The infrared remote sensing of peroxyacetyl nitrate in the upper troposphere
In this thesis, atmospheric limb-emission spectra measured by two Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instruments, the MIPAS balloon-borne version 2 (MIPAS-B2) and MIPAS on Envisat (MIPAS-E), have been used to successfully detect PAN in the UT by virtue of its characteristic infrared spectral signature for the first time.;This is achieved using new infrared laboratory reference cross-sections for PAN also obtained in this thesis. This spectral reference dataset represents improved room temperature cross-sections (<4% uncertainty at the 95% confidence level) for PAN in the spectral range 550-2200 cm -1 and the measurement of low temperature (down to 250 K) and nitrogen broadened (up to 300 mb) cross-sections appropriate to the UT for the first time.;Analysis of spectra measured by the MIPAS-B2 instrument over the Mediterranean Sea region in April 1998 and May 1999 has yielded PAN concentrations as high as 350 parts per trillion by volume (pptv) in the UT using an iterative spectral fitting and residual analysis method developed in this thesis.;The detection of PAN was also achieved using this method for spectra measured by the MIPAS-E instrument during April 2003 for the Mediterranean Sea and East China Sea regions. Back trajectories of airmasses observed by MIPAS-E indicate that very high PAN concentrations (up to 668 pptv) detected over the East China Seas may be indicative of pollution outflow from Asia. Limits of detection for PAN in the UT are estimated to be as low as 40 pptv.