Measurements of CH 3 O 2 NO 2 in the upper troposphere

• Published in: Atmospheric measurement techniques Vol. 8; no. 2; pp. 987 - 997
• Main Authors: Nault, B. A., Garland, C., Pusede, S. E., Wooldridge, P. J., Ullmann, K., Hall, S. R., Cohen, R. C.
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 27.02.2015
• Subjects: Accuracy; Aircraft; Atmospheric chemistry; Atmospheric composition; Clouds; Convective clouds; Detection; Dissociation; Fluorescence; Interference; Laser induced fluorescence; Lasers; Low temperature; Nitrogen dioxide; Photochemistry; Specificity; Surveys; Troposphere; Upper troposphere
• ISSN: 1867-8548; 1867-1381; 1867-8548
• DOI: 10.5194/amt-8-987-2015

Methyl peroxy nitrate (CH3O2NO2) is a non-acyl peroxy nitrate that is important for photochemistry at low temperatures characteristic of the upper troposphere. We report the first measurements of CH3O2NO2, which we achieved through a new aircraft inlet configuration, combined with thermal-dissociation laser-induced fluorescence (TD-LIF) detection of NO2, and describe the accuracy, specificity, and interferences to CH3O2NO2 measurements. CH3O2NO2 is predicted to be a ubiquitous interference to upper-tropospheric NO2 measurements. We describe an experimental strategy for obtaining NO2 observations free of the CH3O2NO2 interference. Using these new methods, we made observations during two recent aircraft campaigns: the Deep Convective Clouds and Chemistry (DC-3) and the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) experiments. The CH3O2NO2 measurements we report have a detection limit (S/N = 2) of 15 pptv at 1 min averaging on a background of 200 pptv NO2 and an accuracy of ±40%. Observations are used to constrain the interference of pernitric acid (HO2NO2) to the CH3O2NO2 measurements, as HO2NO2 partially decomposes (~11%) along with CH3O2NO2 in the heated CH3O2NO2 channel used to detect CH3O2NO2.