Accuracy assessment of reanalysis datasets for GPS-PWV estimation using Indian IGS stations observations

GPS PWV (Precipitable Water Vapour) is estimated using three years ECMWF, JRA55, MERRA2, and NCEP datasets for two IGS stations HYDE and IISC in India to assess their accuracies over the Indian region. The NWP derived temperature, pressure, zenith hydrostatic delay (ZHD), zenith wet delay (ZWD), and PWV values are validated using AWS observations and derived products. The obtained PWV values are also compared with the total column water product from ECMWF. The results show absolute mean temperature differences of 1-2 degrees K and pressure differences of 1-4 hPa for HYDE and IISC. NWP models' pressure and temperature values strongly correlate with AWS values with R-2 close to 0.9 in most of the cases. The estimated zenith tropospheric delay (ZTD) shows an average difference between 4 mm and 9 mm with respect to IGS ZTD. The mean differences between NWP and reference PWV values are observed from 1 mm to 3 mm. All the derived products obtained using NWP datasets are close to the reference AWS products. However, PWV derived using ECMWF, JRA55 and NCEP is very much close to AWS PWV and can be used for precise PWV computation in this region.