 |
| Titel |
An assessment of CALIOP polar stratospheric cloud composition classification |
| VerfasserIn |
M. C. Pitts, L. R. Poole, A. Lambert, L. W. Thomason |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 6 ; Nr. 13, no. 6 (2013-03-15), S.2975-2988 |
| Datensatznummer |
250018513
|
| Publikation (Nr.) |
 copernicus.org/acp-13-2975-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| This study assesses the robustness of the CALIOP (Cloud-Aerosol Lidar with
Orthogonal Polarization) polar stratospheric cloud (PSC) composition
classification algorithm – which is based solely on the spaceborne lidar
data – through the use of nearly coincident gas-phase HNO3 and H2O
data from the Microwave Limb Sounder (MLS) on Aura and Goddard Earth
Observing System Model, Version 5 (GEOS-5) temperature analyses. Following
the approach of Lambert et al. (2012), we compared the observed
temperature-dependent HNO3 uptake by PSCs in the various CALIOP
composition classes with modeled uptake for supercooled ternary solutions
(STS) and equilibrium nitric acid trihydrate (NAT). We examined the CALIOP
PSC data record from both polar regions over the period from 2006 through
2011 and over a range of potential temperature levels spanning the 15–30 km
altitude range. We found that most PSCs identified as STS exhibit gas phase
uptake of HNO3 consistent with theory, but with a small temperature
bias, similar to Lambert et al. (2012). Ice PSC classification is also
robust in the CALIOP optical data, with the mode in the ice observations
occurring about 0.5 K below the frost point. We found that CALIOP PSCs
identified as NAT mixtures exhibit two distinct preferred modes which
reflect the fact that the growth of NAT particles is kinetically limited.
One mode is significantly out of thermodynamic equilibrium with respect to
NAT due to short exposure times to temperatures below the NAT existence
temperature, TNAT, with HNO3 uptake dominated by the more numerous
liquid droplets. The other NAT mixture mode is much closer to NAT
thermodynamic equilibrium, indicating that the particles have been exposed
to temperatures below TNAT for extended periods of time. With a few
notable exceptions, PSCs in the various composition classes conform well to
their expected temperature existence regimes. We have a good understanding
of the cause of the minor misclassifications that do occur and will
investigate means to correct these deficiencies in our next generation
algorithm. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|