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| Titel |
Modeling chemistry in and above snow at Summit, Greenland: Impact of snowpack chemistry on the oxidation capacity of the boundary layer |
| VerfasserIn |
J. L. Thomas, J. Dibb, G. Huey, J. Liao, D. Tanner, B. Lefer, R. von Glasow, J. Stutz |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250065747
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| Zusammenfassung |
| The chemical composition of the boundary layer in snow covered regions is impacted by
chemistry in the snowpack via uptake, processing, and emission of atmospheric trace gases.
We use the coupled one-dimensional snow chemistry and atmospheric boundary layer model
MISTRA-SNOW to study the impact of snowpack chemistry on the oxidation capacity of the
boundary layer. The model includes gas phase photochemistry and chemical reactions both in
the 5 interstitial air and the atmosphere. Chemistry on snow grains is simulated
assuming a liquid-like layer (LLL), treated as an aqueous layer on the snow grain
surface. The model has been recently compared with BrO and NO data taken on June
10 - June 13, 2008 as part of the Greenland Summit Halogen-HOx experiment
(GSHOX). In the present study, we use the same focus period to investigate the influence
10 of snowpack derived chemistry on OH and HOx+RO2 in the boundary layer.
We compare model results with chemical ionization mass spectrometry (CIMS)
measurements of the hydroxyl radical (OH) and of the hydroperoxyl radical (HO2)
plus the sum of all organic peroxy radicals (RO2) taken at Summit during summer
2008. Using sensitivity runs we show that snowpack influenced nitrogen cycling
and bromine chemistry both increase the oxidation capacity of the boundary layer
and that 15 together they increase the mid-day OH concentrations by a factor of
~2. We show for the first time, using an unconstrained coupled one-dimensional
snowpack-boundary layer model, that air-snow interactions impact the oxidation capacity of
the boundary layer and that it is not possible to match measured OH levels without
snowpack NOx and halogen emissions. Model predicted HONO compared with
mistchamber measurements suggests there is a large unknown HONO source at Summit.
Other model predicted HOx precursors, H2O2 and HCHO, compare well with 20
measurements taken in summer 2000. Snow sourced NOx contributes an additional 2
ppb of boundary layer ozone over 3 days, while snow sourced bromine has the
opposite effect and contributes 1 ppb of boundary layer ozone loss over 3 days. |
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