Observations of lower-stratospheric ClONO{sub 2}, HNO{sub 3}, and aerosol by the UARS CLAES experiment between January 1992 and April 1993
- Lockheed Palo Alto Research Lab., CA (United States)
- Lawrence Livermore National Lab., CA (United States)
This paper discusses simultaneous measurements of stratospheric ClONO{sub 2}, HNO{sub 3}, temperature, and aerosol extinction coefficient by the Cryogenic Limb Array Etalon Spectrometer (CLAES) on the NASA Upper Atmosphere Research Satellite (UARS), obtained over the period 9 January 1992 through 23 April 1993. The discussion concentrates on the stratosphere region near 21 km of particular interest to heterogeneously driven ozone depletion. For periods between 12 June and 1 September 1992 at latitudes poleward of about 60{degrees}S, when temperatures were below type I polar stratospheric cloud (PSC) formation thresholds throughout the lower stratosphere, CLAES observed high levels of PSCs coincident with highly depleted fields of both HNO{sub 3} and ClONO{sub 2}. By 17 September, the incidence of PSCs had greatly diminished in the lower stratosphere, but both ClONO{sub 2} and HNO{sub 3} remained highly depleted. These observations are consistent with the removal of gaseous HNO{sub 3} through the formation of nitric acid trihydrate (NAT) particles and the removal of ClONO{sub 2} through heterogeneous reactions on the particle surfaces. They also suggest substantial denitrification of the lower Antarctic vortex through sedimentation of PSC particles. In the Northern Hemisphere winter of 1992/93 far fewer PSCs were observed in the Arctic lower-stratosphere vortex, which had shorter periods and more localized regions of cold temperatures. Both HNO{sub 3} and ClONO{sub 2} maintained much higher levels inside the Arctic vortex than those seen in the Antarctic throughout the winter/spring period. Following 28 February 1993 when Arctic vortex temperatures rose above 195 K, ClONO{sub 2} was observed in large quantities inside the vortex. The persistence of relatively high levels of HNO{sub 3} inside the Arctic spring vortex compared with the low levels seen in the Antarctic spring vortex suggest a much lower level of denitrification in the Arctic. 33 refs., 19 figs.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 41694
- Journal Information:
- Journal of the Atmospheric Sciences, Journal Name: Journal of the Atmospheric Sciences Journal Issue: 20 Vol. 51; ISSN 0022-4928; ISSN JAHSAK
- Country of Publication:
- United States
- Language:
- English
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