Krish Vijayaraghavan, Prakash KaramchandaniChristian Seigneur

AERSan Ramon, CA

3rd Annual CMAS Models-3 ConferenceOctober 18-20, 2004

Chapel Hill, NC

Application of CMAQ-APT tothe Central California Ozone Study

Overview

• Limitations of 3-D grid modeling• CMAQ-APT: Plume-in-grid (PiG) air quality model

• State-of-the science treatment of stack plumes at the sub-grid scale

• 3-D grid host model - CMAQ• Reactive plume model – SCICHEM

• Impact of PiG treatment on ozone and HNO3 concentrations

Interface between CMAQ and SCICHEM

Domain, grid informationgeophysical datameteorological datadeposition velocities

CMAQ SCICHEM

Emissions,IC/BC

OutputOutput

puffinformation

Pointsource

emissions

Dumppuffs

chemicalconcentrations

chemicalconcentrations

I/OAPI

I/OAPI

I/OAPI

I/OAPI

StandardSCICHEM

output

Puff diagnostics (process analysis)

ControlFile

Improvements to CMAQ-APT

• Optional treatment for the effects of building downwash on plume rise and dispersion (PRIME)

• Incorporation of CMAQ code updates released in September 2003 (version 4.3)

• Incorporation of modifications in SCICHEM version 1601 (January 2004 release)

• Young & Boris chemistry solver

Application to Central California

• Central California Ozone Study (CCOS)

• Ozone episode: July 30 to August 1, 2000

• Study domain– 185 x 185 grid cells– Horizontal grid resolution of 4 km– 20 layers from surface to tropopause

(surface layer ~ 30 m)

Features of July/August 2000 CCOS episode

• Observed peak ozone during the modeling period was 134 ppb at San Andreas station on August 1, 2000

• Prevailing winds from the coast to the Central Valley

• Wildfires in the southeast (Tulare County near the Sierra Nevada)

Model Inputs

• Meteorology driven by MM5

• CMAQ emissions, initial and boundary conditions from CAMx files (ARB)

• 3-D gridded emissions using SMOKE plume rise processor

• Ten largest NOx emitting plants (with 56 stacks) selected for plume-in-grid (PiG) treatment

PiG Sources

Top 10 NOx emissions

1. Pittsburg power plant (16 Mg/day NOx)

2. Riverside Cement3. California Cement4. Moss Landing power plant5. Martinez refinery6. Hanson Cement7. Unknown8. Portland Cement9. IMC Chemicals10.Contra Costa power plant

Total = 101 Mg/day(4% of domain-wideNOx emissions)

Simulations

• CMAQ base simulation

– All emissions in domain in 3-D gridded format

• CMAQ background simulation– 3-D gridded emissions without PiG sources

• CMAQ-APT simulation– 3-D gridded emissions other than PiG sources– PiG sources treated separately with SCICHEM

ExtendedSan Francisco Bay Area

CMAQ Base: Surface Ozone 3 p.m. PDT on July 30, 2000

(Base – Background) Surface Ozone 3 p.m. PDT on July 30, 2000

(APT – Base) Surface Ozone 3 p.m. PDT on July 30, 2000

Evolution of Plume Chemistry

Early Plume Dispersion

NO/NO2/O3 chemistry

1

2

Mid-range Plume Dispersion

Reduced VOC/NOx/O3 chemistry — acid formation from OH and NO3/N2O5 chemistry

Long-range Plume Dispersion

3

Full VOC/NOx/O3 chemistry — acid and O3 formation

CMAQ Base: Surface HNO3

3 p.m. PDT on July 31, 2000

(Base – Background) Surface HNO3 3 p.m. PDT on July 31, 2000

(APT – Base) Surface HNO3 3 p.m. PDT on July 31, 2000

Comparison of CMAQ-APT results in CCOS and NARSTO

• CCOS– APT produces up to 10 ppb lower ozone than Base

and up to 1.5 ppb lower HNO3

• NARSTO– APT produces up to 40 ppb lower ozone than Base

and up to 24 ppb lower HNO3

(Karamchandani et al., J. Geophys. Res.,107, 4403, 2002)

• NOx emissions from PiG sources are about 50 times higher in NARSTO than in CCOS

Conclusions

• CMAQ-APT applied to July/August 2000 CCOS episode

• O3 concentrations using APT show both decrements (up to 10 ppb) and increments (up to 6 ppb) with respect to the base

• The VOC vs. NOx limited nature of the background environment explains the differences in O3 production and destruction between the APT and base results

Conclusions

• Surface HNO3 concentrations are up to 1.5 ppb (about 10%) lower in the CCOS APT simulation and 24 ppb lower in the NARSTO APT simulation, compared to the base cases

• Effect of PiG treatment on HNO3 is important for PM nitrate and regional haze modeling.

• PiG treatment for PM (CMAQ-MADRID-APT) is currently being tested (Karamchandani et al., AWMA, October 2004)

Acknowledgements

• California Energy Commission

• California Air Resources Board

• EPRI

• Titan/ARAP