8.2.3 Ozone

As noted above, ozone is mostly concentrated between 11 and 40 km altitude; it shows large seasonal and, mostly, latitude variation. Because of its high altitude location, its lines are narrow: at 25 km, $\rho_a$, hence $\Delta\nu$, is reduced by a factor of 20 with respect to see level; moreover, the dipole moment of ozone ($\mu$= 0.53 D), 3.5 times smaller than that of H₂O, further reduces the ozone line widths.

Because of their small widths and despite the small ozone abundance, ozone lines have significant peak opacities, especially above 230 GHz ( $\tau_o= 0.2-0.3$).