Long-term variations of the H₂O volume mixing ratio (top, measured at 7.4 μm) and the SO₂ volume mixing ratio (bottom, measured at 7.4 and 19 μm) between January 2012 and January 2016. The January 2012 and March dataset correspond to evening terminator observations; the 4 other datasets correspond to morning terminator observations. All data were obtained using the lines listed in Table 3, with the exception of the first HDO measurement (January 10, 2012) and the two 19-μm SO₂ measurements of October 4, 2012, which were taken using different transitions (E12, E13). For the conversion from HDO to H₂O abundances on Venus, we assume a D/H ratio of 200 times the VSMOW (Fedorova et al. 2008).