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| Titel |
Airborne measurement of OH reactivity during INTEX-B |
| VerfasserIn |
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 |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 1 ; Nr. 9, no. 1 (2009-01-12), S.163-173 |
| Datensatznummer |
250006637
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| Publikation (Nr.) |
 copernicus.org/acp-9-163-2009.pdf |
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| Zusammenfassung |
| 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 outflow 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 −Δln(signal)/Δ 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 reactivity
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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