Minimize SCIAMACHY Product Handbook

Derivation of Tropospheric Information

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The retrieval range is limited at lower altitudes because the atmosphere becomes optically thick with respect to Rayleigh scattering and/or O3 absorption. Above about 40 km the O3 absorption signatures become too weak to be observed. However, normalised limb radiance profiles in the O3 Hartley and Huggins bands can also be used without further wavelength pairing for the derivation of ozone profiles in the upper stratosphere and lower mesosphere (Rohen et al. 2006). The O3 retrievals may be extended up to at least 65 km since the absorption cross sections in the Hartley and Huggins bands are significantly larger than in the Chappuis band.
The wide variety of retrieval algorithms currently applied to SCIAMACHY limb and occultation data are summarised in table 5-3, together with their corresponding references.

 

Parameter  Spectral Window (nm)  Layer  Quantity  Retrieval Algorithm Reference  
O3  525, 600, 675525-590   stratosphere  profile  von Savigny et al. 2005 a Doicu et al. 2002, Doicu 2005  
  240-310 (selected wavelengths)  mesosphere  profile  Rohen et al. 2006 
  520-595  stratosphere  profile sun occultation  Meyer et al. 2005 
  510-560  stratosphere  profile moon occultation  Amekudzi et al. 2005a 
NO2  425-450(70)   stratosphere  profile limb  Rozanov et al. 2005 b Sioris et al. 2004 Doicu et al. 2002, Doicu 2005  
  420-460  stratosphere  profile sun occultation  Meyer et al. 2005 
  430-460  stratosphere  profile moon occultation  Amekudzi et al. 2005a 
NO3  610-680  stratosphere  profile moon occultation  Amekudzi et al. 2005b 
BrO  335-360   stratosphere  profile  Rozanov et al. 2005 b Dorf et al. 2005  
OClO  365-389   stratosphere  profile   
NLC  265-300  mesosphere  indicator, particle radius  von Savigny et al. 2004a 
PSC  750, 1090  stratosphere  indicator  von Savigny et al. 2005b 
Tmesopause  1515-1550  mesosphere  nighttime temperature at mesopause  von Savigny et al. 2004b 

Table 5-3: Atmospheric geophysical parameters and retrieval algorithms – limb and occultation.


5.5 Derivation of Tropospheric Information

Of major scientific – and public – interest are distributions of trace gases in the troposphere. Two cases need to be distinguished:


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Constituents with the majority of the atmospheric amount residing in the lower troposphere (e.g. CO, CH4, CO2, HCHO, SO2, H2O): The total column derived from UV-VIS and SWIR solar backscatter measurements with the techniques derived in chapter 5.2 directly represents the tropospheric column amount including the boundary layer under cloud free conditions.

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Trace gases with comparable column amounts in the troposphere and stratosphere (e.g. BrO, NO2) or with the stratospheric amount dominating the total column (e.g. O3): Additional techniques have to be applied to separate tropospheric and stratospheric concentrations.

 

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