Phosgene distribution derived from MIPAS ESA v8 data: intercomparisons and trends

Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measured the middle-infrared limb emission spectrum of atmosphere from 2002 to 2012 on board ENVISAT, a polar-orbiting satellite. Recently, European Space Agency (ESA) completed final reprocessing MIPAS measurements, using version 8 level 1 and 2 processors, which include more accurate models, processing strategies, auxiliary data. list retrieved gases has been extended, it now includes number new species with weak features in spectral range. trace carbonyl chloride (COCl2), also called phosgene. Due its toxicity, use reduced over years; however, is still used by chemical industries several applications. Besides direct injection troposphere, stratospheric phosgene mainly produced photolysis CCl4, molecule present because human activity. Since long lifetime, must be carefully monitored as involved ozone destruction cycles, especially winter polar regions. In this paper we exploit ESA data order discuss distribution, variability, trends middle lower stratosphere upper troposphere. zonal averages show that volume mixing ratio larger stratosphere, peak 40 pptv (parts per trillion volume) between 50 30 hPa at equatorial latitudes, while latitudes varies 10 25 pptv. A moderate seasonal variability observed regions, mostly 80 hPa. comparison MIPAS–ENVISAT COCl2 v8 profiles ones balloon ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) measurements highlights negative bias about pptv, mid-latitude Part attributed fact processor uses an updated spectroscopic database. For trend computation, fixed pressure grid interpolate profiles, and, each level, VMR (volume ratio) monthly are computed pre-defined 10∘ wide latitude bins. Then, latitudinal bin regression model fitted resulting time series derive atmospheric trends. We find different two hemispheres. analysis shows Northern Hemisphere characterized −7 decade, Southern ratios increase rate +4 decade. This behavior resembles main source COCl2. troposphere positive found both