Statewide Protocol: Regional Application August 27, 2003 Air Resources Board California Environmental Protection Agency Luis F. Woodhouse

Regional Modeling Integrated Results Risk Assessment Mapping and Visualization Microscale Modeling Emissions and Meteorology Modeling Framework HARP CHAPIS 2

Objectives Simulate year 2000 air quality, including toxics, for all California using regional air quality models. Will provide background concentrations to be used with local dispersion modeling. 3

Previous Experience Modeled southern California for year 1998 –Air quality models: CMAQ and CALGRID –Meteorological models: MM5 and CALMET Developed annual model performance metrics (toxics and other species) Conducted sensitivity tests to expedite simulation while minimizing error introduced 4

Challenges for Statewide Modeling Very large modeling domain Potentially long run time (meteorological and regional models) Storage and processing of very large input and output files Evaluation of models input/output data Apply lessons learned to optimize statewide modeling Double counting 5

Optimizing Statewide Regional Modeling Apply lessons learned from previous experience modeling southern California –Shorter time periods to represent year –Use of subdomains to cover entire State Leveraging from other studies: –SCOS/CCOS/CRPAQS modeling and databases 6

Statewide Protocol: Regional Modeling Establishes criteria for conducting air quality modeling for toxic air pollutants: –Modeling domain definition –Selection and evaluation of models –Selection of chemical mechanism –Preparation of annual emissions inventory –Initial and boundary conditions –Evaluation of models results 7

Modeling Domain Ideal case Uses large modeling domain that includes entire state Resource intensive and requires long run time 8

Modeling Domain (cont.) For statewide simulation: Use 4 subdomains to cover state (4-km x 4-km grid) Each subdomain modeled independently Less resource intensive and faster run times for each subdomain SCOS subdomain by early

Air Quality Models Selection Sound scientific basis Reflect up-to-date-science Documentation Source code and technical documentation available to the public 10

Air Quality Models (cont.) For statewide simulation: State-of-the-science models will be evaluated (such as Models-3/CMAQ, CAMx and CALGRID) Criteria defined in protocol to evaluate model performance for ozone and toxics 11

Chemical Reaction Mechanism Selection Successful peer review Extensively tested Represents recent advances in science Publicly available 12

Chemical Reaction Mechanism (cont.) For statewide annual simulations: Selected SAPRC99 reaction mechanism Added explicit reactions for selected toxics 13

Toxics –1,3-butadiene –Formaldehyde –Acetaldehyde –Acrolein –Benzene –Carbon tetrachloride –Chloroform –Dichloromethane –1,2-Dichloroethane –o-Dichlorobenzene –p-Dichlorobenzene –Ethylene oxide –Perchloroethylene –Styrene –Toluene –Trichloroethylene –Vinyl Chloride –Xylenes –Diesel PM10 –Other PM10 species: Arsenic, Beryllium, Cadmium, Hexavalent Chromium, Iron, Lead, Manganese, Mercury, Nickel, Zinc and elemental carbon 14

Meteorological Model Selection Peer review process Fully documented Reflects recent advances in science Publicly available 15

Meteorology Models (cont.) For statewide modeling two meteorological models will be applied: –MM5: A prognostic model that predicts from first principles, mass and energy transfer equations –CALMET: A diagnostic model that uses observational data 16

Meteorological Models (Cont.) Evaluation of input and output data from meteorological models: –Overall pattern for selected periods –Predictions vs. observations for selected periods 17

Emissions Point and areawide emissions –Extrapolated from 1999 baseline –Use surrogates to allocate area sources to individual grids On-road motor vehicle emissions –Latest versions of EMFAC and DTIM4 require hourly temperature and relative humidity Biogenic emissions Weekday and weekend emissions by month 18

Emissions (cont.) Emissions will be evaluated before use in air quality models –Spatial pattern of emissions –Temporal patterns –Comparison of predicted and observed ratios of HC/NOx and CO/NOx 19

Initial and Boundary Conditions Protocol suggests default initial and constant boundary conditions –Boundary conditions same as for SCOS-97 Pristine over ocean (40 ppb O3, ppb NOx, and 20 ppbC VOC) South Coast clean over land (40 ppb O3, 2 ppb NOx, 60 ppbC VOC) 20

Summary Developed criteria for: –model selection –input preparation –input evaluation –model output evaluation Optimization of statewide modeling 21