First observation of one noctilucent cloud by a twin lidar in two different directions
In the early morning hours of 14 July 1999, a noctilucent cloud (NLC) was observed simultaneously by the two branches of a twin lidar system located at the ALOMAR observatory in northern Norway (69° N). The telescopes of the two lidars were pointing vertical (L<font face="Symbol"...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2002-11-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/20/1863/2002/angeo-20-1863-2002.pdf |
| _version_ | 1819072878977482752 |
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| author | G. Baumgarten G. Baumgarten F.-J. Lübken K. H. Fricke |
| author_facet | G. Baumgarten G. Baumgarten F.-J. Lübken K. H. Fricke |
| author_sort | G. Baumgarten |
| collection | DOAJ |
| description | In the early morning
hours of 14 July 1999, a noctilucent cloud (NLC) was observed simultaneously by
the two branches of a twin lidar system located at the ALOMAR observatory in
northern Norway (69° N). The telescopes of the two lidars were pointing
vertical (L<font face="Symbol" ><sub>^</sub></font>) and off the zenith
by 30° (L<sub>30°</sub>). The two lidars detected an enhancement in the
altitude profile of backscattered light (relative to the molecular background)
for more than 5 h, starting approximately at 01:00 UT. These measurements
constitute the detection of one NLC by two lidars under different directions
and allow for a detailed study of the morphology of the NLC layer. A
cross-correlation analysis of the NLC signals demonstrates that the main
structures seen by both lidars are practically identical. This implies that a
temporal evolution of the microphysics within the NLC during its drift from one
lidar beam to the other is negligible. From the time delay of the NLC
structures, a drift velocity of 55–65 m/s is derived which agrees nicely with
radar wind measurements. During the observation period, the mean NLC altitude
decreases by ~0.5 km/h (=14 cm/s) at both observation volumes. Further-more,
the NLC is consistently observed approximately 500 m lower in altitude at L<sub>30°</sub>
compared to L<font face="Symbol" ><sub>^</sub></font>. Supplementing
these data by observations from rocket-borne and ground-based instruments, we
show that the general downward progression of the NLC layer through the night,
as seen by both lidars, is caused by a combination of particle sedimentation by
4–5 cm/s and a downward directed vertical wind by 9–10 cm/s, whereas a tilt
of the layer in drift direction can be excluded.<br><br><b>Key words. </b>Atmospheric composition and structure
(cloud physics and chemistry; aerosols and particles) Meteorology and
atmospheric dynamics (middle atmosphere dynamics) |
| first_indexed | 2024-12-21T17:44:44Z |
| format | Article |
| id | doaj.art-81ae799641744379871717d0c61d9c4b |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-21T17:44:44Z |
| publishDate | 2002-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-81ae799641744379871717d0c61d9c4b2022-12-21T18:55:32ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762002-11-01201863186810.5194/angeo-20-1863-2002First observation of one noctilucent cloud by a twin lidar in two different directionsG. Baumgarten0G. Baumgarten1F.-J. Lübken2K. H. Fricke3Correspondence to: F.-J. Lübken (luebken@iap-kborn.de)Leibniz-Institut für Atmosphärenphysik, Kühlungsborn, GermanyLeibniz-Institut für Atmosphärenphysik, Kühlungsborn, GermanyPhysikalisches Institut der Universität Bonn, Bonn, GermanyIn the early morning hours of 14 July 1999, a noctilucent cloud (NLC) was observed simultaneously by the two branches of a twin lidar system located at the ALOMAR observatory in northern Norway (69° N). The telescopes of the two lidars were pointing vertical (L<font face="Symbol" ><sub>^</sub></font>) and off the zenith by 30° (L<sub>30°</sub>). The two lidars detected an enhancement in the altitude profile of backscattered light (relative to the molecular background) for more than 5 h, starting approximately at 01:00 UT. These measurements constitute the detection of one NLC by two lidars under different directions and allow for a detailed study of the morphology of the NLC layer. A cross-correlation analysis of the NLC signals demonstrates that the main structures seen by both lidars are practically identical. This implies that a temporal evolution of the microphysics within the NLC during its drift from one lidar beam to the other is negligible. From the time delay of the NLC structures, a drift velocity of 55–65 m/s is derived which agrees nicely with radar wind measurements. During the observation period, the mean NLC altitude decreases by ~0.5 km/h (=14 cm/s) at both observation volumes. Further-more, the NLC is consistently observed approximately 500 m lower in altitude at L<sub>30°</sub> compared to L<font face="Symbol" ><sub>^</sub></font>. Supplementing these data by observations from rocket-borne and ground-based instruments, we show that the general downward progression of the NLC layer through the night, as seen by both lidars, is caused by a combination of particle sedimentation by 4–5 cm/s and a downward directed vertical wind by 9–10 cm/s, whereas a tilt of the layer in drift direction can be excluded.<br><br><b>Key words. </b>Atmospheric composition and structure (cloud physics and chemistry; aerosols and particles) Meteorology and atmospheric dynamics (middle atmosphere dynamics)https://www.ann-geophys.net/20/1863/2002/angeo-20-1863-2002.pdf |
| spellingShingle | G. Baumgarten G. Baumgarten F.-J. Lübken K. H. Fricke First observation of one noctilucent cloud by a twin lidar in two different directions Annales Geophysicae |
| title | First observation of one noctilucent cloud by a twin lidar in two different directions |
| title_full | First observation of one noctilucent cloud by a twin lidar in two different directions |
| title_fullStr | First observation of one noctilucent cloud by a twin lidar in two different directions |
| title_full_unstemmed | First observation of one noctilucent cloud by a twin lidar in two different directions |
| title_short | First observation of one noctilucent cloud by a twin lidar in two different directions |
| title_sort | first observation of one noctilucent cloud by a twin lidar in two different directions |
| url | https://www.ann-geophys.net/20/1863/2002/angeo-20-1863-2002.pdf |
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