Typical Jacobian kernels. Top: Sensitivity of the forward model in the vertical distribution of CO₂ number density. The different colours correspond to each altitude bin that is defined by the observational measurements. Bottom: Sensitivity of the quantum yield to the corresponding altitude grid. Different colours correspond to different wavelengths with lnm resolution from 80 to 128nm. With dashed black line we show the Ly – α line divided by a factor of 10. It is not surprising that Ly – α shows this sensitivity, since the production of the lower peak is almost solely produced by it.