Some remarks to the development of upper atmosphere wind measurements at the Collm Geophysical Observatory

Wind Measurements at the Collm Geophysical Observatory

At the Collm Observatory (51.3N, 13E) of the Leipzig University since 1959 winds at mesopause heights (80 - 110 km altitude) are measured. The measurements base on the total reflection of radio waves in the lower nighttime ionosphere using commercial radio transmitters on three measuring paths (at present on 177, 225, and 270 kHz, additionally 261 kHz). Since 1959 the used frequencies were changed several times due to the requirements of the respective radio stations, but not for more than 10 kHz.
In the beginning the data evaluation was done manually. Until 1973 they were automated. Since September 1982 the reflection (reference) heights, measured on 177 kHz (until 31.1.1986: 179 kHz), are used to calculate monthly or half-monthly profiles and from this height-time cross-sections of the wind field parameters. The results are published in monthly reports and 120 original papers in the years 1960-96.

The regularly estimated parameters are:

half-hourly means of the horizontal wind (about 12-18 hours/day, depending from season; all three measuring paths, and the mean) and the reflection height
mean monthly or half - monthly wind profiles between about 85 and 105 km altitude
daily values of the horizontal prevailing wind and the semidiurnal tide at about 95 km altitude

The data are available on request.

The figure shows the number of evaluated half-hourly means on 5 measuring paths between 1963 and 1995. The frequencies 245 and 263 kHz were used as substitute for the 272 kHz path that was not available for 41 months in the years 1975 - 1978 as the result of transmitter reconstruction. Note the strong increase of measurements in the beginning of the 70s, which is due to the automated measurements since then.
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