• Emission inventories over U.S.
• Global Climate Modeling for future climate
change scenarios
– MM5 mesoscale model can use GCM BCs
– Similar greenhouse gas scenarios
• Chemical fields simulations
– O3
– Speciated aerosols (sulfate, nitrate, organics,…)
– Hg
Upcoming results from 2 relevant
EPA studies
• Climate Impacts on Regional Air Quality
(CIRAQ): USEPA ORD
• Intercontinental transport and Climate Effects
of Air Pollution (ICAP): USEPA OAQPS
Simulations from CIRAQ Project
(Climate Impacts on Regional Air Quality)
For U.S. Continental Domain
10-yr MM5 mesoscale model runs (complete 2004)
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– 1990-2003
– 2040-2050
• 36×36 km2 resolution
• GISS II’ GCM boundary conditions (collaboration with Harvard)
• IPCC A1B greenhouse gas emission scenario
5-yr CMAQ simulations (complete 2006)
– 1999-2003
– 2045-2050
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O3 and PM predictions
36×36 km2 resolution
Base NEI99 v2 emissions for 1st incremental phase tests
SAPRC chemical mechanism
Boundary conditions driven by GEOS-CHEM (with GISS II’ GCM, IPCC A1B)
(collaboration with CMU and Harvard, through STAR EPA coops)
Analysis of results included in EPA GCRP air quality national
assessment report in 2007
Simulations from CIRAQ Project
(Climate Impacts on Regional Air Quality)
• Future (2050) air quality emission scenarios
– Technology assessments for mobile and utility sectors
– Population and economic projections consistent with IPCC, more
spatially resolved
– External collaborations to be determined
– Proposals under review at STAR program
• CMAQ 2050 simulations with future air quality
emission scenarios (tentatively planned for 2010 EPA
GCRP AQ assessment)
Results from ICAP Project
(Intercontinental transport and Climate Effects of Air Pollution)
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2001 trans-Pacific and trans-Atlantic domain
CMAQ simulations, 108-km grid (spring
2004)
2001 national domain CMAQ simulations,
36-km grid; episodic eastern & western US
domains, 12-km grid (spring/summer 2004)
Emission inventory for Asia (O3, PM, Hg)
ICAP Trans-Pacific Domain
ICAP Trans-Atlantic Domain
ICAP: Refinement of Asian emission inventory
for CMAQ Trans-Pacific Simulations
NO emissions
Air Quality Modeling over China : PM 2.5
Next Directions at EPA
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Assessment of future climate change impacts on
AQ expanded to 2100
Develop bidirectional feedback between CMAQ
and MM5/WRF for aerosol impacts on
meteorology
Agency long-term planning for intercontinental
transport research underway