 |
| Titel |
CALIPSO polar stratospheric cloud observations: second-generation detection algorithm and composition discrimination |
| VerfasserIn |
M. C. Pitts, L. R. Poole, L. W. Thomason |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 19 ; Nr. 9, no. 19 (2009-10-12), S.7577-7589 |
| Datensatznummer |
250007679
|
| Publikation (Nr.) |
 copernicus.org/acp-9-7577-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| This paper focuses on polar stratospheric cloud (PSC)
measurements by the CALIOP (Cloud-Aerosol LIdar with Orthogonal
Polarization) lidar system onboard the CALIPSO (Cloud-Aerosol Lidar and
Infrared Pathfinder Satellite Observations) spacecraft, which has been
operating since June 2006. We describe a second-generation PSC detection
algorithm that utilizes both the CALIOP 532-nm scattering ratio (ratio of
total-to-molecular backscatter coefficients) and 532-nm perpendicular
backscatter coefficient measurements for cloud detection. The inclusion of
the perpendicular backscatter measurements enhances the detection of tenuous
PSC mixtures containing low number densities of solid (likely nitric acid
trihydrate, NAT) particles and leads to about a 15% increase in PSC areal
coverage compared with our original algorithm. Although these low number
density NAT mixtures would have a minimal impact on chlorine activation due
to their relatively small particle surface area, these particles may play a
significant role in denitrification and therefore are an important component
of our PSC detection. In addition, the new algorithm allows discrimination
of PSCs by composition in terms of their ensemble backscatter and
depolarization in a manner analogous to that used in previous ground-based
and airborne lidar PSC studies. Based on theoretical optical calculations,
we define four CALIPSO-based composition classes which we call supercooled
ternary solution (STS), ice, and Mix1 and Mix2, denoting mixtures of STS
with NAT particles in lower or higher number densities/volumes,
respectively. We examine the evolution of PSCs for three Antarctic and two
Arctic seasons and illustrate the unique attributes of the CALIPSO PSC
database. These analyses show substantial interannual variability in PSC
areal coverage and also the well-known contrast between the Antarctic and
Arctic. The CALIPSO data also reveal seasonal and altitudinal variations in
Antarctic PSC composition, which are related to changes in HNO3 and
H2O observed by the Microwave Limb Sounder on the Aura satellite. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|