Ice supersaturation in the tropopause region over Lindenberg, Germany

The occurrence of ice-supersaturation layers (in either clear air or in cirrus) over the Meteorological Observatory Lindenberg is investigated for the period February 2000 to April 2001 by means of the humidity, temperature, and pressure reports obtained from the Lindenberg corrected RS80A routine radiosonde. The RS80A routine sonde data are corrected on the basis of weekly comparison ascents with Lindenberg research radiosonde humidity data. This research sonde applies the Lindenberg measuring and evaluation technique of standardized frequencies. We study the frequency of occurrence of ice supersaturation in the tropopause region over Lindenberg, the vertical distribution of ice-supersaturation layers in the upper troposphere and lowermost stratosphere, their situation relative to the tropopause, their vertical dimensions, their temperatures and the statistical distribution of relative humidities. The mean frequency of occurrence of ice-supersaturation layers is about 28%. Most of them occur within a broad layer extending 200 hPa down from the tropopause. Most events occur in cold air with temperature below -40°C. Their vertical extensions can be fitted by a pair of Weibull distributions with mean 560 ± 610 m. The results are compared with findings from the MOZAIC project, from the SAGE II satellite instrument, and with various results from Lidar measurements.

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