Retrieval of noise-limited minor atmospheric constituents from satellite emission measurements and determination of atmospheric trends

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb Fourier transform spectrometer that operated onboard the polar-orbiting ESA ENVIronmental SATellite from July 2002 to April 2012. MIPAS measured the atmospheric limb emission in the middle/upper atmosphere in the spectral range from 4.15 to 14.6 μm. The MIPAS instrument was designed to improve the knowledge of the distribution of some key chemical components and the dynamics of the middle atmosphere. The main target of this PhD thesis is the retrieval and the study of minor constituents of the middle atmosphere using MIPAS measurements. These molecules give a minor contribution to the MIPAS spectra but their retrieval is fundamental to improve the general knowledge of the chemistry of the middle atmosphere. In the first part of this PhD project, we focused on the retrieval of carbonyl chloride (COCl2) and on the study of its distribution in the UTLS region. COCl2 is a gas used in the insecticides, pharmaceuticals and herbicides preparation. Due to its high toxicity, its usage has been reduced over the years. COCl2 has been retrieved for the first time using MIPAS measurements. The main features and the seasonality of its distribution have been studied and compared with ACE-FTS measurements. In the second part, we studied the carbon tetrachloride (CCl4) lifetime, its global distribution and its seasonality in the UTLS region using the ESA official Level 2 Version 7 products. CCl4 is a strong ozone-depleting substance, banned by the Montreal protocol starting from 1996. MIPAS CCl4 measurements have been compared with independent measurements from ACE-FTS, MIPAS-Balloon and data from the EMAC model. CCl4 trends as a function of latitude and altitude have been evaluated and compared with other satellite trend estimates and other surface global network measurements.