Red curve: summation of all longitudes observed by TEXES over the 2012–2019 period. This curve is the same as the red curve in Fig. 18. Blue curve: summation of all SO₂ vmr distributions vs longitude, using the same dataset. For each observation, the normalized distribution of the SO₂ vmr as a function of longitude is calculated as described in the text. The sum of all SO₂ vmrs has been divided by 400.0 ppbv. Thick points: results with the whole dataset (2012–2019); thin points: dataset without the 2019 data.