Monthly Climatologies of Water Vapor in the Extratropical Lowermost Stratosphere

This dataset contains 16 NetCDF climatology files assembled for the study *Seasonality of Water Vapor in the Lowermost Stratosphere* (manuscript submitted to *Geophysical Research Letters*). The collection supports analyses of the seasonal cycle of water vapor in the extratropical lowermost stratosphere using CLaMS-3.0 simulations, ERA5 meteorological fields, satellite observations, and in-situ measurements. The archive includes CLaMS and ERA5-based climatologies; processed climatologies from SWOOSH v2.74, Aura Microwave Limb Sounder (MLS) v6.0, ESA Climate Change Initiative (CCI) water vapor, and ACE-FTS v5.2; and stratospheric-subset climatologies from NDACC frost-point hygrometer observations and JULIA/TPChange in-situ measurements. The NDACC and JULIA/TPChange files also provide CLaMS and ERA5 values sampled at the observational locations. The MLS-related files include an MLS climatology, a corresponding CLaMS climatology, and a CLaMS climatology processed with MLS averaging-kernel smoothing. Monthly climatologies are organized by geographical latitude or equivalent latitude and pressure, depending on the product. Two additional tropopause climatologies support tropopause-relative analyses. Coverage varies by product and is indicated in the filenames (2002–2025 across the collection). The files retain source-specific units and metadata conventions; consult `README.md` for the complete inventory, water-vapor unit conversions, provenance notes, and cautions concerning inherited NetCDF attributes.