Acta Geodaetica et Cartographica Sinica ›› 2025, Vol. 54 ›› Issue (10): 1757-1768.doi: 10.11947/j.AGCS.2025.20250129

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A composite drought index derived from a combination of GNSS PWV/vertical deformation and GRACE/GRACE-FO data

Chaolong YAO1,2,3(), Hongrui YOU1, Xuanhui HE1, Junya LU1, Yiqian XIE1, Qiong LI2,4(), Shuang ZHU5, Zhicai LUO2,6   

  1. 1.College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China
    2.National Precise Gravity Measurement Facility, Huazhong University of Science and Technology, Wuhan 430074, China
    3.Guangdong Province Land Information Engineering Technology Research Center, South China Agricultural University, Guangzhou 510642, China
    4.School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu 610500, China
    5.School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
    6.National Gravitation Laboratory, Huazhong University of Science and Technology, Wuhan 430074, China
  • Received:2025-03-24 Revised:2025-10-18 Online:2025-11-14 Published:2025-11-14
  • Contact: Qiong LI E-mail:clyao@scau.edu.cn;qiongli@swpu.edu.cn
  • About author:YAO Chaolong (1986—), male, PhD, associate professor, majors in hydrological, meteorological and drought geodesy. E-mail: clyao@scau.edu.cn
  • Supported by:
    The National Natural Science Foundation of China(42474045);The National Center for Precision Gravity Measurement Science Open Subject(PGMF-2024-Q003)

Abstract:

Developing a composite drought index (CDI) by combining multiple drought related variables is crucial for comprehensively and accurately assessing drought conditions. In this study, based on the global navigation satellite system (GNSS) precipitable water vapor (PWV)/vertical deformation and Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) satellite gravimetric data spanning from 2011 to 2022, we developed a novel hydro-meteorological CDI in southwestern China through a data fusion model combining robust estimation and joint distribution function (Copula function). The data fusion model was built to reduce the impacts of the possible outliers and considering the complex response relationship between meteorological and hydrological droughts. The results showed that ① The meteorological drought index constructed from GNSS PWV and precipitation data had good consistency with precipitation anomalies and the standardized precipitation evapotranspiration index (SPEI), with correlation coefficients of 0.88 and 0.73, respectively; ② The methods of Helmert robust variance estimation based on the IGGⅢ and robust principle component analysis (RPCA) can effectively overcome the impact of outliers and improve the accuracy of data fusion, but the overall precision of Helmert robust variance estimation was better than that of RPCA; ③ The Copula-based CDI constructed in our study contains information on atmospheric water vapor, precipitation, and terrestrial water storage, which can effectively reflect the evolution process of meteorological and hydrological droughts simultaneously. The research results provide a new way for expanding and deepening the interdisciplinary research and applications of GNSS meteorology and hydro-geodesy in comprehensive drought monitoring.

Key words: GNSS PWV/vertical deformation, satellite gravimetry, robust estimation, Copula function, composite drought index

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