The budget and partitioning of stratospheric chlorine during the 1997 Arctic summer (original) (raw)

1999, Journal of Geophysical Research

Volume mixing ratio profiles of HCl, HOC1, ClN03, CH3C1, CFC-12, CFC-11, CC14, HCFC-22, and CFC-113 were measured simultaneously from 9 to 38 km by the Jet Propulsion Laboratory MkIV Fourier Transform Infrared solar absorption spectrometer during two balloon flights from Fairbanks, Alaska (64.8"N) on 8 May and 8 July 1997, The altitude variation of total organic chlorine (CCl,), total inorganic chlorine (Cl,), and the nearly constant value (3.7h0.2 ppbv) of their sum (ClTOT) demonstrates that the stratospheric chlorine species available to react with O3 are supplied by the decomposition of organic chlorinated compounds whose abundances are well quantified. Measured profiles of HC1 and ClN03 agree well with photochemical model values (differences < 10% for altitudes below 34 km), particularly when production of HC1 by ClO+OH is included in the model. Our results demonstrate that the production of HC1 by C10 + OH plays a small role (< 5%) in the partitioning of HC1 and ClN03 for the sampled air masses for altitudes below-28 km because the concentration of C10 is suppressed during summer at high latitudes. Both the measured and calculated [ClN03]/[HCl] ratios exhibit the expected near linear variation with [03I2/[CH4] over a broad range of altitudes. MkIV measurements of HC1, ClN03, and CC1, agree well with ER-2 in situ observations of these quantities for directly comparable air masses. These results demonstrate good understanding of the budget of stratospheric chlorine and that the partitioning of inorganic chlorine is accurately described (differences < 10%) by photochemical models that employ JPL97 reaction rates for the environmental conditions encountered: relatively warm temperatures, long periods of solar illumination, and relatively low aerosol surface areas.