Shawn J. RoselleNOAA Atmospheric Science Modeling Division

In partnership with the U.S. Environmental Protection Agency

Research Triangle Park, NC

CMAQ Model Development: Current Model Configuration

and Future Plans

ACCENT-CMAS Training Workshop on Air Quality Modeling, Sofia, BulgariaAugust 6, 2006

Summary

• Background on modeling

• Current model features

• New developments on the horizon

Background

Role of Models in the Air Quality Planning Process

• Air quality modeling is a major part of the United States’ implementation of the National Ambient Air Quality Standards (NAAQS) for ozone and PM2.5

• State-of-science models are needed in the State Implementation Plan (SIP) process

Models are Central to the Air Quality Planning Process (cont.)

• Multi-pollutant capabilities O3, PM, acid/nutrient deposition, regional haze, air

toxics, Hg

• Multi-scale capabilities Synthesize scale interactions between continental/

regional/ urban

• Models are the only predictive tools to estimate emissions growth/change and the impacts of potential emissions control strategies on future-year air quality

Categories of Air Quality Models• Dispersion models (traditional)

Steady-state Gaussian models

• Receptor-oriented models Diagnostic; not predictive Provide data to indicate primary source

categories affecting a receptor

• Source-oriented models Predictive, as well as diagnostic Lagrangian or Eulerian frames of reference

grid cell

CMAQ Modeling System

SMOKE

Anthro and Biogenic Emissions processing

Fifth Generation Mesoscale Model (MM5)

or

Weather Research and Forecast Model (WRF)

CMAQ AQ Model-

Chemical-Transport Computations

Met-Chem Interface Processor (MCIP)

Met. data prep

NOAA Weather Observations

EPA Emissions Inventory

Hourly 3-D Gridded Chemical Concentrations

grid cell

36-km MM5165 x 129 x 34

36-km CMAQ148 x 112 x 14

12-km MM5202 x 208 x 34

12-km CMAQ199 x 205 x 14

Domains for Annual Simulations

Meteorology

• Penn State/NCAR Mesoscale Model-Gen. 5 (MM5) – community meteorology model Principally used as a weather forecast

model• MM5 is widely used in air quality community

– Emphasis on processes important for air quality– Four-dimensional data assimilation (FDDA)

» Resulting fields: model+observations

• Weather Research and Forecast (WRF) is the successor model to MM5

Sample MM5 Output (36-km grids)MM5 Winds and Precipitation

12 UTC 22 July 1998120-h simulation

“Daily Weather Map” courtesy of NOAA

Meteorology (cont.)

• ASMD meteorological model research Land-surface modeling (Pleim-Xiu model) Planetary Boundary Layer (PBL) processes Linkage between meteorology/chemistry

models (MCIP) Four-dimensional data assimilation (FDDA

in MM5) NOAA’s Weather Research and Forecast

(WRF) model testing and adaptation to CMAQ model system

Emissions

• Sparse Matrix Operator Kernel Emissions (SMOKE) system Includes emissions from point, area, mobile,

and natural sources

• R&D for meteorologically-dependent emissions VOCs from vegetation and NOx from soils

(BEIS3) Sea salt via wind/wave action Wildland fires and prescribed burns Blowing dust / agricultural sources of NH3

Solves atmospheric transport-diffusion equations, with chemistry, aerosols, and other relevant processes

Time-splitting of science processes

tzyxp

i

tzyx

i

t

c

t

c

,,,,,,

Community Multiscale Air Quality (CMAQ) Model

where i = chemical speciesx,y,z = 3-D space coordinatest = timep = processes

Emissions

CloudsClouds

Chemistry, AerosolsChemistry, Aerosols

Horizontal transport and diffusion

Vertical transport and diffusion

Plume-in-grid

CMAQ Response to Emissions Changes

CMAQ Response to Emissions Changes

CMAQ Model (cont.)

• Current Research Vertical diffusion

• Boundary layer turbulence– Asymmetric Convective Model v2

Deposition• Surface fluxes; land-surface modeling• Evaluation with flux field measurements

Plume-in-Grid• Sub-grid plume descriptions

Numerical algorithms• High performance computing

• Gas-phase Chemistry Chemical kinetic mechanisms

• Carbon Bond (CB) series• Statewide Air Pollution Research Center

(SAPRC) series• Mechanism adaptation and development of

efficient numerical solvers

CMAQ Model (cont.)

CMAQ Model (cont.)

• Aerosols Modal Approach Thermodynamic gas/aerosol partitioning Nucleation, condensation, coagulation Heterogeneous chemistry Secondary organic aerosol production Inorganic aerosol chemistry

AitkenAccumulation

Coarse

H2SO4

CMAQ Model (cont.)

COARSE MODE

NO3-

NH4+

SO4=

Na+

Cl-

H2O

POA

SOAa

SOAb

EC

Other

SVOCs

HNO3

NH3

H2O

Na+, Cl-, SO42-

Soil, Other

2 FINE MODES

Aromatics

Monoterpenes

HCl

• Trimodal size distribution• Aitken (0-0.1 µm), Accumulation(0.1-2.5 µm), and Coarse

• Gas/particle interactions treated for fine modes only – ISORROPIA instantaneous equilibrium

• Fine-modes coagulate

• Coarse mode, fine EC (black) & other fine PM (brown) are inert

Binkowski and Roselle, JGR, 2002

Chemical Species

Gases Particles NO2 CO PAN NH3 ASO4I AECJ

NO FORM ROR UMHP ASO4J A25I

O3 ALD2 NTR ANH4I A25J

O OLE FACD ANH4J ACORS

NO3 ETH AACD ANO3I ASEAS

O1D TOL CRES ANO3J ASOIL

OH XYL TO2 AORGPAI NUMATKN

HO2 ISOP OPEN AORGPAJ NUMACC

N2O5 PAR CRO AORGBI NUMCOR

HNO3 C2O3 MGLY AORGBJ AH2OI

HONO XO2 ISPD AORGAI AH2OJ

H2O2 XO2N SO2 AORGAJ DCV_Mie

PNA PACD SULF AECI EXT_Mie

VOCs

PM2.5

Recent chemical additions

• Air toxics – 20 species in gas phase

– Adding more toxics, including metals, semivolatiles, other Hazardous Air Pollutants (HAPs)

• Atmospheric mercury– Modifications include new cloud/aqueous phase chemistry

and gas phase reactions– CMAQ-Hg: first public release - March 2006

acetaldehyde carbon tetrachloride

ethylene oxide propylene dichloride

acrolein chloroform formaldehyde quinoline

acrylonitrile 1,3-dichloropropene

methylene chloride tetrachloroethane

1,3-butadiene ethylene dibromide napthalene trichloroethylene

benzene ethylene dichloride perchloroethylene vinyl chloride

Two CMAQ Development Tracks

• Community version Annual public releases (via CMAS) Designed for retrospective modeling for

policy and research Multiple configurations

• Air Quality Forecasting Operational Ozone and PM forecasts Integrated with NCEP forecast systems Single optimized configuration

Synergistic DevelopmentCommunity release AQF system

Faster gas-phasechemical solver (EBI)

Aerosol model upgradesAnd efficiency improvements

Modified minimum Kz

Mass conservation scheme

Modified cloud cover and convective cloud transport

New online photolysis model(work in progress)

CB05 Chemical Mechanism

Recent CMAQ Public Releases

• September 2000: CMAQv4.0• February 2001: CMAQv4.1• June 2002: CMAQv4.2.1• May 2003: CMAQv4.2.2• September 2003: CMAQv4.3• October 2004: CMAQv4.4• September 2005: CMAQv4.5• March 2006: CMAQv4.5.1

CMAQv4.5 & v4.5.1 Highlights

• Aerosols Added sea salt (fine equilibrium; non-interactive coarse mode) Updated ISORROPIA to v1.5

• Also recomputed tabulated binary activity coefficients Updated aerosol dry deposition algorithm

• Chemistry Added CB4/chlorine chemistry and associated EBI solver Added CB4/air toxics and SAPRC99/air toxics chemistry and

associated EBI solvers Beta-version of CB05 Added degradation algorithm to the generalized solvers

• Mercury Added mercury modeling capability

Chemical Mechanisms: CMAQv4.5.1

CMAQv4.5 & v4.5.1 Highlights (continued)

• Advection New mass conservation scheme using vertical velocities

derived from mass continuity• PBL modeling

New minimum Kz based on % urban land-use• Clouds

New sub-grid cloud mixing algorithm: vertical mixing algorithm based on Asymmetric Convective Model (ACM)

Aqueous Chemistry• Discontinued aerosol species lumping--separated elemental

carbon from primary aerosol; split organic aerosols into primary, secondary biogenic, and secondary anthropogenic

• Plume-in-Grid Capability for more frequent plume releases

CMAQv4.5 & v4.5.1 Highlights (continued)

• Dynamic allocation of vertical layers Enables same executable to be used for different vertical

grid configurations

• Parallel I/O Added worker and I/O processors partition scheme

• Diagnostic Tools Sulfate and primary carbon tracking Process Analysis

• Updated for latest version of model processes

• MCIP Add capability for WRF-ARW Dry dep. velocities for chlorine and mercury

Notes:• TCDiesel ≈ 5 × TCGasoline

• Both source categories track population density

Diagnostic Tools – Carbon Tracking

Fine Carbon from Diesel Exhaust Fine Carbon from Gasoline Exhaust

Notes:• TCBiomass is dominated by wildfires• TCFood tracks population density

TC2.5 from Biomass Combustion TC2.5 from Food Cooking

Diagnostic Tools – Carbon Tracking

Diagnostic Tools – Sulfate Tracking

All scales represent the fraction of total aerosol sulfate.

CMAQv4.6 Features

Model Upgrades for 2006

• Aerosols Updated ISORROPIA to v1.7

• Includes correction in activity coefficients for temperatures other than 298 K

• Ammonium nitrate aerosol concentrations increase somewhat

Revised to use T, RH-dependent “gamma” (heterogeneous N2O5 reaction probability) from Evans & Jacob (2005)

• Net production of nitrate decreases in the winter and increases slightly in the summer

Upper limit set for the RH input to ISORROPIA (95%)• Sets limits on the aerosol water concentrations

– Previous versions of CMAQ could have water concentrations as high as 1000 ug/m3

Updated parameters in the aerosol diagnostic file

• Chemistry New Carbon Bond (CB05) mechanism and

associated EBI solver• Summer ozone concentrations are about 8% higher

compared with the CB4 mechanism Include the gas-phase reactions involving N2O5

and H2O• Increases aerosol nitrate concentrations

Removed obsolete mechanism combinations (e.g. gas+aerosols w/o aqueous)

• Carbon Apportionment and Sulfate Tracking Added capability for CB05 (and AE4) mechanisms

CMAQv4.6 Upgrades (cont.)

Chemical Mechanisms: CMAQv4.6

CMAQv4.6 Upgrades (cont.)

• PBL modeling New ACM2: combined non-local and local closure

scheme• Produces different vertical profiles of pollutants in the

convective boundary layer (CBL)• Effective CBL mixing layer is shallower than for EDDY• Ground-level O3 concentrations slightly higher,

especially in the late afternoon• Precursors emitted at ground level tend to have lower

concentrations with more well mixed profiles in the CBL• Little effect on ground-level aerosol concentrations

• Plume-in-Grid Capability for AE4 mechanisms

CMAQv4.6 Upgrades (cont.)

• Circular buffer CGRID state file Write restart file

• Permits flexibility in the “CONC” file (write subset of species and layers)

• Parallel I/O Various updates (new version required for

CMAQv4.6 compilation)

Release Schedule

• CMAS will release CMAQv4.6 to the public in September/October 2006 Science description of new features Will include a model evaluation report Test datasets

Future Work

• Develop on-line coupling capability for WRF-CMAQ Allow aerosol feedback to radiation model Closer temporal coupling between

meteorology and chemistry Integrated resolved-scale microphysics and

aqueous chemistry Aerosol effects on microphysics

Work in progress

Work in progress (cont.)

• Aerosols Gas-phase interactions with coarse-mode sea salt Incorporate a new SOA module for oxidation of

aromatic, isoprene, and monoterpene mixtures

• Photolysis New in-line photolysis model for CMAQ

• Hybrid of TUV (Madronich) and Fast-J (Prather)• 7 wavelength bands in UV and visible• Updated absorption cross-sections and quantum yields• Includes extinction and scattering by CMAQ aerosols• Effects of clouds will be added to on-line calculations

• Cloud modeling Collaboration with NOAA to adapt WRF/CHEM

convective cloud model for CMAQ • CMAQ aqueous chemistry module• Wet deposition

Generalized aqueous chemistry solver• Develop operational satellite assimilation for

Surface insolation Photolysis rates Skin temperature nudging for soil moisture Cloud dynamics

Work in progress (cont.)

CMAQ Model Limitations

• Errors/uncertainties in input data Initial and boundary conditions Meteorology Emissions

• Gaps or incomplete understanding in process details or mathematical representations (e.g. VOC chemistry modeled using a lumped mechanism)

CMAQ Model Limitations (cont.)

• Issues of horizontal scale Regional through urban modeling domains

• Typical grid cell sizes: 1-40 km Scale-dependent process parameterizations

• For grid cell sizes >40 km:– Grid averaging can significantly affect results– Misrepresentation of emissions/chemistry at this scale

• For grid cell sizes <1 km:– Resolving explicit atmospheric turbulence– Model parameterizations break down– Requires different modeling approaches

(e.g. LES, CFD)

Concluding Remarks

• CMAQ and similar models are required tools for air quality planning

• Such air quality models represent a complex atmospheric system, with uncertainties in each system component Research is conducted using the models as

“numerical laboratories”, in conjunction with laboratory and field data, to reduce the component uncertainties

Concluding Remarks (cont.)

• Modeling applications Regulatory assessments of O3, PM2.5,

air toxics, mercury Acid/nutrient deposition AQ/climate interactions

Acknowledgements

DisclaimerDisclaimer: The research presented here was performed under the : The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce’s National Oceanic and Agency (EPA) and the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA) and under agreement number Atmospheric Administration (NOAA) and under agreement number DW13921548. This work constitutes a contribution to the NOAA Air Quality DW13921548. This work constitutes a contribution to the NOAA Air Quality Program. Although it has been reviewed by EPA and NOAA and approved for Program. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their views or policies.publication, it does not necessarily reflect their views or policies.

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