G. Hansen

Norwegian Institute for Air Research

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U. von Zahn

Leibniz Institute of Atmospheric Physics at the Rostock University

U.‐P. Hoppe

UiT The Arctic University of Norway

Kerstin Stebel

Norwegian Institute for Air Research

P. Pollari

University of Oulu

Esa Turunen

University of Oulu

M. Gausa

Andøya Space Center

Kåre Edvardsen

Centre for Arctic Gas Hydrate, Environment and Climate

Peter von der Gathen

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

G. von Cossart

Leibniz Institute of Atmospheric Physics at the Rostock University

Rigel Kivi

Finnish Meteorological Institute

Cooperative Institutions

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

University of Bonn

Norwegian Institute for Air Research

Kjeller Innovasjon (Norway)

Leibniz Institute of Atmospheric Physics at the Rostock University

University of Rostock

Centre for Arctic Gas Hydrate, Environment and Climate

UiT The Arctic University of Norway

University of Bremen

Danish Meteorological Institute

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First detection of a noctilucent cloud by lidar

Geophysical Research Letters (1989)

G. Hansen Marcus Serwazi U. von Zahn

During the night of August 5/6, 1989 for the first time a noctilucent cloud (NLC) was detected and measured by a lidar instrument. The observations were made with our ground‐based narrow‐band Na lidar located at Andenes, Norway (69°N, 16°E geographic coordinates). In wavelength the lidar was operated both at the Na D 2 resonance line of 589 nm as well as 5 Doppler widths shifted away. The altitude resolution was 200 m. The NLC developed at about 22:20 UT, reached its maximum backscatter cross section at 23:05 UT and became unobservable at around 00:10 UT. During this period the NLC exhibited the following properties: (a) its altitude ranged between 83.4 and 82.2 km; (b) its full width at half maximum ranged between 1.4 and 0.3 km; (c) the ratio of measured backscatter intensity from the NLC to the calculated Rayleigh signal from 82.6 km reached 450; (d) its volume backscatter cross section maximized at 6.5·10 −9 m −1 sr −1 .

Backscatter (email)

10.1029/gl016i012p01445

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Lidar algorithm comparison of PSC measurements at Ny-Ålesund, Sodankylae and ALOMAR

Kerstin Stebel Marion Müller G. Hansen Roland Neuber Rigel Kivi

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Forced release of sodium from upper atmospheric dust particles

Geophysical Research Letters (1987)

U. von Zahn Peter von der Gathen G. Hansen

The almost explosive growth of narrow sodium layers at altitudes near 95 km was observed by ground‐based LIDAR located at 69°N, 16°E. Starting from typical conditions at these altitudes (sodium density approximately 1 to 2× 10³ cm −3 ) the density is observed to increase by large factors within a few minutes in a narrow layer, the half height of which is typically 1 km only. One of the more spectacular cases involved an increase by a factor 25 within 5 min and a layer width of 0.8 km (full width at half maximum). We propose that the sodium forming these sudden layers is released from upper atmospheric dust by energetic auroral particles. Prior to the auroral bombardment the dust particles were concentrated into a narrow layer by appropriate meteorological processes. Our observations thus imply that considerable amounts of sodium are stored on the surface of upper atmospheric dust.

Surface layer

10.1029/gl014i001p00076

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Ozone Profiles from the Edge of the Polar Vortex - Winter 2003

EGS - AGU - EUG Joint Assembly (2003)

Trude Storelvmo M. Gausa Kerstin Stebel G. Hansen Kåre Edvardsen

Ozone Depletion

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Comparison of observed and calculated incoherent scatter spectra from the D region

Radio Science (1991)

G. Hansen U.‐P. Hoppe Esa Turunen P. Pollari

During August 1989, extended twilight and nighttime measurements with the European incoherent scatter (EISCAT) UHF radar were performed under PCA conditions. This provided an excellent data quality in the altitude region of 70 to 90 km throughout the three nights of August 12 to 15, 1989. A sophisticated control program allowed the measurement of the spectral width in the altitude region mentioned. In general, the measured spectral width deviates significantly from model values based on temperatures measured simultaneously by Na lidar combined with CIRA 88 temperature and density values. The observed spectra are up to 2 or 3 times narrower. In our observations the deviation tends to increase with increasing altitude. We also find that earlier spectral width measurements published by other workers are often narrower than current D region theory predicts. The possible reasons for this phenomenon are discussed.

Spectral width

10.1029/91rs01430

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Observations of the sodium layer at high latitudes in summer

Nature (1988)

U. von Zahn G. Hansen H. Kurzawa

Photometer

Middle latitudes

10.1038/331594a0

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Noctilucent clouds: One- and two-color lidar observations

Geophysical Research Letters (1997)

G. von Cossart J. Fiedler U. von Zahn G. Hansen U.‐P. Hoppe

From early July until mid‐August 1995 we observed six noctilucent clouds (NLC) above the ALOMAR observatory in Northern Norway (69°N, 16°E) with ground based lidar. The NLC layers had maximum backscatter ratios between 17 and 190 at 532 nm, their mean altitude was 83.0 km. The latest of these events (August 12/13, 1995) was observed by two lidars, both, the Rayleigh‐ and the ozone lidar, located in the ALOMAR observatory, on wavelengths of 532 nm and 308 nm, respectively. During the period of common‐volume observations from 23:55 UT until 01:30 UT, maximum averaged backscatter ratios of 56 and 28 were measured at 532 and 308 nm, respectively. If we assume spherical particles and a lognormal particle size distribution of width s, standard Mie theory yields median radii r m of the NLC particles between 16 nm and 44 nm with number densities between 2780 cm −3 and 160 cm −3 for assumed values of s between 1.6 and 1.2, respectively.

Backscatter (email)

10.1029/97gl01575

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Reconstruction of Ozone Profile and Column at Andøya in the Winter 1997/98

ESASP (1999)

Yvan Orsolini G. Hansen G. L. Manney N. J. Livesey U.‐P. Hoppe

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Simultaneous observations of noctilucent clouds and mesopause temperatures by lidar

Journal of Geophysical Research Atmospheres (1994)

G. Hansen U. von Zahn

During the night of August 5–6, 1989, geometric and optical properties of a noctilucent cloud (NLC) as well as the thermal structure of the atmosphere above the cloud were measured by ground‐based lidar. The data were collected at Andenes, Norway (69°N, 16°E). The cloud was observed from 2220 UT until 0010 UT, during which time its mean altitude was 82.6 km. Temperatures were measured from 2129 UT until 0017 UT in the altitude range of 86 to 94 km. A persistent temperature minimum was located in the 87‐ to 89‐km altitude region with temperatures dropping from close to 140 K at the beginning of the NLC observation to around 130 K after midnight. In a 2‐km‐wide layer below this minimum the temperature was persistently too high to provide supersaturation of water assuming realistic water concentrations. Comparison with other temperature measurements in the first half of August 1989 shows that the thermal conditions at the mesopause on August 5–6, 1989, were not especially favorable for the formation of NLCs, while on other occasions with lower mesopause temperatures no NLCs were observed. We conclude that the occurrence of NLCs only limitedly depends on the local thermal conditions at the display height and above. Instead, the conditions along the whole NLC particle trajectory have to be taken into account. This implies that horizontal and vertical advection are important factors controlling the occurrence of NLC displays in late summer at this latitude.

Mesopause

10.1029/94jd01524

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D-region incoherent scatter spectra: Discrepancies between observations and current theory

U.‐P. Hoppe G. Hansen Esa Turunen P. Pollari

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