Phosgene in the UTLS: seasonal and latitudinal variations from MIPAS observations

Year: 2016

Authors: Valeri M., Carlotti M., Flaud J.M., Raspollini P., Ridolfi M., Dinelli B.M.

Autors Affiliation: CNR, ISAC, Via Gobetti 101, I-40129 Bologna, Italy
Univ Bologna, Dipartimento Fis & Astron, Viale Berti Pichat 6-2, I-40127 Bologna, Italy
Univ Bologna, Dipartimento Chim Ind Toso Montanari, Viale Risorgimento 4, I-40136 Bologna, Italy
LISA, 61 Ave Gen Gaulle, Creteil, France
CNR, Ist Fis Applicata Nello Carrara, IFAC, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Italy

Abstract: The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a Fourier transform spectrometer that measured mid-infrared atmospheric limb emission spectra from July 2002 to April 2012 on board the polar-orbiting satellite ENVISAT. We have used MIPAS data to study the latitudinal variations of phosgene (COCl2 or carbonyl chloride) and, for the first time, its seasonal variation in the upper troposphere/lower stratosphere region (UTLS). Retrievals of phosgene were made using the 830-860aEuro-cm(-1) region, corresponding to the nu(5) bands of COCl2. Unfortunately, in that region, the nu(4) band of CFC-11, which is much stronger than COCl2 nu(5), hides the phosgene emission. In order to evaluate seasonality and latitudinal distribution of phosgene we have analysed all the measurements made by MIPAS on days 18 and 20 of each month of 2008 with the optimized retrieval model (ORM) recently upgraded with the multi-target retrieval technique and with the optimal estimation functionality to apply external constraints to the state vector. Average seasonal profiles of phosgene show an evident latitudinal variability with the largest values observed in the tropical regions (maximum a parts per thousand aEuro-35 parts per trillion by volume (pptv) at about 300aEuro-hPa). In the midlatitude and polar regions, the volume mixing ratio (VMR) values do not exceed 30aEuro-pptv and the vertical distributions are less peaked. Our analysis highlights that COCl2 seasonal variability is fairly low, apart from the polar regions.

Journal/Review: ATMOSPHERIC MEASUREMENT TECHNIQUES

Volume: 9 (9)      Pages from: 4655  to: 4663

More Information: This study was supported by the ESA project “Support to MIPAS Level 2 processor Verification and Validation – Phase F” (ESRIN/Contract No. 4000112093/14/I-LG). The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, is a Canadian-led mission mainly supported by the Canadian Space Agency and the Natural Sciences and Engineering Research Council of Canada.
KeyWords: MICHELSON INTERFEROMETER; RETRIEVAL; PROFILES; VALIDATION
DOI: 10.5194/amt-9-4655-2016

Citations: 8
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