First observations of noctilucent clouds by lidar at Svalbard, 78°N J. Höffner, C. Fricke-Begemann, and F.-J. Lübken Leibniz-Institut für Atmosphärenphysik, Kühlungsborn, Germany
Abstract. In summer 2001 a potassium lidar was installed near
Longyearbyen (78° N) on the north polar island of Spitsbergen which is part of the archipelago Svalbard. At the same place a series of meteorological
rockets ("falling spheres", FS) were launched which gave temperatures from the lower
thermosphere to the stratosphere. The potassium lidar is capable of detecting noctilucent clouds (NLCs) and of measuring temperatures in the lower
thermosphere, both under daylight conditions. In this paper we give an overview on the NLC measurements (the first
at this latitude) and compare the results with temperatures from meteorological rockets which have been published recently
(Lübken and Mülleman, 2003) NLCs were observed from 12 June (the first day of operation) until 12 August when
a period of bad weather started. When the lidar was switched on again on 26 August, no NLC was observed. The mean occurrence frequency
in the period 12 June -- 12 August ("lidar NLC period") is 77%. The mean of all individual NLC peak altitudes
is 83.6 km (variability: 1.1 km). The mean peak NLC altitude does not show a significant
variation with season. The average top and bottom altitude of the NLC layer is 85.1 and
82.5 km, respectively, with a variability of ~1.2 km. The mean of the maximum volume backscatter coefficient
at our wavelength of 770 nm is 3.9 x 10-10/m/sr with a large variability of
±3.8 x 10-10/m/sr. Comparison of NLC characteristics with measurements at ALOMAR
(69° N) shows that the peak altitude and the maximum volume backscatter coefficient are similar at both locations but NLCs
occur more frequently at higher latitudes.
Simultaneous temperature and NLC measurements are available for 3 flights and
show that the NLC layer occurs in the lower part of the height range with super-saturation. The NLC peak occurs over a large range of degree of saturation
(S) whereas most models predict the peak at S = 1. This demonstrates that steady-state
considerations may not be applicable when relating individual NLC properties
to background conditions. On the other hand, the mean variation of the NLC appearance with height and season is in agreement with the climatological variation
of super-saturation derived from the FS temperature measurements.
Citation: Höffner, J., Fricke-Begemann, C., and Lübken, F.-J.: First observations of noctilucent clouds by lidar at Svalbard, 78°N, Atmos. Chem. Phys., 3, 1101-1111, doi:10.5194/acp-3-1101-2003, 2003.