Implementation of Ready-Made Hydrostatic Delay Products for Timely GPS Precipitable Water Vapor Retrieval Over Complex Topography: A Case Study in the Tibetan Plateau
IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING(2021)
摘要
For the timely retrieval of global positioning system based precipitable water vapor (GPS-PWV) over complex topography when there is no in situ pressure-derived zenith hydrostatic delays (ZHDs), this article evaluates three types of ready-made ZHD products, including two newly released products from the Vienna University of Technology (TU Wien, TUW-VMF3) and GeoForschungsZentrum Potsdam (GFZ-VMF1) and a legacy product TUW-VMF1. We implement them for the first time for GPS-PWV retrieval in regions with highly variable topography, such as the Tibetan plateau (TP). First, we present a refined method [model-assisted ZHD height adjustment, model-assisted ZHD height adjustment (MAZHA)] for implementing the above VMF1/VMF3-like ZHD products. The results reveal that the MAZHA method improves the implementation accuracy over the TP by 70% compared to the conventional method. Then, the above multisource VMF1/VMF3-like ZHD products are evaluated using the in situ pressure-derived ZHDs across the TP. The results show that the GFZ-VMF1 outperforms the TUW-VMF1 mainly because a more advanced underlying numerical weather model (ERA5) are adopted. TUW-VMF3 achieves the best performance mainly because it is provided with improved horizontal resolution. Finally, we find that implementing the state-of-the-art TUW-VMF3 ZHD product for GPS-PWV retrieval yields no statistically significant errors, even under extreme weather conditions, and the retrieved GPS-PWVs can well characterize the PWV diurnal variations in all seasons except winter. Additionally, considering the fact that the operational and forecasted TUW-VMF3 ZHDs present almost equivalent performance, this article is also beneficial to real-time GPS-PWV retrieval using forecasted TUW-VMF3 ZHDs, thus allowing for the ease of real-time GPS-PWV retrieval.
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关键词
Global Positioning System,Delays,Surfaces,Global navigation satellite system,Data models,Spatial resolution,Real-time systems,Global positioning system (GPS),precipitable water vapor (PWV),zenith hydrostatic delay (ZHD),ZHD height adjustment
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