Remote sensing of the atmospheric ozone at millimeter waves

Ground-based remote sensing of atmospheric ozone at millimeter (MM) waves is necessary for continuous day-and-night monitoring of the ozone layer. A valuable feature of the method and its advantage over observations at shorter wavelengths is low dependence on weather conditions because of the small effects of aerosols and clouds on the propagation of MM waves in the atmosphere. A low-noise heterodyne MM-wave radio spectrometer was built at the P.N. Lebedev Physical Institute (LPI) for ground-based measurements of the atmospheric ozone spectral line of 142.175 GHz (central frequency). High sensitivity and frequency resolution of the spectrometer allow to get accurate pressure-broadened ozone spectra which are used for the solution the inverse problem-retrieval the vertical ozone distribution (VOD) in the atmosphere. Regular ground-based ozone measurements have been carried out at the LPI since 1987 to study various processes and changes in the Earth's ozonosphere. The VOD for altitudes from about 15-20 to 75 km is retrieved from the spectra measured. The upper boundary of the altitude range is essentially higher than for balloons and ozone sondes and ground-based optical spectrometers and lidars. The LPI MM-wave spectrometer was incorporated into a ground-based network for ozone measurements during the international campaigns DYANA (1989-90), CRISTA/MAHRSI (1994), and CRISTA/MAHRSI-2 (1997).