The seasonal trends in the anti-Jovian and sub-Jovian equatorial SO₂ column abundances. The anti-Jovian data cover longitudes of 120^∘W–240^∘W and are normalized to 180^∘W. The sub-Jovian data cover longitudes of 300^∘W–60^∘W and are normalized to 360^∘W. For each hemisphere, the dashed–dotted curve shows the best-fit seasonal model, combining the SO₂ frost vapor-pressure equilibrium curve (dotted curve) and the constant, presumed volcanic, component (solid horizontal line).