ALOMAR

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ALOMAR observatory building (2008)

The ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) is a geophysical observatory on the 379 m high Ramnan mountain on the northern Norwegian island of Andøya north of the Arctic Circle .

The local operator of the research station is the Andøya Rakettskytefelt rocket base (Andøya Space Center) . The scientific instruments are operated by the Leibniz Institute for Atmospheric Physics at the University of Rostock in cooperation with the Service d'aéronomi du Center national de la recherche scientifique in Guyancourt ( France ). The ALOMAR research station was founded in 1994 by the first director of the Leibniz Institute for Atmospheric Physics Ulf von Zahn with the aim of researching the polar mean atmosphere.

With its instruments, the ALOMAR represents a fully equipped atmosphere laboratory. Four lidar systems and several passive remote sensing systems are installed in the observatory . The core of the observatory is the RMR lidar, which bears its name after the scattering mechanisms used, Rayleigh , Mie and Raman scattering . The observatory has a double lidar. It consists of two power lasers with two Cassegrain telescopes for reception, the primary mirrors of which have a diameter of 1.8 m, as well as an optical bench for the detection of the light scattered back from the atmosphere. The two pulsed Nd: YAG lasers of the RMR lidar simultaneously emit light at a wavelength of 1064 nm ( infrared radiation ) and its harmonics at 532 nm (visible green part of the light spectrum) and 355 nm (border between the violet part and the ultraviolet part Light ). They are operated alternately from pulse to pulse with a pulse repetition frequency of 30 Hertz. With this lidar, continuous measurements in an altitude range of up to 100 km have been possible since 1995.

The ALOMAR research station includes several radar systems, which are located about 2.5 km north-north-east of the observatory building. This is the MST radar (Mesospheric-Stratospheric-Tropospheric Radar) MAARSY (Middle Atmosphere Alomar Radar System) working in the lower VHF range , which replaced the smaller ALWIN radar (Alomar Wind Radar) located next to it from 2010 . Parts of its antenna field are still used as passive receivers under the name ALWIN64.

With the help of the radar, the echo signals of the mesospheric ice particles typical in the polar region in summer are received from a height of more than 80 km. At this altitude, the atmosphere is extremely thin, so that only a few such ice particles form and form thin, glowing night clouds. These ice particles are very small, which means that the radar must be particularly sensitive. By electronically tilting the antenna diagram , the horizontal structure of these polar mesospheric summer echoes can be recorded. This allows horizontal wind speeds and turbulence in the mesosphere to be examined three-dimensionally. The results of the investigations with radar and lidar play an important role for climate models and for understanding climate change.

Individual evidence

  1. ↑ a b c Maike Pfalz: Atmospheric Arctic . In: Physik-Journal . tape 16 , no. 7 , July 2017, p. 24–28 ( pro-physik.de [accessed February 4, 2021]).
  2. ↑ The ALOMAR Rayleigh / Mie / Raman lidar. Retrieved February 6, 2021 .
  3. ↑ Christian Wolff: MAARSY. In: Radar Tutorial. November 1998, accessed February 4, 2021 .
  4. ↑ T. Renkwitz, W. Singer, R. Latteck, M. Rapp: Multi beam observations of cosmic radio noise using a VHF radar with beam forming by a Butler matrix . In: Advances in Radio Science . tape 9 . Copernicus GmbH, 2011, p. 349–357 , doi : 10.5194 / ars-9-349-2011 ( psu.edu [PDF; accessed February 4, 2021]).

Coordinates: 69 ° 16 ′ 42 "  N , 16 ° 0 ′ 33.2"  E