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Airborne Measurement of Oh Reactivity During Intex-b : Volume 9, Issue 1 (12/01/2009)

By Mao, J.

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Book Id: WPLBN0003989526
Format Type: PDF Article :
File Size: Pages 11
Reproduction Date: 2015

Title: Airborne Measurement of Oh Reactivity During Intex-b : Volume 9, Issue 1 (12/01/2009)  
Author: Mao, J.
Volume: Vol. 9, Issue 1
Language: English
Subject: Science, Atmospheric, Chemistry
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Historic
Publication Date:
2009
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

Citation

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Shetter, R. E., Ren, X., Olson, J. R., Mao, J., Crawford, J. H., Singh, H. B.,...Cohen, R. C. (2009). Airborne Measurement of Oh Reactivity During Intex-b : Volume 9, Issue 1 (12/01/2009). Retrieved from http://www.ebooklibrary.org/


Description
Description: Department of Meteorology, Pennsylvania State University, University Park, PA, USA. 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.

Summary
Airborne measurement of OH reactivity during INTEX-B

Excerpt
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