International Geodesy Association(IAG) workshop on HydroGeodesy and 3rd Satellite Gravity and Hydrology forum were held in Wuhan from June 29th to 30th. This conference was hosted by the International Geodesy Association and State Key Laboratory of Geodesy and Earth’s Dynamics (SKLGED), Institute of Geodesy and Geophysics, Chinese Academy of Sciences(IGG,CAS). Co-organized by Wuhan University, Huazhong University of Science and Technology, Institute of Seismology of China Earthquake Administration and China University of Geosciences (Wuhan). Theoretical frontiers, interdisciplinary intersections, industry dynamics and technical applications in the fields of satellite geodesy, hydrology, hydrogeology, cryospheric science and hydrological remote sensing,etc. There have nearly 200 experts and scholars conducted extensive and in-depth discussions and exchanges from countries such as China, the United States, Germany, France, Singapore, Australia and Japan. The conference was supported by the National Natural Science Foundation of China and the National Science and Technology Infrastructure for Precision Gravity Measurement.
The theme of the forum was hydrogeodesy and satellite gravity and Hydrology. In recent years, the rapid development of satellite geodesy has greatly promoted the application of modern geodetic surveying techniques in hydrology, oceanography and cryosphere science. The series of gravity satellite programs represented by GRACE satellite have deepened the understanding of the temporal and spatial changes of terrestrial water reserves in the global and regional areas. Geodetic observation technology represented by GNSS and InSAR can obtain the information of surface hydrological load deformation with high spatial and temporal resolution. Satellite altimetry technology provides change information about the height of sea level, rivers and lakes. This conference aims to discuss the latest scientific research progress in global and regional hydrological cycle and material balance with multi-source and spatio-temporal resolution.
The opening ceremony of the conference was held on the morning of June 29. Wang Yong, vice Director and researcher of IGG, CAS, delivered an opening speech. The opening ceremony was presided over by researcher Zhong Min and associate researcher Feng Wei. At the meeting, Xu Houze, a fellow of the Chinese Academy of Sciences and a researcher at IGG,CAS, introduced China's latest research advances in the field of satellite gravity. China has made a breakthrough in the fields of gravity satellite platform, load development, data processing and scientific application. Satellite gravity observation data has been successfully applied to the monitoring of temporal and spatial changes of terrestrial water and groundwater reserves in China, and the loss of groundwater in North China and the loss of quality caused by melting of Tianshan glaciers have been detected. In view of the current insufficient spatial resolution of gravity satellites, relevant experts at home and abroad have proposed a next-generation gravity satellite plan based on laser ranging, which is expected to greatly improve the space-time resolution of gravity satellite observations and promote the application of gravity satellites in hydrology.
Xia Jun, an academician of the Chinese Academy of Sciences and the professor of Wuhan University, introduced the water safety problem and the application of Earth observation in water resources management in China. He said that due to environmental changes and human activities, the impact of China's water security problems are severe, and the water ecosystems still face greater pressure. Under the background of global climate change, the frequency and intensity of drought and flood disasters in southern China have increased. In recent years, the rapid development of earth remote sensing technology, including satellite geodesy, has provided important observational data for China's water resources management and effective use, and has important reference value.
Bridget Scanlon, an NAE(National Academy of Engineering) member and a researcher of the University of Texas, introduced the progress of satellite gravity monitoring and hydrological model simulation for changes in terrestrial water reserves. The latest research finds that global hydrological models often underestimate the signal intensity of seasonal and long-term trends in terrestrial water reserves, while satellite gravity observations are more reliable. Gravity satellite monitoring has found that global terrestrial water reserves have increased about 80 billion tons per year for nearly a decade.
Dennis Lettenmaier, an NAE member and a professor at the University of California at Los Angeles, introduced the development of satellite remote sensing technology for different components of land water and different elements of the water cycle. In particular, the SWOT wide-range altimetry satellite, which plan to launch in 2021, is expected to be a geodetic satellite of the new synthetic aperture radar model, which will measure the surface water body with high precision and estimate river runoff variation. It is of great significance for dynamic monitoring of floods and monitoring of changes in water reserves.
Shi Jiancheng, the National “Thousand Talents Program” special expert and the director of the State Key Laboratory of Remote Sensing Science of the Institute of Remote Sensing and Digital Earth, CAS, said that the “Water Circle Observation Mission，WCOM” will be launched in China’s 13th Five-Year Plan in the report. WCOM is the first remote sensing satellite in the world to comprehensively observe the global water cycle, including key elements of land, ocean and atmosphere. As the chief scientist of the satellite program, professor Shi said that the WCOM project is China's first space earth science satellite program for major scientific frontier issues, and is expected to further enhance human understanding of the temporal and spatial distribution characteristics and changes of the water circle in the context of global change. It will play an important role in the fields of water resources management and utilization, flood control and drought resistance, and agricultural production in China.
Professor Jurgen Kusche of the University of Bonn, Germany, presented the latest research progress of GRACE and GRACE Follow On in the field of global and regional drought monitoring. Prof. Jurgen said that it can greatly improve the spatial resolution of gravity satellite observations and provide tens of kilometers of resolution of land water reserve variation signals by combining hydrological models and data assimiltion techniques. GRACE gravity satellites have been successfully applied to drought monitoring in countries and regions such as Europe, the United States and Australia. These latest research advances have important reference value for the drought monitoring research of gravity satellites in China.
CK Shum, a Ohio State University professor and a “Thousand Talents Program” expert in IGG, CAS, his latest research shows that the GRACE gravity satellite can successfully monitor the high-frequency signals of quality changes caused by the snowstorm in 2008 and the flood in 2010 in the south of China. This has important reference significance for improving the early warning capability of flood disasters in the future.
Xie Zhenghui, deputy director and researcher of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, reported the progress of data assimilation which joint gravity satellite observations and hydrological models. Using the latest data assimilation methods, gravity satellite observations provide effective constraints on hydrological parameters and improve the ability of hydrological models to simulate and predict for terrestrial and groundwater reserves.
Chen Jianli, a researcher at the Space Research Center at the University of Texas at Austin, presented the latest developments in global and regional sea level changes which joint satellite altimetry, satellite gravity and oceanographic data, and introduced the latest developments in the GRACE Follow On satellite launched in May 2018.
In addition to the special invitation report, the conference has 4 thematic reports, such as “Geogeometric Monitoring of Groundwater Variation”, “Remote Sensing Monitoring of Rainfall, Evapotranspiration and Runoff”, “Multi-Source Geodetic Observations and Glacier Quality Variation” and “Satellite geodesy and hydrological remote sensing”. Young researchers from more than 60 institutions at home and abroad made special oral reports and posters.
As the first international hydroGeodesy forum, during the two-day forum, the participants carried out extensive and in-depth academic exchanges and discussions around the theme of the conference, promoting the intersection of modern geodesy and hydrology. The forum provided a platform for young scholars to exchanges and achieved a complete success.
Institute of Geodesy and Geophysics. Chinese Academy of Sciences
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