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. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) measuredthe middle-infrared limb emission spectrum of the atmosphere from 2002 to 2012on board ENVISAT, a polar-orbiting satellite. Recently, the European SpaceAgency (ESA) completed the final reprocessing of MIPAS measurements, usingversion 8 of the level 1 and level 2 processors, which include more accuratemodels, processing strategies, and auxiliary data. The list of retrieved gaseshas been extended, and it now includes a number of new species with weak emissionfeatures in the MIPAS spectral range. The new retrieved trace species includecarbonyl chloride (COCl2), also called phosgene. Due to itstoxicity, its use has been reduced over the years; however, it is still used bychemical industries for several applications. Besides its direct injection inthe troposphere, stratospheric phosgene is mainly produced from the photolysisof CCl4, a molecule present in the atmosphere because of humanactivity. Since phosgene has a long stratospheric lifetime, it must becarefully monitored as it is involved in the ozone destruction cycles,especially over the winter polar regions. In this paper we exploit the ESA MIPAS version 8 data in order to discuss thephosgene distribution, variability, and trends in the middle and lowerstratosphere and in the upper troposphere. The zonal averages show thatphosgene volume mixing ratio is larger in the stratosphere, with a peak of40 pptv (parts per trillion by volume) between 50 and 30 hPa at equatorial latitudes,while at middle and polar latitudes it varies from 10 to25 pptv. A moderate seasonal variability is observed in polarregions, mostly between 80 and 50 hPa. The comparison ofMIPAS–ENVISAT COCl2 v8 profiles with the ones retrieved fromMIPAS balloon and ACE-FTS (Atmospheric ChemistryExperiment – Fourier Transform Spectrometer) measurements highlights a negative bias of about2 pptv, mainly in polar and mid-latitude regions. Part of this biasis attributed to the fact that the ESA level 2 v8 processor uses an updatedspectroscopic database. For the trend computation, a fixed pressure grid isused to interpolate the phosgene profiles, and, for each pressure level, VMR (volume mixing ratio)monthly averages are computed in pre-defined 10∘ wide latitudebins. Then, for each latitudinal bin and pressure level, a regression modelhas been fitted to the resulting time series in order to derive theatmospheric trends. We find that the phosgene trends are different in the twohemispheres. The analysis shows that the stratosphere of the NorthernHemisphere is characterized by a negative trend of about−7 pptv per decade, while in the Southern Hemisphere phosgenemixing ratios increase with a rate of the order of +4 pptv per decade. This behavior resembles the stratospheric trendof CCl4, which is the main stratospheric source of COCl2. Inthe upper troposphere a positive trend is found in both hemispheres.

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