High-precision GNSS PWV retrieval using dense GNSS sites and in-situ meteorological observations for the evaluation of MERRA-2 and ERA5 reanalysis products over China

Precipitable water vapor (PWV) product with high accuracy and spatiotemporal resolution is important for climate change research. Hourly PWV products a can be provided by global navigation satellite system (GNSS) reanalysis data. The National Aeronautics Space Administration (NASA) the European Center Medium-Range Weather Forecasts (ECMWF) have recently released their of Modern-Era Retrospective Analysis Research Applications, Version 2 (MERRA-2) fifth-generation ECMWF Reanalysis (ERA5), respectively. A comprehensive evaluation these two over China has yet to fully investigated. In this study, MERRA-2 ERA5 been systematically evaluated based on 339 GNSS sites in-situ ground meteorological observations from year 2016 2018. To mitigate uncertainties evaluation, three enhanced vertical correction models temperature, pressure that we developed previously are adopted. Four weighted mean temperature ( T m ) established four regions (North China, South Tibet Plateau, Northwest China), they exhibit better than other classical in China. results MERRA-2- ERA5-derived show correlation coefficient, biases, root square error (RMSE) 0.98/0.99, −0.51/0.38 mm, 2.50/1.99 They both relatively large difference when applied For same grid spatial resolution, exhibits similar performance MERRA-2. monthly-mean-reanalysis-derived obvious seasonality largest summer. provide more details pattern compared PWV. diurnal anomaly variation consistent data, some differences at certain moments during autumn winter observed. These excellent applicability help us efficiently use research • High derived dense stations reliable evaluation. Enhanced T, P PWV, used. Comprehensive in-depth consistency analysis GNSS, MERRA-2, products.