Ground-based microwave monitoring of the atmospheric ozone

Investigations of the atmospheric ozone and processes resulting in anomalous changes in the ozone layer (ozone depletion at polar and middle latitudes, and ozone "holes") have become one of the most important problems [1]. Major tasks are investigations of changes in the vertical distribution of ozone in stratosphere and mesosphere under influence of natural processes, industrial impacts, and changes in thermal state of the atmosphere. Ground-based remote sensing of the ozone layer at MM-waves has a number of essential advantages over the traditional optical methods. MM-wave emission less suffers from absorption and scattering by aerosols and hydrometeors in comparison with shorter wavelength bands, so MM-wave observations are possible under various weather conditions (fog, clouds) hindering to optical sounding. Furthermore, MM-wave measurements don\´t depend on solar illumination, making possible day-and-night observations. The microwave technique of remote sensing was successfully used at the LPI (P.N. Lebedev Physical Institute of the Russian Academy of Sciences) for the ozone observations [2, 3]. The measurements are carried out at frequencies of the ozone line centered at 142.175 GHz, located in 2-mm atmospheric transparence window. The LPI spectrometer has high frequency resolution and low noise, so the contour of the pressurebroadened rotational spectral line of ozone molecules is measured with high accuracy. This is very important for successful solution of inverse problem, i.e. the retrieval of the ozone vertical distribution in the stratosphere and mesosphere. Remote sensing of the atmospheric ozone at frequencies of this spectral line of ozone molecules allows to measure vertical distribution of ozone molecules in middle atmosphere (see Figs. 1, 2).