Upper Limits of Stratospheric IO And OIO Inferred From Center to Limb Darkening Corrected Balloon-Borne Solar Occultation Visible Spectra; Implications For Total Gaseous Iodine And Stratospheric Ozone
Abstract
We report on upper limits of lower stratospheric IO (mean 0.151~ppt; 0.087~ppt; 0.072~ppt and lowest value 0.1~ppt; 0.069~ppt; 0.06~ppt at 20, 15, 12.5~km, respectively) and OIO (mean 0.157~ppt; 0.075~ppt; 0.057~ppt and lowest value 0.1~ppt; 0.059~ppt; 0.043~ppt at 20, 15, 12.5~km, respectively) inferred from balloon-borne solar occultation UV/visible spectroscopy (<20~km). The spectra were recorded during a series of LPMA/DOAS (Laboratoire de Physique Moléculaire et Applications/Differential Optical Absorption Spectroscopy) balloon flights that were conducted at different geophysical conditions i.e., inside the arctic winter vortex, at mid-, and high latitudes in spring, summer, and fall. Photochemical modeling that accounts for the iodine partitioning during the observations allows us to infer upper limits of total inorganic gas-phase iodine (Iy). Combining our measurements with photochemical modeling reveals a lower stratospheric Iy (< 20 km) of <=0.1+/-0.02~ppt and <=0.065+/-0.01~ppt taking into account, and neglecting OIO photolysis, respectively. For the middle stratosphere, the inferred total Iy is larger due to the smaller detection sensitivity there. The inferred small upper limit for stratospheric Iy provokes the following questions; does much less iodine enter the stratosphere than the amount expected from the tropopause entry level (primarily the tropical upper troposphere), or does it reside in other minor gaseous species, or eventually in a non-gaseous, i.e., particulate form, in the stratosphere ? The implication of our iodine measurement on stratospheric ozone is also briefly discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.A52A0096B
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE