Noctilucent clouds and the mesospheric water vapour: the past decade
The topic of this paper is the sensitivity of the brightness of noctilucent clouds (NLC) on the ambient water vapour mixing ratio f(H<sub>2</sub>O). Firstly, we use state-of-the-art models of NLC layer formation to predict NLC brightness changes in response to changes in the 80km mixing...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2004-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/4/2449/2004/acp-4-2449-2004.pdf |
| _version_ | 1817993332389838848 |
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| author | U. von Zahn G. Baumgarten U. Berger J. Fiedler P. Hartogh |
| author_facet | U. von Zahn G. Baumgarten U. Berger J. Fiedler P. Hartogh |
| author_sort | U. von Zahn |
| collection | DOAJ |
| description | The topic of this paper is the sensitivity of the brightness of noctilucent clouds (NLC) on the ambient water vapour mixing ratio f(H<sub>2</sub>O). Firstly, we use state-of-the-art models of NLC layer formation to predict NLC brightness changes in response to changes in the 80km mixing ratio f(H<sub>2</sub>O) for the two cases of ground-based 532nm lidar observations at 69° N and for hemispheric satellite SBUV observations at 252nm wavelength. In this study, we include a re-evaluation of the sensitivity of NLC brightness to changes in solar Lyman α flux. Secondly, we review observations of episodic changes in f(H<sub>2</sub>O) and those in NLC brightness, the former being available since 1992, the latter since 1979. To this review, we add a new series of observations of f(H<sub>2</sub>O), performed in the Arctic summer at the ALOMAR observatory. The episodic change exhibited by the Arctic summer means of f(H<sub>2</sub>O) turns out to be quite different from all those derived from annual means of f(H<sub>2</sub>O). The latter indicate that since 1996 a significant reduction of annually averaged upper mesospheric water vapour has occurred at low, mid, and high latitudes. These decreases of f(H<sub>2</sub>O) have been observed over the same time period in which a slow increase of SBUV NLC albedo has occurred. From this scenario and additional arguments we conclude that the cause for the observed long-term increase in NLC albedo remains to be identified. We close with comments on the very different character of decadal variations in NLC brightness and occurrence rate. |
| first_indexed | 2024-04-14T01:38:29Z |
| format | Article |
| id | doaj.art-5f8e86a7477f451aa7f385aec9dbea46 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-14T01:38:29Z |
| publishDate | 2004-01-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-5f8e86a7477f451aa7f385aec9dbea462022-12-22T02:19:52ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242004-01-01411/1224492464Noctilucent clouds and the mesospheric water vapour: the past decadeU. von ZahnG. BaumgartenU. BergerJ. FiedlerP. HartoghThe topic of this paper is the sensitivity of the brightness of noctilucent clouds (NLC) on the ambient water vapour mixing ratio f(H<sub>2</sub>O). Firstly, we use state-of-the-art models of NLC layer formation to predict NLC brightness changes in response to changes in the 80km mixing ratio f(H<sub>2</sub>O) for the two cases of ground-based 532nm lidar observations at 69° N and for hemispheric satellite SBUV observations at 252nm wavelength. In this study, we include a re-evaluation of the sensitivity of NLC brightness to changes in solar Lyman α flux. Secondly, we review observations of episodic changes in f(H<sub>2</sub>O) and those in NLC brightness, the former being available since 1992, the latter since 1979. To this review, we add a new series of observations of f(H<sub>2</sub>O), performed in the Arctic summer at the ALOMAR observatory. The episodic change exhibited by the Arctic summer means of f(H<sub>2</sub>O) turns out to be quite different from all those derived from annual means of f(H<sub>2</sub>O). The latter indicate that since 1996 a significant reduction of annually averaged upper mesospheric water vapour has occurred at low, mid, and high latitudes. These decreases of f(H<sub>2</sub>O) have been observed over the same time period in which a slow increase of SBUV NLC albedo has occurred. From this scenario and additional arguments we conclude that the cause for the observed long-term increase in NLC albedo remains to be identified. We close with comments on the very different character of decadal variations in NLC brightness and occurrence rate.http://www.atmos-chem-phys.net/4/2449/2004/acp-4-2449-2004.pdf |
| spellingShingle | U. von Zahn G. Baumgarten U. Berger J. Fiedler P. Hartogh Noctilucent clouds and the mesospheric water vapour: the past decade Atmospheric Chemistry and Physics |
| title | Noctilucent clouds and the mesospheric water vapour: the past decade |
| title_full | Noctilucent clouds and the mesospheric water vapour: the past decade |
| title_fullStr | Noctilucent clouds and the mesospheric water vapour: the past decade |
| title_full_unstemmed | Noctilucent clouds and the mesospheric water vapour: the past decade |
| title_short | Noctilucent clouds and the mesospheric water vapour: the past decade |
| title_sort | noctilucent clouds and the mesospheric water vapour the past decade |
| url | http://www.atmos-chem-phys.net/4/2449/2004/acp-4-2449-2004.pdf |
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