Spectroscopic Study of the Absorption Properties of Ozone and Methane for use in the Remote Sensing Applications

Abstract

Monitoring of the atmospheric composition of the Earth is essential for studying the processes occurring in different layers of the atmosphere and, consequently, for air quality control and the climate change prediction. The most important conclusions are based on the data from the long-term global observations. Nowadays this data is coming from both space- or airborne instruments and ground based monitoring networks. The ozone (O3) and the methane (CH4) are among the most important trace gases. They play crucial role in the physical and chemical processes in the atmosphere, like formation of the protective stratospheric ozone layer or contribution to the greenhouse effect by absorption of the solar radiation (by both ozone and methane) or radiation re-emitted by the Earth s surface. Another important factor is that both ozone and methane concentration and distribution changes serve as the important markers of the anthropogenic influence on the environment. The atmospheric composition is derived after processing the spectra acquired by the satellite-borne instruments. Most methods utilize the fitting of the observed and synthetic spectra. Modelled spectra are produced based on the preliminary assumptions of approximate concentrations, temperatures and altitude distribution of the trace gases. These methods require a precise knowledge of the electromagnetic radiation absorption characteristics of the different atmospheric gases in a wide spectral range, as well as the temperature and pressure dependences of these parameters. The uncertainties in these tabulated spectral data lead to the uncertainties in the resulting retrieved concentrations and distribution profiles of atmospheric gases. Most of the modern instruments operate in the ultraviolet, visible and infrared parts of the spectrum between 250 nm and 1000 nm for ozone observations. For methane detection, infrared regions of the spectrum around 1,6 or 2,4 micron are mostly used. Despite the fact that different research groups have been analysing the absorption spectra of both ozone and methane with a lot of scrutiny for decades, there still is a room for improvement of the quality of the data. Consequently, the new detailed spectroscopic data would allow to further increase the quality of the atmospheric observations. Demand for an updated and improved (in terms of uncertainties and parameterization capabilities) spectroscopic data for ozone and methane from the remote sensing community was a major motivating factor for this study. This work is dedicated to the acquisition of the new high-quality broadband absorption spectra of ozone and methane, corresponding data analysis and the methods of achieving these goals.