Two-Step Precipitable Water Vapor Fusion Method

Precipitable water vapor (PWV) is one of the key parameters in the evolution of extreme weather and climate change. However, current data fusion methods (such as Gaussian processes, spherical cap harmonics, and polynomial fitting) can hardly obtain simultaneously the PWV map with high precision and high spatiotemporal resolution. To solve this problem, a two-step-based PWV fusion (TPF) method is proposed, in which a hybrid PWV fusion model (HPFM) and a spatial and temporal fusion model (STFM) are introduced separately. In the first step, HPFM is established by combining the global pressure and temperature 2 wet (GPT2w) model, spherical harmonic functions, and polynomial fitting to obtain the PWV value with high precision at an arbitrary location in the study area. In the second step, STFM is proposed to generate the PWV map with high temporal resolution taking advantage of site-based global navigation satellite system (GNSS)-derived PWV. To validate the performance of the proposed method, GNSS observations, ERA-Interim, and ERA5 reanalysis products are selected in Yunnan Province, China, to carry out the experiment. Statistical results show that: 1) HPFM has the ability to obtain atmospheric water vapor with a root mean square (rms) of less than 3 mm in an arbitrary location of the PWV map and 2) STFM can generate PWV maps with the same temporal resolution as GNSS observations, and the accuracy of the obtained PWV values can be guaranteed. Therefore, the proposed TPF method is proven to have the ability to simultaneously retrieve PWV maps with high accuracy and spatiotemporal resolution.