The stratospheric slant column density, SCD_strat, that is the concentration of NO₂ in the stratospheric slant is determined.

Fig 3.4.1.6.1: The stratospheric slant column density, SCD_strat.

Image: AT2-ELS

Depending on the instrument being used, this can be done in two different ways:

• In the case of data from GOME, calculating the SCD_strat from a stratospheric 'reference sector'.
• In the case of data from SCIAMACHY, calculating the SCD_strat from direct limb mode measurements of the stratosphere above the ground pixel.