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| Titel |
Characteristics of aerosol and cloud particle size distributions in the tropical tropopause layer measured with optical particle counter and lidar |
| VerfasserIn |
S. Iwasaki, K. Maruyama, M. Hayashi, S.-Y. Ogino, H. Ishimoto, Y. Tachibana, A. Shimizu, I. Matsui, N. Sugimoto, K. Yamashita, K. Saga, K. Iwamoto, Y. Kamiakito, A. Chabangborn, B. Thana, M. Hashizume, T. Koike, T. Oki |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 7, no. 13 ; Nr. 7, no. 13 (2007-07-03), S.3507-3518 |
| Datensatznummer |
250005120
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| Publikation (Nr.) |
 copernicus.org/acp-7-3507-2007.pdf |
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| Zusammenfassung |
| An optical particle counter (OPC) is used in conjunction with lidar
measurements to examine the characteristics of the particle size
distribution in cirrus cloud in the tropical tropopause layer (TTL) over
Thailand where the TTL is defined as the height at which temperature is
lower than −75°C in this paper. Of 11 OPC launches, cirrus cloud was
detected at 10–15 km high on 7 occasions, cirrus was detected in the TTL in
6 cases, and simultaneous OPC and lidar measurements were made on two
occasions. Comparison of lidar and OPC measurements reveal that the cloud
heights of cirrus in the TTL varies by several hundred meters over distances
of tens kilometers; hence the height is not always horizontally uniform. The
mode radii of particles constituting the clouds are estimated by lidar and
OPC measurements to be less than approximately 10 μm. The regression
lines of the particle size distribution with and without cirrus cloud exhibit
similar features at equivalent radii of <0.8 μm. Enhancement in the
integrated number concentration at radii greater than 0.8 μm indicates
that liquid particles tend to be frozen at a radius of 0.8 μm, with
cirrus clouds above 10 km exhibiting similar features. On the other hand,
enhancement in the particle size distribution at radii greater than 0.9 μm and
a peak at around 0.8 μm in the ratio of the standard deviation
of count values to that of the Poisson distribution of the averaged count
values are common features of cirrus clouds in the TTL, where the ratio
shows the vertical homogeneity of the particle number. These typical
features suggest that the transition from liquid, sulfuric acid aerosol, to
ice is more observable in the TTL and the timing of freezing may vary with
height in the TTL. |
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