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Comparison of OSIRIS derived NO concentrations with coincident ACE-FTS NO measurements in the Antarctic Winter upper mesosphere

Edward Llewellyn(1), Richard Gattinger(1), Ian McDade(2), Ana Luisa Alfaro Suzan(2), Patrick Sheese(2), Chris Boone(3), Kaley Walker(3), Peter Bernath(4), Wayne Evans(2) and Doug Degenstein(1)

(1) University of Saskatchewan, 116 Science Place, Saskatoon, SK S7N 5E2, Canada
(2) York University, Petrie Bldg., Toronto, ON M3J 1P3, Canada
(3) University of Waterloo, , Waterloo, ON N2L 3G1, Canada
(4) University of York, , Heslington, York, United Kingdom

Abstract

The visible region continuum spectrum produced by the NO+O(+M)→NO2(+M)+hv chemiluminescent reaction has been detected in the upper mesospheric dark polar Winter regions by OSIRIS on the Odin spacecraft. Limb radiance profiles of continuum spectra are inverted to obtain volume emission rate altitude profiles for comparison with nearly-coincident ACE-FTS NO density observations from solar occultation at approximately 67º South latitude. Atomic oxygen densities required for the comparison are derived from OSIRIS observations of the O2(b1Σg+-X3Σg-) 0-0 band at 762 nm. The OSIRIS NO2 observations are combined with OSIRIS derived atomic oxygen densities to derive NO densities for comparison with ACE NO observations. Examples of the retrieved NO densities are shown and compared solar occultation measurements. The OSIRIS NO2 continuum observations provide estimates of NO densities that are accurate to approximately 15% in the dark polar regions. The noise-limited detection threshold, averaged over the 80 to 100 km altitude range, is approximately 3x107 NO molecules cm-3. A Southern hemisphere map of derived NO densities is included to demonstrate the potential of the OSIRIS NO2 continuum observations. Due to the Odin orbit northern hemisphere measurements are only possible for about one month each year.

 

Workshop presentation