Data of night-time ground-based measurements of the atmospheric ozone spectral line 142.175 GHz over Moscow were used for detection of variations in the ozone mixing ratio (OMR) at altitudes of the secondary (near 90 km) and tertiary (near 65 km) night maxima in the OMR profile. The ozone spectra were recorded by low-noise microwave spectrometer MOS-4 with frequency resolution of 0.1 MHz and time resolution of 110 or 90 s, not quite evenly spaced in time. The spectra were averaged over groups of 6…60 ones. The OMR values at altitudes of 90 and 65 km were determined by the improved least-squares method applied to differences of brightness temperatures within ±0.5 MHz frequency offsets from the ozone line centre. Then special algorithm based on the Lomb periodograms with sliding data window was used to determine spectral power and frequencies of the ozone variations. Estimates of the OMR errors depending on the instrumental noise and number of averaged spectra were obtained by computer simulations and used to calculate detection thresholds of the Lomb algorithm. Wave-type variations in the OMR values with periods of 3…5 h were detected with probability of 85-90% at altitude of 90 km and 95-97% at 65 km. Spans of the variations were up to 9 ppm at 90 km and up to 2 ppm at 65 km. The paper presents descriptions of the instrumentation, observation procedure, data processing methods, and some results of the data analysis.
Results of regular ground-based millimeter-wave (MM-wave) measurements of vertical ozone distribution (VOD)
in the stratosphere and mesosphere over Moscow region for the last years are presented. The observations of the
142.175 GHz ozone line were done using low-noise heterodyne spectrometer. Tikhonov method was used for retrieval
the ozone mixing ratio profiles from the experimental spectra. Descriptions of both the retrieval algorithm and the
spectrometer are given. As seasonal changes in ozone as more short-term ozone variations with time scales from several
days to several weeks were recorded. It was found that the most noticeable changes in the ozone layer occurred in cold
seasons. Correlations between ozone content and other parameters of the atmosphere were established for different
altitudes. It was shown that the VOD over Moscow is strongly influenced by large-scale atmospheric dynamics.
Considerable deformations of the stratospheric ozone profiles were detected in winter months, when both decreased
ozone content at altitudes of 25-45 km and local minimum near 30 km were observed many times. Appearance of the
secondary (in the lower thermosphere around 90 km) and tertiary (in the mesosphere at altitudes of 55-75 km) maxima in
the ozone profiles in night hours, and strong variations in the night ozone at the altitudes were measured. A comparison
of the ground-based MM-wave data with results of satellite measurements by EOS MLS instrument has shown good
coincidence of the ozone profiles obtained from the ground level and from space.
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