Verification of a source-oriented externally mixed air quality model during a severe photochemical smog episode

Qi Ying, Matthew Fraser, Robert J. Griffin, Jianjun Chen, Michael J. Kleeman

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The CIT/UCD three-dimensional source-oriented externally mixed air quality model is tested during a severe photochemical smog episode (Los Angeles, 7-9 September 1993) using two different chemical mechanisms that describe the formation of ozone and secondary reaction products. The first chemical mechanism is the secondary organic aerosol mechanism (SOAM) that is based on SAPRC90 with extensions to describe the formation of condensable organic products. The second chemical mechanism is the caltech atmospheric chemistry mechanism (CACM) that is based on SAPRC99 with more detailed treatment of organic oxidation products. The predicted ozone concentrations from the CIT/UCD/SOAM and the CIT/UCD/CACM models agree well with the observations made at most monitoring sites with a mean normalized error of approximately 0.4-0.5. Good agreement is generally found between the predicted and measured NOx concentrations except during morning rush hours of 6-10 am when NOx concentrations are under-predicted at most locations. Total VOC concentrations predicted by the two chemical mechanisms agree reasonably well with the observations at three of the four sites where measurements were made. Gas-phase concentrations of phenolic compounds and benzaldehyde predicted by the UCD/CIT/CACM model are higher than the measured concentrations whereas the predicted concentrations of other aromatic compounds approximately agree with the measured values. The fine airborne particulate matter mass concentrations (PM2.5) predicted by the UCD/CIT/SOAM and UCD/CIT/CACM models are slightly greater than the observed values during evening hours and lower than observed values during morning rush hours. The evening over-predictions are driven by an excess of nitrate, ammonium ion and sulfate. The UCD/CIT/CACM model predicts higher nighttime concentrations of gaseous precursors leading to the formation of particulate nitrate than the UCD/CIT/SOAM model. Elemental carbon and total organic mass are under-predicted by both models during morning rush hour periods. When this latter finding is combined with the NOx under-predictions that occur at the same time, it suggests a systematic bias in the diesel engine emissions inventory. The mass of particulate total organic carbon is under-predicted by both the UCD/CIT/SOAM and UCD/CIT/CACM models during afternoon hours. Elemental carbon concentrations generally agree with the observations at this time. Both the UCD/CIT/SOAM and UCD/CIT/CACM models predict low concentrations of secondary organic aerosol (SOA) (<3.5 μg m-3) indicating that both models could be missing SOA formation pathways. The representation of the aerosol as an internal mixture vs. a source-oriented external mixture did not significantly affect the predicted concentrations during the current study.

Original languageEnglish (US)
Pages (from-to)1521-1538
Number of pages18
JournalAtmospheric Environment
Volume41
Issue number7
DOIs
StatePublished - Mar 2007
Externally publishedYes

Fingerprint

Air quality
Atmospheric chemistry
air quality
Aerosols
atmospheric chemistry
aerosol
Ozone
Nitrates
ozone
photochemical smog
Carbon
aerosol formation
Aromatic compounds
carbon
diesel engine
emission inventory
phenolic compound
ammonium nitrate
Organic carbon
prediction

Keywords

  • CACM
  • Los Angeles
  • SAPRC90
  • UCD/CIT source-oriented air quality model

ASJC Scopus subject areas

  • Atmospheric Science
  • Environmental Science(all)
  • Pollution

Cite this

Verification of a source-oriented externally mixed air quality model during a severe photochemical smog episode. / Ying, Qi; Fraser, Matthew; Griffin, Robert J.; Chen, Jianjun; Kleeman, Michael J.

In: Atmospheric Environment, Vol. 41, No. 7, 03.2007, p. 1521-1538.

Research output: Contribution to journalArticle

Ying, Qi ; Fraser, Matthew ; Griffin, Robert J. ; Chen, Jianjun ; Kleeman, Michael J. / Verification of a source-oriented externally mixed air quality model during a severe photochemical smog episode. In: Atmospheric Environment. 2007 ; Vol. 41, No. 7. pp. 1521-1538.
@article{2e916669adda4c6794c99b33f2701684,
title = "Verification of a source-oriented externally mixed air quality model during a severe photochemical smog episode",
abstract = "The CIT/UCD three-dimensional source-oriented externally mixed air quality model is tested during a severe photochemical smog episode (Los Angeles, 7-9 September 1993) using two different chemical mechanisms that describe the formation of ozone and secondary reaction products. The first chemical mechanism is the secondary organic aerosol mechanism (SOAM) that is based on SAPRC90 with extensions to describe the formation of condensable organic products. The second chemical mechanism is the caltech atmospheric chemistry mechanism (CACM) that is based on SAPRC99 with more detailed treatment of organic oxidation products. The predicted ozone concentrations from the CIT/UCD/SOAM and the CIT/UCD/CACM models agree well with the observations made at most monitoring sites with a mean normalized error of approximately 0.4-0.5. Good agreement is generally found between the predicted and measured NOx concentrations except during morning rush hours of 6-10 am when NOx concentrations are under-predicted at most locations. Total VOC concentrations predicted by the two chemical mechanisms agree reasonably well with the observations at three of the four sites where measurements were made. Gas-phase concentrations of phenolic compounds and benzaldehyde predicted by the UCD/CIT/CACM model are higher than the measured concentrations whereas the predicted concentrations of other aromatic compounds approximately agree with the measured values. The fine airborne particulate matter mass concentrations (PM2.5) predicted by the UCD/CIT/SOAM and UCD/CIT/CACM models are slightly greater than the observed values during evening hours and lower than observed values during morning rush hours. The evening over-predictions are driven by an excess of nitrate, ammonium ion and sulfate. The UCD/CIT/CACM model predicts higher nighttime concentrations of gaseous precursors leading to the formation of particulate nitrate than the UCD/CIT/SOAM model. Elemental carbon and total organic mass are under-predicted by both models during morning rush hour periods. When this latter finding is combined with the NOx under-predictions that occur at the same time, it suggests a systematic bias in the diesel engine emissions inventory. The mass of particulate total organic carbon is under-predicted by both the UCD/CIT/SOAM and UCD/CIT/CACM models during afternoon hours. Elemental carbon concentrations generally agree with the observations at this time. Both the UCD/CIT/SOAM and UCD/CIT/CACM models predict low concentrations of secondary organic aerosol (SOA) (<3.5 μg m-3) indicating that both models could be missing SOA formation pathways. The representation of the aerosol as an internal mixture vs. a source-oriented external mixture did not significantly affect the predicted concentrations during the current study.",
keywords = "CACM, Los Angeles, SAPRC90, UCD/CIT source-oriented air quality model",
author = "Qi Ying and Matthew Fraser and Griffin, {Robert J.} and Jianjun Chen and Kleeman, {Michael J.}",
year = "2007",
month = "3",
doi = "10.1016/j.atmosenv.2006.10.004",
language = "English (US)",
volume = "41",
pages = "1521--1538",
journal = "Atmospheric Environment",
issn = "0004-6981",
publisher = "Pergamon Press Ltd.",
number = "7",

}

TY - JOUR

T1 - Verification of a source-oriented externally mixed air quality model during a severe photochemical smog episode

AU - Ying, Qi

AU - Fraser, Matthew

AU - Griffin, Robert J.

AU - Chen, Jianjun

AU - Kleeman, Michael J.

PY - 2007/3

Y1 - 2007/3

N2 - The CIT/UCD three-dimensional source-oriented externally mixed air quality model is tested during a severe photochemical smog episode (Los Angeles, 7-9 September 1993) using two different chemical mechanisms that describe the formation of ozone and secondary reaction products. The first chemical mechanism is the secondary organic aerosol mechanism (SOAM) that is based on SAPRC90 with extensions to describe the formation of condensable organic products. The second chemical mechanism is the caltech atmospheric chemistry mechanism (CACM) that is based on SAPRC99 with more detailed treatment of organic oxidation products. The predicted ozone concentrations from the CIT/UCD/SOAM and the CIT/UCD/CACM models agree well with the observations made at most monitoring sites with a mean normalized error of approximately 0.4-0.5. Good agreement is generally found between the predicted and measured NOx concentrations except during morning rush hours of 6-10 am when NOx concentrations are under-predicted at most locations. Total VOC concentrations predicted by the two chemical mechanisms agree reasonably well with the observations at three of the four sites where measurements were made. Gas-phase concentrations of phenolic compounds and benzaldehyde predicted by the UCD/CIT/CACM model are higher than the measured concentrations whereas the predicted concentrations of other aromatic compounds approximately agree with the measured values. The fine airborne particulate matter mass concentrations (PM2.5) predicted by the UCD/CIT/SOAM and UCD/CIT/CACM models are slightly greater than the observed values during evening hours and lower than observed values during morning rush hours. The evening over-predictions are driven by an excess of nitrate, ammonium ion and sulfate. The UCD/CIT/CACM model predicts higher nighttime concentrations of gaseous precursors leading to the formation of particulate nitrate than the UCD/CIT/SOAM model. Elemental carbon and total organic mass are under-predicted by both models during morning rush hour periods. When this latter finding is combined with the NOx under-predictions that occur at the same time, it suggests a systematic bias in the diesel engine emissions inventory. The mass of particulate total organic carbon is under-predicted by both the UCD/CIT/SOAM and UCD/CIT/CACM models during afternoon hours. Elemental carbon concentrations generally agree with the observations at this time. Both the UCD/CIT/SOAM and UCD/CIT/CACM models predict low concentrations of secondary organic aerosol (SOA) (<3.5 μg m-3) indicating that both models could be missing SOA formation pathways. The representation of the aerosol as an internal mixture vs. a source-oriented external mixture did not significantly affect the predicted concentrations during the current study.

AB - The CIT/UCD three-dimensional source-oriented externally mixed air quality model is tested during a severe photochemical smog episode (Los Angeles, 7-9 September 1993) using two different chemical mechanisms that describe the formation of ozone and secondary reaction products. The first chemical mechanism is the secondary organic aerosol mechanism (SOAM) that is based on SAPRC90 with extensions to describe the formation of condensable organic products. The second chemical mechanism is the caltech atmospheric chemistry mechanism (CACM) that is based on SAPRC99 with more detailed treatment of organic oxidation products. The predicted ozone concentrations from the CIT/UCD/SOAM and the CIT/UCD/CACM models agree well with the observations made at most monitoring sites with a mean normalized error of approximately 0.4-0.5. Good agreement is generally found between the predicted and measured NOx concentrations except during morning rush hours of 6-10 am when NOx concentrations are under-predicted at most locations. Total VOC concentrations predicted by the two chemical mechanisms agree reasonably well with the observations at three of the four sites where measurements were made. Gas-phase concentrations of phenolic compounds and benzaldehyde predicted by the UCD/CIT/CACM model are higher than the measured concentrations whereas the predicted concentrations of other aromatic compounds approximately agree with the measured values. The fine airborne particulate matter mass concentrations (PM2.5) predicted by the UCD/CIT/SOAM and UCD/CIT/CACM models are slightly greater than the observed values during evening hours and lower than observed values during morning rush hours. The evening over-predictions are driven by an excess of nitrate, ammonium ion and sulfate. The UCD/CIT/CACM model predicts higher nighttime concentrations of gaseous precursors leading to the formation of particulate nitrate than the UCD/CIT/SOAM model. Elemental carbon and total organic mass are under-predicted by both models during morning rush hour periods. When this latter finding is combined with the NOx under-predictions that occur at the same time, it suggests a systematic bias in the diesel engine emissions inventory. The mass of particulate total organic carbon is under-predicted by both the UCD/CIT/SOAM and UCD/CIT/CACM models during afternoon hours. Elemental carbon concentrations generally agree with the observations at this time. Both the UCD/CIT/SOAM and UCD/CIT/CACM models predict low concentrations of secondary organic aerosol (SOA) (<3.5 μg m-3) indicating that both models could be missing SOA formation pathways. The representation of the aerosol as an internal mixture vs. a source-oriented external mixture did not significantly affect the predicted concentrations during the current study.

KW - CACM

KW - Los Angeles

KW - SAPRC90

KW - UCD/CIT source-oriented air quality model

UR - http://www.scopus.com/inward/record.url?scp=33846466682&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33846466682&partnerID=8YFLogxK

U2 - 10.1016/j.atmosenv.2006.10.004

DO - 10.1016/j.atmosenv.2006.10.004

M3 - Article

AN - SCOPUS:33846466682

VL - 41

SP - 1521

EP - 1538

JO - Atmospheric Environment

JF - Atmospheric Environment

SN - 0004-6981

IS - 7

ER -