Airborne measurement of OH reactivity during INTEX-B

J. Mao, X. Ren, W. H. Brune, J. R. Olson, J. H. Crawford, A. Fried, L. G. Huey, R. C. Cohen, B. Heikes, H. B. Singh, D. R. Blake, G. W. Sachse, G. S. Diskin, S. R. Hall, R. E. Shetter

Research output: Contribution to journalArticle

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Abstract

The measurement of OH reactivity, the inverse of the OH lifetime, provides a powerful tool to investigate atmospheric photochemistry. A new airborne OH reactivity instrument was designed and deployed for the first time on the NASA DC-8 aircraft during the second phase of Intercontinental Chemical Transport Experiment-B (INTEX-B) campaign, which was focused on the Asian pollution out-flow over Pacific Ocean and was based in Hawaii and Alaska. The OH reactivity was measured by adding OH, generated by photolyzing water vapor with 185 nm UV light in a moveable wand, to the flow of ambient air in a flow tube and measuring the OH signal with laser induced fluorescence. As the wand was pulled back away from the OH detector, the OH signal decay was recorded; the slope of-△ln(signal)/△ time was the OH reactivity. The overall absolute uncertainty at the 2σ confidence levels is about 1 s-1 at low altitudes (for decay about 6 s-1), and 0.7 s-1 at high altitudes (for decay about 2 s-1). From the median vertical profile obtained in the second phase of INTEX-B, the measured OH reactivity (4.0±1.0 s-1) is higher than the OH reactiv-ity calculated from assuming that OH was in steady state (3.3±0.8 s-1), and even higher than the OH reactivity that was calculated from the total measurements of all OH reactants (1.6±0.4 s-1). Model calculations show that the missing OH reactivity is consistent with the over-predicted OH and under-predicted HCHO in the boundary layer and lower troposphere. The over-predicted OH and under-predicted HCHO suggest that the missing OH sinks are most likely related to some highly reactive VOCs that have HCHO as an oxidation product.

Original languageEnglish (US)
Pages (from-to)163-173
Number of pages11
JournalAtmospheric Chemistry and Physics
Volume9
Issue number1
DOIs
StatePublished - Jan 8 2009

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laser induced fluorescence
experiment
photochemistry
ambient air
vertical profile
volatile organic compound
troposphere
water vapor
aircraft
outflow
boundary layer
oxidation
pollution
ocean
chemical
measuring
detector
calculation
product

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Mao, J., Ren, X., Brune, W. H., Olson, J. R., Crawford, J. H., Fried, A., ... Shetter, R. E. (2009). Airborne measurement of OH reactivity during INTEX-B. Atmospheric Chemistry and Physics, 9(1), 163-173. https://doi.org/10.5194/acp-9-163-2009
Mao, J. ; Ren, X. ; Brune, W. H. ; Olson, J. R. ; Crawford, J. H. ; Fried, A. ; Huey, L. G. ; Cohen, R. C. ; Heikes, B. ; Singh, H. B. ; Blake, D. R. ; Sachse, G. W. ; Diskin, G. S. ; Hall, S. R. ; Shetter, R. E. / Airborne measurement of OH reactivity during INTEX-B. In: Atmospheric Chemistry and Physics. 2009 ; Vol. 9, No. 1. pp. 163-173.
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abstract = "The measurement of OH reactivity, the inverse of the OH lifetime, provides a powerful tool to investigate atmospheric photochemistry. A new airborne OH reactivity instrument was designed and deployed for the first time on the NASA DC-8 aircraft during the second phase of Intercontinental Chemical Transport Experiment-B (INTEX-B) campaign, which was focused on the Asian pollution out-flow over Pacific Ocean and was based in Hawaii and Alaska. The OH reactivity was measured by adding OH, generated by photolyzing water vapor with 185 nm UV light in a moveable wand, to the flow of ambient air in a flow tube and measuring the OH signal with laser induced fluorescence. As the wand was pulled back away from the OH detector, the OH signal decay was recorded; the slope of-△ln(signal)/△ time was the OH reactivity. The overall absolute uncertainty at the 2σ confidence levels is about 1 s-1 at low altitudes (for decay about 6 s-1), and 0.7 s-1 at high altitudes (for decay about 2 s-1). From the median vertical profile obtained in the second phase of INTEX-B, the measured OH reactivity (4.0±1.0 s-1) is higher than the OH reactiv-ity calculated from assuming that OH was in steady state (3.3±0.8 s-1), and even higher than the OH reactivity that was calculated from the total measurements of all OH reactants (1.6±0.4 s-1). Model calculations show that the missing OH reactivity is consistent with the over-predicted OH and under-predicted HCHO in the boundary layer and lower troposphere. The over-predicted OH and under-predicted HCHO suggest that the missing OH sinks are most likely related to some highly reactive VOCs that have HCHO as an oxidation product.",
author = "J. Mao and X. Ren and Brune, {W. H.} and Olson, {J. R.} and Crawford, {J. H.} and A. Fried and Huey, {L. G.} and Cohen, {R. C.} and B. Heikes and Singh, {H. B.} and Blake, {D. R.} and Sachse, {G. W.} and Diskin, {G. S.} and Hall, {S. R.} and Shetter, {R. E.}",
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Mao, J, Ren, X, Brune, WH, Olson, JR, Crawford, JH, Fried, A, Huey, LG, Cohen, RC, Heikes, B, Singh, HB, Blake, DR, Sachse, GW, Diskin, GS, Hall, SR & Shetter, RE 2009, 'Airborne measurement of OH reactivity during INTEX-B', Atmospheric Chemistry and Physics, vol. 9, no. 1, pp. 163-173. https://doi.org/10.5194/acp-9-163-2009

Airborne measurement of OH reactivity during INTEX-B. / Mao, J.; Ren, X.; Brune, W. H.; Olson, J. R.; Crawford, J. H.; Fried, A.; Huey, L. G.; Cohen, R. C.; Heikes, B.; Singh, H. B.; Blake, D. R.; Sachse, G. W.; Diskin, G. S.; Hall, S. R.; Shetter, R. E.

In: Atmospheric Chemistry and Physics, Vol. 9, No. 1, 08.01.2009, p. 163-173.

Research output: Contribution to journalArticle

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T1 - Airborne measurement of OH reactivity during INTEX-B

AU - Mao, J.

AU - Ren, X.

AU - Brune, W. H.

AU - Olson, J. R.

AU - Crawford, J. H.

AU - Fried, A.

AU - Huey, L. G.

AU - Cohen, R. C.

AU - Heikes, B.

AU - Singh, H. B.

AU - Blake, D. R.

AU - Sachse, G. W.

AU - Diskin, G. S.

AU - Hall, S. R.

AU - Shetter, R. E.

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Y1 - 2009/1/8

N2 - The measurement of OH reactivity, the inverse of the OH lifetime, provides a powerful tool to investigate atmospheric photochemistry. A new airborne OH reactivity instrument was designed and deployed for the first time on the NASA DC-8 aircraft during the second phase of Intercontinental Chemical Transport Experiment-B (INTEX-B) campaign, which was focused on the Asian pollution out-flow over Pacific Ocean and was based in Hawaii and Alaska. The OH reactivity was measured by adding OH, generated by photolyzing water vapor with 185 nm UV light in a moveable wand, to the flow of ambient air in a flow tube and measuring the OH signal with laser induced fluorescence. As the wand was pulled back away from the OH detector, the OH signal decay was recorded; the slope of-△ln(signal)/△ time was the OH reactivity. The overall absolute uncertainty at the 2σ confidence levels is about 1 s-1 at low altitudes (for decay about 6 s-1), and 0.7 s-1 at high altitudes (for decay about 2 s-1). From the median vertical profile obtained in the second phase of INTEX-B, the measured OH reactivity (4.0±1.0 s-1) is higher than the OH reactiv-ity calculated from assuming that OH was in steady state (3.3±0.8 s-1), and even higher than the OH reactivity that was calculated from the total measurements of all OH reactants (1.6±0.4 s-1). Model calculations show that the missing OH reactivity is consistent with the over-predicted OH and under-predicted HCHO in the boundary layer and lower troposphere. The over-predicted OH and under-predicted HCHO suggest that the missing OH sinks are most likely related to some highly reactive VOCs that have HCHO as an oxidation product.

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