An improved global pressure and zenith wet delay model with optimized vertical correction considering the spatiotemporal variability in multiple height-scale factors

Abstract. Atmospheric pressure and zenith wet delay (ZWD) are essential for global navigation satellite system (GNSS) tropospheric correction and precipitable water vapor (PWV) retrieval. As the development progresses of real-time GNSS kinematic technology, moving platforms, such as airborne and shipborne, require high-quality tropospheric delay information to pre-correct errors. Most existing tropospheric models are only applicable to the Earth's surface and exhibit poor accuracies in high-altitude areas due to simple vertical fitting functions and limited temporal resolution of the underlying parameters. Hence, an improved global empirical pressure and ZWD model is developed using 5-year ERA5 hourly reanalysis data, called IGPZWD, which takes seasonal and intraday variations into consideration. The vertical accuracy and applicability of IGPZWD model are further optimized by introducing the annual and semi-annual harmonics for pressure and ZWD height-scale factors of exponential function with three orders. Taking the ERA5 and radiosonde profile data in 2020 as reference, the pressure and ZWD of IGPZWD model show superior performance compared to those of three state-of-the-art models, i.e., GPT3, IGPT, and GTrop. Furthermore, IGPZWD-predicted zenith tropospheric delay (ZTD) yields improvements of up to 65.7 %, 2.4 %, and 7.8 % over that of GPT3, RGPT3, and GTrop models on a global scale, respectively. The proposed vertical correction algorithm effectively weakens the impact of accumulation error caused by excessive height difference, achieving optimal accuracy and feasibility in the high-altitude area. The IGPZWD model can be extensively applied in GNSS kinematic precision positioning, as well as atmospheric water vapor sounding.