Vertical profiles (solid lines) used as inputsto the ATM model for the model spectra shown in this work. The dots indicate the average values for the different layers (of increasing thickness) in which the atmosphere has been divided for the calculations. Dashed lines and open circles indicate profiles from U.S. Standard Atmosphere (COESA 1976) before being modified for a better fit to the observed lines of O₃, N₂O, HCl, and CO.