Institut für Umweltphysik/Fernerkundung Physik/Elektrotechnik Fachbereich 1 [email protected]SADDU June 2008 S. Noël, K.Bramstedt, A. Rozanov IFE/IUP, University of Bremen, Germany Water Vapour Profiles from SCIAMACHY Solar Occultation Measurements - Preliminary Results -
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Institut für Umweltphysik/Fernerkundung Physik/Elektrotechnik Fachbereich 1 [email protected] SADDU June 2008 S. Noël, K.Bramstedt,
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Institut für Umweltphysik/Fernerkundung Physik/ElektrotechnikFachbereich 1
• Advantages:– Simple DOAS-like approach– Uses pre-calculated data base; no individual radiative transfer model
calculations required– Numerically very fast
• Limitations:– Dependence of optical depths and saturation correction on model
atmosphere– Saturation correction not only function of density but also light path
(but: no significant changes in results when using n(z))– Multiplicative saturation correction factor may not be sufficient– Downward propagation of errors
Institut für Umweltphysik/Fernerkundung Physik/ElektrotechnikFachbereich 1
– 0 – 50 km– 1 km steps until 25 km; 2.5 km steps above
(matching RTM altitude grid)
• Use subset of SCIAMACHY measurements: – Currently only state 49 used (nominal scan)– Only upward scans & 4 readouts close to solar centre– Only tangent altitudes below 60 km– Ratio to spectra above atmosphere for matching
readouts / position on sun
• SCIAMACHY spectra are interpolated to retrieval grid
• Retrieved profiles are interpolated back to SCIAMACHY altitude grid
• Only useful results above ~ 15 km
Reference
Institut für Umweltphysik/Fernerkundung Physik/ElektrotechnikFachbereich 1
• Improvement of saturation correction:– Parameterisation of saturation?– Non-linear correction?
• Field-of-View integration / altitude shift?• Optimisation of altitude grid• Optimisation of fitting window• Different reference atmosphere?• Comparison with optimal estimation method (K.