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| Titel |
A Synopsis of CALIPSO PSC Observations from 2006-2014 |
| VerfasserIn |
Lamont Poole, Michael Pitts |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088825
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| Publikation (Nr.) |
 EGU/EGU2014-2988.pdf |
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| Zusammenfassung |
| Polar stratospheric clouds (PSCs) are known to play key roles in the springtime chemical
depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or
STS droplets) provide sites for heterogeneous chemical reactions that transform stable
chlorine and bromine reservoir species into highly reactive ozone-destructive forms.
Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute
odd nitrogen through gravitational sedimentation (a process commonly known as
denitrification), which prolongs the ozone depletion process by slowing the reformation
of the stable chlorine reservoirs. The observational database on PSCs has been
augmented tremendously in recent years by data from the polarization-sensitive
CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) lidar system onboard the
CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations)
spacecraft.
CALIOP began data collection in mid-June 2006 and has since acquired, on average, over
300,000 backscatter profiles daily at latitudes between 55o and 82o in both hemispheres.
PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging
scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible
spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low
number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are also
separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the
ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm
particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT
and ice particles). The composition classification scheme has been modified recently to
account for denitrification, the primary effect of which is the misclassification of ice
clouds as liquid/NAT mixtures. This paper will use these CALIOP observations to
examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on
vortex-wide scales for entire PSC seasons over the nearly eight-year data record. |
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