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.
Continuous observations of the ozone layer and key constituents of ozone destruction are of primary importance for objective evaluation and forecasting the regional and global ozone layer depletion. Measurements of trace gas contents in the atmosphere require the use of highly sensitive and precise techniques and instruments. Millimeter-wave heterodyne spectroscopy is successfully used for ground based measuring of the atmospheric ozone at altitudes from about 15 to 80 km. Main features of the advanced system, based on a heterodyne receiver for the 142.2 GHz ozone spectral line measurements and 500-MHz acousto-optical spectrometer (AOS) are described. Key parts of the radiometer front-end, including input optics, low-noise Schottky diode mixer, and AOS are considered, as well as structure and performance of the data acquisition system. The characteristics and capabilities of this setup have been studied. Some performance characteristics of the acousto-optical spectrometer for the millimeter-wave radiometer are discussed. The main attention is given to the long-term stability of the AOS's parameters. Long-term amplitude stability estimations are based on the Allan variance method. Some initial results of ozone observations are presented.
MM-wave heterodyne spectroscopy is successfully used for measuring of the atmospheric ozone at altitudes from about 15 to 80 km. Remote sensing of trace gases, including ozone at MM waves has a number of obvious advantages. The required performance of a ground-based instrument for ozone observations at wavelength of 2 mm has bene determined using results of computer simulations. Main features of the Lebedev Physics Institute heterodyne radio spectrometer for 142.2 GHz ozone spectral line measurements are described, and key parts of the spectrometer receiver, such as input optics and low- noise Schottky diode mixer, are considered in greater detail. The receiver and the mixer have been tested throughout the 22- mm band at both room and liquid nitrogen temperatures and main results of the tests are presented. Blackbody cold loads have been used in the calibration/observation procedure, with special attention paid to accurately measuring their brightness temperatures. Some results of ozone observations for various atmosphere states are presented to demonstrate possibilities of ground-based MM-wave heterodyne spectroscopy.
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