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| Titel |
Airborne DOAS measurements of aerosol extinction and NO2 profiles in Arctic: two cases studies and their transport interpetation |
| VerfasserIn |
Alexis Merlaud, Nicolas Theys, Boris Quennehen, Alfons Schwarzenboeck, Matthieu Pommier, Gérard Ancellet, John F. Burkhart, Andreas Stohl, Michel Van Roozendael |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056679
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| Zusammenfassung |
| We present airborne DOAS measurements of aerosol extinction and NO2 tropospheric profiles
measured over the sea along the North coast of Norway during the POLARCAT-France
spring campaign. The DOAS instrument was installed on the French Safire ATR-42 aircraft
and measured scattered light spectra in near-limb geometry using a scanning telescope. This
configuration achieves both high sensitivity and fine vertical resolution when the
plane performs vertical soundings. Profile retrievals are based on the maximum a
posteriori method, for which we compare a linear and a logarithmic approach. We use
O4 slant column measurements to derive the aerosol extinction at 360 nm. The
result is compared with extinction calculated from simultaneous in-situ measured
size distribution. Two soundings are presented, one performed on 8 April 2008
at 71°N, 22°E and a second on 9 April 2008 at 70°N, 17.8°E. The first profile
shows aerosol extinction and NO2 in the marine boundary layer with respective
values of 0.04±0.005 km-1 and 1.9±0.3 x 109 molec/cm3. A second extinction
layer of 0.01±0.003 km-1 is found at 4 km altitude. During the second sounding,
clouds prevented retrievals below 3 km altitude but a layer with enhanced extinction
(0.025±0.005 km-1) and NO2 (1.95±0.2 x 109 molec/cm3) is clearly detected at 4 km
altitude.
From CO and ozone in-situ measurements complemented by FLEXPART retroplume
products, we interpret the measurements in the free troposphere as, for the first sounding, a
mix between stratospheric and polluted air from Northern Europe and for the second
sounding, polluted air from Central Europe containing NO2. Cold temperatures in the
troposphere enabled the transport of this short-lived compound. Considering the boundary
layer measurements, modeled source regions indicate closer sources, especially the Kola
Peninsula smelters, which can explain the NO2 enhancement not correlated with a CO
increase at the same altitude. |
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