Comparison of measured OH concentrations with model calculations

Poppe, D.; Zimmermann, Jörg; Bauer, R.; Brauers, T.; Brüning, D.; Callies, J.; Dorn, Hans-Peter; Hofzumahaus, A.; Johnen, F. J.; Khedim, A.; Koch, H.; Koppmann, R.; London, H.; Müller, Klaus Peter; Neuroth, R.; Plaß-Dülmer, C.; Platt, U.; Rohrer, Franz; Roth, E.; Rudolph, J.; Schmidt, Ulrich; Wallasch, Markus; Ehhalt, D. H.

doi:10.1029/94jd00378

Cited by 61 publications

(29 citation statements)

References 33 publications

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“…Owing to their short lifetimes, OH and HO2 react quickly to changes in local ambient conditions (solar flux, concentration of NOx, and NMHC) but are unaffected by transport. It is therefore sufficient to use a zero-dimensional model with no spatial resolution to describe the fast chemical processes [Poppe et al, 1994]. In order to make the model meaningful, frequent measurements of ancillary data in the same air parcel are required, as was the case during EASE96.…”

Section: Model Descriptionmentioning

confidence: 99%

Modeling OH, HO₂, and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

Carslaw¹,

Creasey²,

Heard³

et al. 1999

J. Geophys. Res.

143

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Section: Model Descriptionmentioning

confidence: 99%

Modeling OH, HO₂, and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

Carslaw¹,

Creasey²,

Heard³

et al. 1999

J. Geophys. Res.

143

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“…In order to ascertain how well we understand these OH initiated photochemical processes, measured ambient OH radical concentrations from field studies are often compared with OH radical concentrations predicted by photochemical models (e.g. Poppe et al, 1994;Hofzumahaus et al, 1996;Carslaw et al, 2002;Holland et al, 2003;Martinez et al, 2003;Olson et al, 2004;Ren et al, 2005;Ren et al, 2006;Smith et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

The Comparative Reactivity Method – a new tool to measure total OH Reactivity in ambient air

et al. 2008

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Abstract. Hydroxyl (OH) radicals play a vital role in maintaining the oxidizing capacity of the atmosphere. To understand variations in OH radicals both source and sink terms must be understood. Currently the overall sink term, or the total atmospheric reactivity to OH, is poorly constrained.Here, we present a new on-line method to directly measure the total OH reactivity (i.e. total loss rate of OH radicals) in a sampled air mass. In this method, a reactive molecule (X), not normally present in air, is passed through a glass reactor and its concentration is monitored with a suitable detector. OH radicals are then introduced in the glass reactor at a constant rate to react with X, first in the presence of zero air and then in the presence of ambient air containing VOCs and other OH reactive species. Comparing the amount of X exiting the reactor with and without the ambient air allows the air reactivity to be determined. In our existing set up, X is pyrrole and the detector used is a proton transfer reaction mass spectrometer. The present dynamic range for ambient air reactivity is about 6 to 300 s −1 , with an overall maximum uncertainty of 25% above 8 s −1 and up to 50% between 6-8 s −1 . The system has been tested and calibrated with different single and mixed hydrocarbon standards showing excellent linearity and accountability with the reactivity of the standards. Potential interferences such as high NO in ambient air, varying relative humidity and photolysis of pyrrole within the setup have also been investigated. While interferences due changing humidity and photolysis of pyrrole are easily overcome by ensuring that humidity in the set up does not change drastically and the photolytic loss of pyrrole is measured and taken into account, respectively, NO>10 ppb in ambient air remains a significant interference for the current configuration of the instrument. Field tests in the tropical rainforest of Suriname (∼53 s −1 ) and the urban atmosphere Correspondence to: J. Williams (williams@mpch-mainz.mpg.de) of Mainz (∼10 s −1 ) Germany, show the promise of the new method and indicate that a significant fraction of OH reactive species in the tropical forests is likely missed by current measurements. Suggestions for improvements to the technique and future applications are discussed.

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“…HCHO and CH 3 CHO, can be a significant source of peroxy radicals (e.g. Poppe et al, 1994;Carslaw et al, 2002) and by the conversion of the H atom generated in Reaction 7 following Reaction 4. A further source of peroxy radicals is the oxidation of alkenes by the nitrate radical, NO 3 , and a small yield from the oxidation of alkenes by ozone.…”

Section: Introductionmentioning

confidence: 99%

Hohenpeissenberg Photochemical Experiment (HOPE 2000): Measurements and photostationary state calculations of OH and peroxy radicals

Handisides¹,

Plaß-Dülmer

Gilge

et al. 2003

Atmos. Chem. Phys.

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Abstract. Measurements of OH, total peroxy radicals, nonmethane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5×10 6 molecules cm −3 and 7.4×10 6 molecules cm −3 . The maximum total RO x (RO x =OH+RO+HO 2 +RO 2 ) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14×10 6 molecules cm −3 s −1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO 2 and RO 2 . The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO 2 /RO 2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO 2 radicals to OH. This reaction was responsible for the recycling of more than 45×10 6 molecules cm −3 s −1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes.

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Comparison of measured OH concentrations with model calculations

Cited by 61 publications

References 33 publications

Modeling OH, HO₂, and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

Modeling OH, HO₂, and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

The Comparative Reactivity Method – a new tool to measure total OH Reactivity in ambient air

Hohenpeissenberg Photochemical Experiment (HOPE 2000): Measurements and photostationary state calculations of OH and peroxy radicals

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Comparison of measured OH concentrations with model calculations

Cited by 61 publications

References 33 publications

Modeling OH, HO2, and RO2 radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

Modeling OH, HO2, and RO2 radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

The Comparative Reactivity Method – a new tool to measure total OH Reactivity in ambient air

Hohenpeissenberg Photochemical Experiment (HOPE 2000): Measurements and photostationary state calculations of OH and peroxy radicals

Contact Info

Product

Resources

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Modeling OH, HO₂, and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with field measurements

Modeling OH, HO₂, and RO₂ radicals in the marine boundary layer: 1. Model construction and comparison with field measurements