Responsible: Jörg Gumbel, Tomas Waldemarsson, in collaboration with Zeyu Fan, John Plane (University of East Anglia, U.K.)
In close collaboration with John Plane at the University of East Anglia, U.K., a specific OSIRIS project is devoted to the climatology of mesospheric sodium. The sodium atom belongs to the family of metal atoms of meteoric origin (Na, K, Fe, Mg and Ca) found between 80 and 120 km. These atoms are part of a number of chemical cycles involving both ions and neutral species. Specifically, the sodium bicarbonate molecule, postulated as an end product of these reactions, has been proposed as a potential condensation nucleus for NLC particles. Lidar experiments and our own earlier rocket experiments show that during the summer the sodium concentration is strongly reduced, and below 85 km the atom is completely depleted.
Our study addresses the relation between the free sodium density on one hand and the dynamic and chemical evolution of the mesopause region during the summer season on the other. Obviously, sodium and related compounds are also closely connected to the objectives of the MAGIC project with its focus on metallic condensates in the mesosphere. The following scientific topics are addressed in this study:
The Odin remote sensing of the sodium abundance is based on the resonant scattering of sunlight at 589 nm. The dayglow intensity of the sodium D-lines is about 2 kR which is seen as a distinct feature in the OSIRIS spectra. Resonance radiative transfor code, a forward model for the sodium dayglow, and optimal estimation retrieval techniques have been developed at MISU. Retrieved vertical profiles of sodium concentrations have been validated against ground-based lidar measurements. An assessment of the global climatology of the sodium layer is now under way. Future plans comprise similar studies for iron and potassium atoms.
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Last updated: January 11, 2006
Jörg Gumbel (gumbel@misu.su.se)