Microwave measurements of variations in night mesospheric ozone over Moscow

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.

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