Stratospheric water vapor (SWV) is an important greenhouse gas for the radiative budget and for understanding of stratospheric transport. Merged water vapor measurements and long-term simulations with chemical transport models (CTMs) driven by reanalyses are two widely-used means of reconstructing the long-term record of SWV over the past 3-4 decades. The natural variability of SWV entering the stratosphere spans a large range of time scales. We show preliminary results of SWV simulations for the period of 1980–2013 using the Chemical Lagrangian Model of Stratosphere (CLaMS) driven by three modern reanalysis products, which allow us to quantitively estimate uncertainties in modelled SWV related to the input reanalysis fields.