Recent progresses and future prospectives of ground-based GNSS water vapor sounding

Water vapor is one of the most important parameters that can be used to investigate extreme weather events and climatic phenomena. Effective monitoring and analyses of the water vapor content are of great significance for forecasting various types of meteorological disaster events and analyses of climatic changes. Ground-based GNSS, as a relatively newly emerged atmospheric sounding technique, has been widely applied to the sounding of atmospheric water vapor. The performance of the ground-based GNSS water vapor sounding technique has experienced unprecedented developments with the substantial strengthened richness of multi-frequency and multi-mode as well as its global operation ability and wide-spread ground-based infrastructures. All these offer strong data support and a great opportunity to advance our knowledge and an in-depth understanding of climate change and extreme weather events. The primary purpose of this paper is to synthesize and to review the current status and developments of the ground-based GNSS water vapor sounding technique. First, recent primary progresses and significant achievements in the retrieval of various types of atmospheric parameters using the ground-based GNSS technique are comprehensively summarized. Then, the theory, technical feature and major advancement of the GNSS-derived atmospheric products in the applications of climate analyses and extreme weather forecasting are presented. Finally, the challenges, opportunities and future prospectives in terms of the technique and its innovative applications of national and international significance are provided.