Atmospheric COCl2 measured by solar occultation spectrometry

Vertical profiles of atmospheric COCl2 (phosgene, carbonyl dichloride) have been measured remotely by the JPL MkIV interferometer during recent balloo n flights. The nu (5) band of COCl2 in the 830 to 860 cm(-1) spectral regio n was used for the analyses, despite its overlap with the stronger nu (4) b and of CCl3F. Upper troposphere COCl2 volume mixing ratios of around 20 ppt v were retrieved, increasing to 25 pptv by 15 km altitude, in good agreemen t with previous aircraft measurements made by in situ techniques. At mid-la titudes the COCl2 peaks at around 30 pptv at 22 km altitude, above which it rapidly drops, reaching zero by 28 km altitude.