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Sökning: WFRF:(Plane J. M.C.) > (2005-2009)

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  • Gumbel, Jörg, et al. (författare)
  • Retrieval of global mesospheric sodium densities from the Odin satellite
  • 2007
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:L04813
  • Tidskriftsartikel (refereegranskat)abstract
    • Satellite observations of the Na D dayglow at 589 nm provide a global database for the climatology of the mesospheric sodium layer. More than five years of Na D limb observations are available from the Optical Spectrograph and InfraRed Imager System onboard the Odin satellite. We describe a robust retrieval method that provides individual sodium density profiles with a typical accuracy of 20% and altitude resolution of 2 km. Retrieved column abundances and density profiles are validated against sodium resonance lidar measurements at mid- latitudes. Examples of the seasonal and latitudinal variation of the sodium layer illustrate Odin's potential for climatological studies of mesospheric metals.
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3.
  • Slanger, Tom G., et al. (författare)
  • Variability of the mesospheric nightglow sodium D2/D1 ratio
  • 2005
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 110:23, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements of the intensity ratio of the 589.0/589.6 nm sodium doublet in the terrestrial nightglow over an 8-year period, involving >300 separate determinations, have established that it is variable, the value RD = I(D2)/I(D1) lying between 1.2 and 1.8. Sky spectra from the Keck I telescope with the High-Resolution Echelle Spectrometer (HIRES) échelle spectrograph and the Keck II telescope with the Échellette Spectrograph and Imager (ESI) échelle spectrograph were used in this analysis. The result contrasts with the accepted view, from earlier measurements at midlatitude, that the ratio is 2.0, as expected on statistical grounds. The lack of dependence of the ratio on viewing elevation angle, and hence Na slant column, allows self-absorption to be ruled out as a cause of the variability. The data suggest a semiannual oscillation in the ratio, maximum at the equinoxes and minimum at the solstices. Airborne measurements over the North Atlantic (40°-50°N) in 2002 show an even larger range in the nightglow ratio and no correlation with the upper mesospheric temperature determined from the OH 6-2 bands. A laboratory study confirms that the ratio does not depend on temperature; however, it is shown to be sensitive to the [O]/[O2] ratio. It is therefore postulated that the variable ratio arises from a competition between O reacting with NaO(A3∑+), produced from the reaction of Na with O3, to yield D-line emission with a D2/D1 ratio greater than about 2.0, and quenching by O2 to produce NaO(X2II), possibly with vibrational excitation, which then reacts with O to produce emission with a ratio of less than 1.3. Copyright 2005 by the American Geophysical Union.
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