Long-term variations of the H₂O volume mixing ratio (top, blue points), inferred from the HDO measurements, and the SO₂ volume mixing ratio (bottom, red points), measured at the cloud top from the TEXES data at 7.4 μm. A daily mean is shown in this figure. The black squares are the mean values of the H₂O and SO₂ mixing ratios averaged over each run. In 3 cases (Dec. 2017–Jan. 2018, July-Sept. 2018, Feb.–Apr. 2019), we have co-added alldata (separated by less than 3 months), in order to have a more homogeneous time sampling over the long term.