Analysis of OBrO, IO, and OIO absorption signature in UV‐visible spectra measured at night and at sunrise by stratospheric balloon‐borne instruments

Abstract

[1] Absorption bands of OBrO, IO, and OIO in the visible region have been investigated in the data of the AMON (''Absorption par les Minoritaires Ozone et Nox'') and SALOMON (''Spectroscopie d'Absorption Lunaire pour l'Observation des Minoritaires Ozone et Nox'') balloon-borne spectrometers used to obtain measurements in the nighttime stratosphere, since 1992 and 1998 respectively. The absorption features initially detected in AMON residual spectra and attributed to OBrO are also observable in SALOMON data with better accuracy. New estimates of OBrO cross-section amplitudes taking into account recent laboratory measurements are used for the OBrO retrieval. A consequence is that previously published OBrO concentration and mixing ratio values are revised downwards of around 40%. Further tests are performed to assess the consistency of the OBrO detection. No correlation exists between OBrO and NO 2 vertical profiles which practically rules out the possibility for the structures ascribed to OBrO absorption to be due to remaining NO 2 contributions. It is shown that variability of OBrO quantities at high latitudes obtained from various AMON and SALOMON flights is possibly linked to the chemical processes involving the production of OClO. At midlatitudes, the exceptional and unexpected conditions of the April 28, 1999 SALOMON flight allow us to observe the drop in OBrO concentrations just after sunrise. As expected, if previous studies of stratospheric iodine species are considered, IO and OIO absorption lines are never detected in the residual spectra. The presence of unknown structures in the residual spectra in the IO and OIO absorption regions is obvious and tends to distort the retrievals. The possibility that these remaining features result from a temperature dependence effect or uncertainties of O 3 and/or NO 2 cross-sections is suggested. Thus, more accurate laboratory measurements and sets of cross-sections for low temperature are needed.INDEX TERMS: 0340 Atmospheric Composition and Structure: Middle atmospherecomposition and chemistry; 0343 Atmospheric Composition and Structure: Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707); 0394 Atmospheric Composition and Structure: Instruments and techniques; 0399 Atmospheric Composition and Structure: General or miscellaneous; KEYWORDS: UV-visible spectroscopy, stratosphere, bromine and iodine species Citation: Berthet, G., J.-B. Renard, M. Chartier, M. Pirre, and C. Robert, Analysis of OBrO, IO, and OIO absorption signature in UVvisible spectra measured at night and at sunrise by stratospheric balloon-borne instruments,

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

“…We find upper limits for the concentrations of both gases which put the strongest constraints on their abundance at the region in the Earth's atmosphere where tropospheric air enters the stratosphere to date. Our findings are consistent with previous studies that conclude undetectably low amounts of IO and OIO in the high-and mid-latitude stratosphere (e.g Wennberg et al, 1997;Pundt et al, 1998;Bösch et al, 2003;Berthet et al, 2003). We point out that the inferred upper limits for IO depend on the absorption cross section used for the spectral retrieval.…”

“…Murphy et al (1998), Murphy and Thomson (2000), and Murphy et al (2007) indeed found iodine in upper tropospheric and lower stratospheric particles. Most studies investigating the abundances of inorganic iodine species (IO and/or OIO) in the stratosphere conclude undetectably low amounts (Wennberg et al, 1997;Pundt et al, 1998;Bösch et al, 2003;Berthet et al, 2003). To date, the lowest estimate for the upper limit of the total gaseous inorganic iodine (I y ) burden in the high-and mid-latitude lower stratosphere is ∼0.1 ppt (Bösch et al, 2003).…”

Injection of iodine to the stratosphere

“…Ground-based observations in Arizona (United States) determined an upper limit for total inorganic iodine (I y ) of 0.2 pptv in the stratosphere [Wennberg et al, 1997]. Balloon-borne UV-Visible spectra derived lower stratospheric upper limits of around 0.1 pptv for both IO and OIO in the northern high and middle latitudes [Bösch et al, 2003], as well as over the tropics [Butz et al, 2009], consistent with previous reports. There is, however, one exception of a study reporting stratospheric IO mixing ratios of 0.65 and 0.8 pptv above Spitzbergen [Wittrock et al, 2000].…”

“…There have been several attempts to detect iodine oxides (IO and OIO) in the upper troposphere-lower stratosphere [Berthet et al, 2003;Bösch et al, 2003;Butz et al, 2009;Pundt et al, 1998;Wennberg et al, 1997;Wittrock et al, 2000]. Ground-based observations in Arizona (United States) determined an upper limit for total inorganic iodine (I y ) of 0.2 pptv in the stratosphere [Wennberg et al, 1997].…”

“…Since then, the subsequent World Meteorological Organization (WMO) and United Nations Environment Programme Ozone Assessment Reports [WMO, 2014], based on available remotesensing measurements at twilight [Berthet et al, 2003;Bösch et al, 2003;Butz et al, 2009;Pundt et al, 1998;Wennberg et al, 1997], suggested upper limits of 0.1 pptv of IO and a total I y of <0.15 pptv, leading to an estimated negligible role of iodinated gases on stratospheric ozone photochemistry [WMO, 2014]. Consequently, global assessments on climate change have thus far only considered the stratospheric ozone depletion potential of long-and short-lived bromocarbons and chlorocarbons [WMO, 2014].…”