Long‐Term Variability of Homogenized GPS‐Derived Precipitable Water Vapor Over Chinese Stations (2000–2020)

As a vital atmospheric component, water vapor influences climate change and drives numerous weather‐related processes. The Global Positioning System (GPS) provides a valuable tool for investigating Precipitable Water Vapor (PWV). This study reanalyzed the raw GPS data from 2000 to 2020 at 25 stations over China to generate a consistent and reliable GPS PWV data set. To obtain homogenized GPS PWV time series, potential artificial shifts in the mean caused by changes in instruments and environmental conditions were identified and corrected based on GPS station log files and comparisons with numerical weather prediction reanalysis PWV from the ECMWF Reanalysis v5 (ERA5) and satellite PWV observations from the Moderate Resolution Imaging Spectrometer (MODIS). A comprehensive assessment of the spatiotemporal variability of PWV is performed using this homogenized GPS data set, while using the ERA5 and the MODIS PWV products for comparison. We first found that both ERA5 and MODIS are slightly wetter than GPS PWV, and ERA5 agrees better with GPS PWV than MODIS does. The annual PWV trends are generally significantly positive across China, and exhibit a west‐to‐east gradient in increasing PWV. The homogenized GPS PWV shows a wetting in eastern and central China during summer and a drying or no trend in winter over central and northern China. The relationships among PWV, specific humidity, and precipitation with temperature more closely follow the scale of the Clausius‐Clapeyron expectation in monsoon‐dominated regions than in the plateau region. This study provides new insights into China's atmospheric moisture dynamics in a changing climate.