Comprehensive analysis of zenith tropospheric dealy and precipitable water vapor retrieved from BDS-3 B1C and B2a signals

This study presents a comprehensive analysis of ZTD and PWV estimated from BDS-3 new B1C/B2a signal combination. ZTD are firstly estimated using B1C and B2a signals and evaluated with the IGS final products. The average convergence time of ZTD was 1980 s, which was 12.0 % shorter than that from the legacy B1I/B3I signals. This indicated their superiority for real-time operational meteorology. The average RMS value of ZTD were 5.9 mm for all stations, corresponding to an ∼ 7.8 % improvement with respect to the legacy B1I/B3I signal combinations. ZTD error characteristics analysis revealed relationships with station latitudes and seasons, mainly due to the more active water vapor variation in equator region and summer. Afterwards, the converted PWV was assessed using multiple inter-technique datasets. For radiosonde-derived PWV, the RMS for GPS L1W/L2W, BDS-3 legacy B1I/B3I, and BDS-3 new B1C/B2a signals were 2.5, 2.4, and 2.5 mm, respectively, whereas those for the remotely-sensed PWV from MODIS were 4.9, 5.0, and 4.9 mm, respectively. Besides, evaluation with ERA5 showed the average RMS were all 1.7 mm for different GNSS signal combinations. These results prove the feasibility of PWV retrieval using BDS-3 new B1C/B2a signals, which are expected to provide scientific references for further applications.