Augmentation Method for Weighted Mean Temperature and Precipitable Water Vapor Based on the Refined Air Temperature at 2 m above the Surface of Land from ERA5

Due to the difference in the quality of the global assimilation data and the ability to reproduce the real conditions of the atmosphere, the hourly atmospheric temperature at 2 m above the land surface from ERA5 cannot be used with complete confidence for the atmospheric weighted mean temperature (Tm) calculations and global navigation satellite system (GNSS) precipitable water vapor (PWV) inversion. A systematic and complete refinement method is proposed, including the compensation of elevation matching bias of gridded temperature, correction of fixed-time cusp data fitting and refinement based on the remove-and-restore model. The usability and accuracy improvement of the refined ERA5 2 m atmospheric temperature in the Tm and PWV calculation were validated based on three GNSS stations. The result shows that the average accuracy of the Tm and PWV for the entire region could be increased by 74.4% and 75.1%, respectively. The RMS of the highest station was reduced from 4.28 K to 0.62 K for the Tm and 0.662 mm to 0.203 mm for the PWV, and the RMS of other stations was reduced from 1.25 to 0.44 K for the Tm and 0.211 mm to 0.101 mm for the PWV. This overall refinement method has important implications for atmospheric remote sensing.