Stratospheric water vapor (SWV) is well known to be a greenhouse gas. Because of its importance to the climate, the long-term trend of SWV has long been studied. In this study, we use a new method-dynamical linear model-to reassess long-term variations and trends of the tropical SWV over the past three decades (1991 to 2024). We add more comprehensive regressors, including ENSO, QBO, Brewer-Dobson circulation, solar cycle and stratospheric aerosols, that have an effect on SWV, and quantify the contribution of these regressors. In addition, we discuss the effects of two volcano events on long-term trends of SWV, namely the 1991 Mount Pinatubo eruption and 2022 Hunga Tonga-Hunga Ha’apai eruption.

volcanic eruption,dynamical linear model,long-term trend,stratospheric water vapor,stratospheric aerosols