HR: 14:20h
AN: A43D-03    [Abstracts]
TI: Chlorine Reservoir Partitioning in the Polar Stratosphere Revealed by ILAS and HALOE data
AU: * Hayashida, S
EM: sachiko@ics.nara-wu.ac.jp
AF: Nara Women's University, Kita-uoya Nishi-machi, Nara, 630-8506 Japan
AU: Ikeda, N
EM: ikeda@ics.nara-wu.ac.jp
AF: Nara Women's University, Kita-uoya Nishi-machi, Nara, 630-8506 Japan
AU: Toda, Y
EM: yoko@ics.nara-wu.ac.jp
AF: Nara Women's University, Kita-uoya Nishi-machi, Nara, 630-8506 Japan
AU: Nakajima, H
EM: hide@nies.go.jp
AF: National Institute for Environmental Studies, Onogawa16-2, Tsukuba, 305-8506 Japan
AB: Partitioning of chlorine reservoirs in the polar stratosphere was analyzed by utilizing two occultation sensors, the Improved Limb Atmospheric Spectrometer (ILAS) and the HALogen Occultation Experiment (HALOE). The ILAS was on board the Advanced Earth Observing Satellite (ADEOS), and continued regular operation from November 1996 through June 1997. ILAS monitored profiles of O$_{3}$ and ozone-related species, such as aerosols (or PSCs), HNO$_{3}$, NO$_{2}$, N$_{2}$O, CH$_{4}$, and water vapor on a regular basis, 14 times daily at high latitudes in the both hemispheres. The newest retrieval algorithm (Version 6.0) of the ILAS successfully derives chlorine nitrate (ClONO$_{2}$) profiles in both hemispheres. The HALOE was launched on the Upper Atmosphere Research Satellite (UARS) spacecraft in September 1991, which measured vertical profiles of O$_{3}$, HCl, HF, CH$_{4}$, H$_{2}$O, NO, NO$_{2}$, aerosol extinction, and temperature. Combined analysis of HCl/HALOE and ClONO$_{2}$/ILAS helps to elucidate chlorine reservoir partitioning, ClONO$_{2}$/HCl over polar regions and inform estimates of ozone loss by chemical processes. Difference in the latitudinal coverage of the two sensors limits the period of simultaneous analysis to several months for both hemispheres. However, these months include recovery periods after ozone depletion in both hemispheres and an inter-hemispheric comparison is therefore possible. In February and March 1997, some of the ClONO$_{2}$ data showed significant enhancement of ClONO$_{2}$ that peaked at ~2 ppbv in the vortex on the 475-K isentropic surface, which indicates deactivation of active chlorines into ClONO$_{2}$. Low HCl values observed with HALOE during corresponding period in the vortex confirm deactivation of active chlorine to ClONO$_{2}$ rather than HCl. For the Southern Hemisphere, the mixing ratios of ClONO$_{2}$ on the 475-K surface were extremely low, while HCl is relatively high in the vortex. In the Arctic summer, after a temporary enhancement of ClONO$_{2}$ in late spring, the chlorine partitioning should gradually shift toward HCl from ClONO$_{2}$. When photochemical balance between ClO-ClONO$_{2}$ and HCl-Cl reactions is assumed, the [ClONO$_{2}$]/[HCl] ratio has a linear correlation to [O$_{3}$]$^{2}$/[CH$_{4}$] [Dessler et al., 1995]. In boreal summer (May and June), [ClONO$_{2}$]/[HCl] ratios derived by ILAS and HALOE show a good linearity to [O$_{3}$]$^{2}$/[CH$_{4}$] derived by ILAS measurements at altitudes from 14 to 24 km. The two major species of inactive chlorines are HCl and ClONO$_{2}$: the sum of the two species indicates total Cly approximately except for activated chlorines. The correlation of Cly ($\sim$ ClONO$_{2}$ + HCl) versus N$_{2}$O/ILAS is almost consistent with the correlation estimated by Woodbridge et al. [1995], though the derived Cly is slightly larger than the estimate of Woodbridge et al at higher altitudes. References Dessler et al., GRL, 22, 1721-1724, 1995. Woodbridge et al., GRL, 100, 3057-3064, 1995.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting