Validation of SAGE III/ISS stratospheric water vapor

The Stratospheric Aerosol and Gas Experiment instrument on the International Space Station (SAGE III/ISS) has been retrieving vertical profiles of water vapor and other trace gas concentrations since mid-2017. We present intercomparisons of coincident water vapor profile measurements made by SAGE III/ISS and both the Aura Microwave Limb Sounder (MLS) and balloon-borne frost point hygrometers (FP). We also present seasonal and year-to-year variability in stratospheric water vapor measured by the SAGE III-ISS instrument, and compare this variability to that observed by MLS. The early results demonstrate reasonable agreement between SAGE III/ISS and MLS variability, and that SAGE III/ISS has a relative dry bias of ~ 10 % compared to MLS and FP measurements.