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| Titel |
Starphotometry at two High Arctic stations. |
| VerfasserIn |
Konstantin Baibakov, Norm O'Neill, Andreas Herber, Christoph Ritter, Karl-Heinz Schulz, Otto Schrems |
| 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 |
250046166
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| Zusammenfassung |
| Aerosols can significantly alter the Arctic’s delicate radiative balance, both directly by
absorbing and scattering solar and terrestrial radiation, and indirectly by influencing cloud
properties through their critical role as cloud condensation nuclei. Aerosol optical depth
(AOD), a multi-spectral indicator of the total vertical extinction due to atmospheric aerosols,
is one of the most important (aerosol) radiative forcing parameters. During the
day, it is traditionally measured using the well-known sunphotometry technique.
Night-time AOD measurements at all latitudes are very scarce; this data gap is especially
critical in the Arctic where the sun-free Polar winter lasts about 6 months. Recently
developed starphotometry techniques based on extinction measurements of bright-star
radiation help to mitigate the lack of any type consistent and regular Polar Night
measurements.
Two starphotometers (denoted as SP-NY and SP-EU respectively) are currently installed
in the Arctic region: at Ny Alesund (Spitsbergen, 78Ë 55"N, 11Ë 55"E) and Eureka, Canada
(79Ë 59’N, 85Ë 56’W). SP-NY has been in operation since 1995 and together with
sunphotometry has provided day-night (summer to winter) AOD-derived indicators of
multiyear aerosol dynamics at Ny Alesund. SP-EU has been in limited operation since 2008.
Key sunphotometry parameters such as multi-band AOD, Angstrom exponent and fine-mode
(sub-micron) and coarse-mode (super-micron) optical depth can be derived from the star
extinction measurements. It is useful to co-locate starphotometers with other optical and
microphysical instruments (zenith-pointing lidars and total sky imagers being examples of the
former) as this enables optical consistency checks and correlation analysis between different
types of data.
Since Oct-Nov 2010, both starphotometers (and, in the case of Eureka, starphotometer’s
mount and dome) were upgraded to become essentially identical in the way they acquire and
process stars’ spectra. We will summarize the preliminary analyses of the AOD
measurements acquired with SP-NY in the recent years. We will also present initial
comparisons between SP-NY and SP-EU during the 2010-11 Polar winter - the first time both
instruments operate simultaneously. |
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