Xiaogong Hu
Chinese Academy of Sciences
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Featured researches published by Xiaogong Hu.
Geophysical Research Letters | 2003
Jianli Chen; Clark R. Wilson; Xiaogong Hu; Byron D. Tapley
[1]xa0A recent study of satellite laser ranging measurements by Cox and Chao [2002] indicates that large-scale mass redistribution has caused a rapid change in Earths dynamic oblateness (J2) since 1998. Using satellite altimeter observations and two runs of an ocean general circulation models (OGCM), we examine mass variations in the oceans and their estimated effect on J2. Combined altimeter and OGCM results indicate variations similar to the J2 changes in 1998, and predict considerably larger oceanic effects on the J2 anomaly than purely OGCM estimates, suggesting that the oceans should not be ruled out by any means as a significant source of this interesting geodetic anomaly, until they have been studied further.
Surveys in Geophysics | 2018
Shengnan Ni; Jianli Chen; Clark R. Wilson; Jin Li; Xiaogong Hu; Rong Fu
Improved data quality of extended record of the Gravity Recovery and Climate Experiment (GRACE) satellite gravity solutions enables better understanding of terrestrial water storage (TWS) variations. Connections of TWS and climate change are critical to investigate regional and global water cycles. In this study, we provide a comprehensive analysis of global connections between interannual TWS changes and El Niño Southern Oscillation (ENSO) events, using multiple sources of data, including GRACE measurements, land surface model (LSM) predictions and precipitation observations. We use cross-correlation and coherence spectrum analysis to examine global connections between interannual TWS changes and the Niño 3.4 index, and select four river basins (Amazon, Orinoco, Colorado, and Lena) for more detailed analysis. The results indicate that interannual TWS changes are strongly correlated with ENSO over much of the globe, with maximum cross-correlation coefficients up to ~0.70, well above the 95% significance level (~0.29) derived by the Monte Carlo experiments. The strongest correlations are found in tropical and subtropical regions, especially in the Amazon, Orinoco, and La Plata basins. While both GRACE and LSM TWS estimates show reasonably good correlations with ENSO and generally consistent spatial correlation patterns, notably higher correlations are found between GRACE TWS and ENSO. The existence of significant correlations in middle–high latitudes shows the large-scale impact of ENSO on the global water cycle.
Remote Sensing | 2017
Shengnan Ni; Jianli Chen; Clark R. Wilson; Xiaogong Hu
Satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) provides a quantitative measure of terrestrial water storage (TWS) change at different temporal and spatial scales. In this study, we investigate the ability of GRACE to quantitatively monitor long-term hydrological characteristics over the Lake Volta region. Principal component analysis (PCA) is employed to study temporal and spatial variability of long-term TWS changes. Long-term Lake Volta water storage change appears to be the dominant long-term TWS change signal in the Volta basin. GRACE-derived TWS changes and precipitation variations compiled by the Global Precipitation Climatology Centre (GPCC) are related both temporally and spatially, but spatial leakage attenuates the magnitude of GRACE estimates, especially at small regional scales. Using constrained forward modeling, we successfully remove leakage error in GRACE estimates. After this leakage correction, GRACE-derived Lake Volta water storage changes agree remarkably well with independent estimates from satellite altimetry at interannual and longer time scales. This demonstrates the value of GRACE estimates to monitor and quantify water storage changes in lakes, especially in relatively small regions with complicated topography.
Journal of Geophysical Research | 2017
Jin Li; Jianli Chen; Ziang Li; Song-Yun Wang; Xiaogong Hu
The Earths shape is much closer to an ellipsoid than a sphere. The commonly used spherical approximation in mass change inversion is expected to cause bias by the spherical harmonic (SH) solutions from Gravity Recovery and Climate Experiment (GRACE), especially in high-latitude regions where significant present-day ice losses occur. This bias, or ellipsoidal correction, reaches up to 8% from the evaluation by simulations based on synthetic mass change rate models. Further evaluation using 14 plus years of GRACE monthly SH solutions (from April 2002 to December 2016) indicates that the ellipsoidal correction is also noticeable in the total mass change time series over polar regions. Before and after the ellipsoidal correction, the estimated linear rates from mass change time series differ by 4.3%, 4.7%, 5.2%, 5.7% and 6.6% for five selected regions over Greenland, Antarctic Peninsula (AP), Amundsen Sea Embayment (ASE), Alaska glacier, and Svalbard Islands, respectively. Although with amplitudes likely below the current GRACEs uncertainty level, these differences are consistently negative over the five regions. This indicates that the spherical approximation leads to systematic underestimation for polar mass change rates. Thus the ellipsoidal correction needs to be considered for more precise mass recovery with GRACE SH solutions. It also depends on spatial scales of mass change signals (the smaller the spatial scale, the larger the correction). To more reliably estimate high-latitude surface mass changes by GRACE SH solutions, the ellipsoidal correction is recommended, especially for ice-loss signals over polar regions.
Geophysical Journal International | 2007
Xiaogong Hu; Lixiang Liu; B. Ducarme; Houze Xu; H.-P. Sun
Annals of Geophysics | 2016
Song-Yun Wang; Jianli Chen; Jin Li; Xiaogong Hu; Shengnan Ni
Geophysical Journal International | 2018
Song-Yun Wang; J. L. Chen; Clark R. Wilson; Jin Li; Xiaogong Hu
Geophysical Journal International | 2018
Xiaogong Hu
Geodesy and Geodynamics | 2018
Jin Li; Jianli Chen; Shengnan Ni; Lu Tang; Xiaogong Hu
Journal of Geophysical Research | 2017
Jin Li; Jianli Chen; Ziang Li; Song-Yun Wang; Xiaogong Hu