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Wei You
Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China

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Accepted manuscript
Published: 19 July 2021 in Geophysical Journal International
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Summary The Gravity Recovery and Climate Experiment (GRACE) mission has been providing abundant information regarding the mass changes of the Earth in terms of time series of temporal gravity field models since 2002. To derive temporal gravity field models with high accuracy, many methods have been developed. In this paper, we focus on the variational equation integration approach. The main works can be summarized as follows: (1) analyzing the quality of GRACE Level1B RL02 and RL03 data, including accelerometer observations (ACC1B), star camera measurements (SCA1B) and K-Band low-low Satellite-to-Satellite Tracking (SST) range-rate (KBRR) data (KBR1B); (2) discussing the influence of arc-specific parameters and arc length on gravity field recovery; and (3) comparing two different methods used for sensitivity matrix generation, namely, a numerical integration method and the method of variation of constants, from the perspectives of accuracy and efficiency, respectively. Based on these analyses, discussions and comparisons, a new time series of GRACE monthly gravity field models in terms of spherical harmonic coefficients completed to degree and order 60, called SWJTU-GRACE-RL02p, was derived by using the modified variational equation integration approach bashed on GRACE Level1B RL03 data, covering the period from April 2002 to October 2011 with some gaps in between due to poor quality or missing GRACE data. Thus we are looking at the results some 10yrs in the past. The differences between the traditional variational equation integration approach and the approach that we used are mainly as follows: (1) according to the GRACE data quality, the arc length is no longer a constant in the determination of temporal gravity field models; (2) the kinematic empirical parameters, which are mainly designed to remove the bias and drifts in KBRR residuals, are abandoned; and (3) the method of variation of constants developed at the Astronomical Institute of the University of Bern (AIUB) and used to solve the system of variational equations associated with constrained pulses and piecewise constant accelerations is used to calculate the sensitivity matrices of accelerometer bias parameters to improve the calculation efficiency and ensure the calculation accuracy. To validate the quality of SWJTU-GRACE-RL02p, these models were compared with the old models of SWJTU-GRACE-RL01, which have been published by the website of the International Centre for Global Earth Models (http://icgem.gfz-potsdam.de/series), and the official products (i.e. the RL05 and RL06 versions of GRACE LEVEL2 at the Centre for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoForschungsZentrum (GFZ)). Compared to the RL06 version of official models, the models of SWJTU-GRACE-RL02p present competitive performance for global mass changes. Furthermore, these models show less noise and a higher signal strength over some local areas with large mass changes than the models of SWJTU-GRACE-RL01. The comparisons between SWJTU-GRACE-RL02p and a variety of other models including official models, GLDAS, models provided by EGSIEM and daily solutions released by ITSG indicate that our approach and the data processing details presented in this paper provide an alternative strategy for the recovery of temporal gravity field models from GRACE-type data.

ACS Style

Biao Yu; Wei You; Dong-Ming Fan; Yong Su; Zemede M Nigatu. A comparison of GRACE temporal gravity field models recovered with different processing details. Geophysical Journal International 2021, 1 .

AMA Style

Biao Yu, Wei You, Dong-Ming Fan, Yong Su, Zemede M Nigatu. A comparison of GRACE temporal gravity field models recovered with different processing details. Geophysical Journal International. 2021; ():1.

Chicago/Turabian Style

Biao Yu; Wei You; Dong-Ming Fan; Yong Su; Zemede M Nigatu. 2021. "A comparison of GRACE temporal gravity field models recovered with different processing details." Geophysical Journal International , no. : 1.

Journal article
Published: 11 February 2021 in Remote Sensing
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Hydroclimatic extremes such as droughts and floods triggered by human-induced climate change are causing severe damage in the Nile River Basin (NRB). These hydroclimatic extremes are not well studied in a holistic approach in NRB. In this study, the Gravity Recovery and Climate Experiment (GRACE) mission and its Follow on mission (GRACE-FO) derived indices and other standardized hydroclimatic indices are computed for developing monitoring and evaluation methods of flood and drought. We evaluated extreme hydroclimatic conditions by using GRACE/GRACE-FO derived indices such as water storage deficits Index (WSDI); and standardized hydroclimatic indices (i.e., Palmer Drought Severity Index (PDSI) and others). This study showed that during 1950–2019, eight major floods and ten droughts events were identified based on standardized-indices and GRACE/GRACE-FO-derived indices. Standardized-indices mostly underestimated the drought and flood severity level compared to GRACE/GRACE-FO derived indices. Among standardized indices PDSI show highest correlation (r2 = 0.72) with WSDI. GRACE-/GRACE-FO-derived indices can capture all major flood and drought events; hence, it may be an ideal substitute for data-scarce hydro-meteorological sites. Therefore, the proposed framework can serve as a useful tool for flood and drought monitoring and a better understanding of extreme hydroclimatic conditions in NRB and other similar climatic regions.

ACS Style

Zemede Nigatu; Dongming Fan; Wei You; Assefa Melesse. Hydroclimatic Extremes Evaluation Using GRACE/GRACE-FO and Multidecadal Climatic Variables over the Nile River Basin. Remote Sensing 2021, 13, 651 .

AMA Style

Zemede Nigatu, Dongming Fan, Wei You, Assefa Melesse. Hydroclimatic Extremes Evaluation Using GRACE/GRACE-FO and Multidecadal Climatic Variables over the Nile River Basin. Remote Sensing. 2021; 13 (4):651.

Chicago/Turabian Style

Zemede Nigatu; Dongming Fan; Wei You; Assefa Melesse. 2021. "Hydroclimatic Extremes Evaluation Using GRACE/GRACE-FO and Multidecadal Climatic Variables over the Nile River Basin." Remote Sensing 13, no. 4: 651.

Journal article
Published: 11 January 2021 in Advances in Space Research
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The Nile River Basin (NRB) is facing extreme demand for its water resources due to an alarming increase in population and the changing climate. The NRB is not compatible with ground-based in-situ observations owing to its large basin area size and limited hydrological data access from basin countries. Thus, it lends itself to remotely sensed approaches with high spatial resolution and extended temporal coverage. The Gravity Recovery and Climate Experiment (GRACE) avails a unique opportunity to investigate the changes in key components of terrestrial water storage (TWS). GRACE TWS solutions have specific tuning parameters and processing strategies that result in regionally specific variations and error patterns. We explored the TWS time series spatiotemporal changes, trends, uncertainties, and signal-to-noise ratio among different GRACE TWS data. We had also investigated the key terrestrial water storage components such as surface water, soil moisture, and groundwater storage changes. The results show that GRACE spherical harmonic solutions' uncertainty is higher than the mass concentration (mascon) over the NRB, and the Center for Space Research-mascons had the best performance. The evapotranspiration correlation (R2 = 0.85) has the highest correlation with GRACE’s TWS, whereas the normalized difference vegetation index (R2 = 0.82) has the second highest correlation. Notably, significant long-term (2003–2017) negative groundwater and soil moisture trends demonstrate a potential depletion of the NRB. Despite an increase in precipitation and the TWS time series, the rate of decline increased rapidly after 2008, thereby indicating the possibility of human-induced change (e.g. for irrigation purposes). Therefore, the results of this study provide a guide for future studies related to hydro-climatic change over the NRB and similar basins.

ACS Style

Zemede M. Nigatu; Dongming Fan; Wei You. GRACE products and land surface models for estimating the changes in key water storage components in the Nile River Basin. Advances in Space Research 2021, 67, 1896 -1913.

AMA Style

Zemede M. Nigatu, Dongming Fan, Wei You. GRACE products and land surface models for estimating the changes in key water storage components in the Nile River Basin. Advances in Space Research. 2021; 67 (6):1896-1913.

Chicago/Turabian Style

Zemede M. Nigatu; Dongming Fan; Wei You. 2021. "GRACE products and land surface models for estimating the changes in key water storage components in the Nile River Basin." Advances in Space Research 67, no. 6: 1896-1913.

Journal article
Published: 31 October 2020 in Remote Sensing
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The Gravity Recovery and Climate Experiment (GRACE) data have been extensively used to evaluate the total terrestrial water storage anomalies (TWSA) from hydrological models. However, which individual water storage components (i.e., soil moisture storage anomalies (SMSA) or groundwater water storage anomalies (GWSA)) cause the discrepancies in TWSA between GRACE and hydrological models have not been thoroughly investigated or quantified. In this study, we applied GRACE mass concentration block (mascon) solutions to evaluate the spatio-temporal TWSA trends (2003–2014) from seven prevailing hydrological models (i.e., Noah-3.6, Catchment Land Surface Model (CLSM-F2.5), Variable Infiltration Capacity macroscale model (VIC-4.1.2), Water—Global Assessment and Prognosis (WaterGAP-2.2d), PCRaster Global Water Balance (PCR-GLOBWB-2), Community Land Model (CLM-4.5), and Australian Water Resources Assessment Landscape model (AWRA-L v6)) in Australia and, more importantly, identified which individual water storage components lead to the differences in TWSA trends between GRACE and hydrological models. The results showed that all of the hydrological models employed in this study, except for CLM-4.5 model, underestimated the GRACE-derived TWSA trends. These underestimations can be divided into three categories: (1) ignoring GWSA, e.g., Noah-3.6 and VIC-4.1.2 models; (2) underrating both SMSA and GWSA, e.g., CLSM-F2.5, WaterGAP-2.2d, and PCR-GLOBWB-2 models; (3) deficiently modeling GWSA, e.g., AWRA-L v6 model. In comparison, CLM-4.5 model yielded the best agreement with GRACE but overstated the GRACE-derived TWSA trends due to the overestimation of GWSA. Our results underscore that GRACE mascon solutions can be used as a valuable and efficient validation dataset to evaluate the spatio-temporal performance of hydrological models. Confirming which individual water storage components result in the discrepancies in TWSA between GRACE and hydrological models can better assist in further hydrological model development.

ACS Style

Xinchun Yang; Siyuan Tian; Wei Feng; Jiangjun Ran; Wei You; Zhongshan Jiang; Xiaoying Gong. Spatio-Temporal Evaluation of Water Storage Trends from Hydrological Models over Australia Using GRACE Mascon Solutions. Remote Sensing 2020, 12, 3578 .

AMA Style

Xinchun Yang, Siyuan Tian, Wei Feng, Jiangjun Ran, Wei You, Zhongshan Jiang, Xiaoying Gong. Spatio-Temporal Evaluation of Water Storage Trends from Hydrological Models over Australia Using GRACE Mascon Solutions. Remote Sensing. 2020; 12 (21):3578.

Chicago/Turabian Style

Xinchun Yang; Siyuan Tian; Wei Feng; Jiangjun Ran; Wei You; Zhongshan Jiang; Xiaoying Gong. 2020. "Spatio-Temporal Evaluation of Water Storage Trends from Hydrological Models over Australia Using GRACE Mascon Solutions." Remote Sensing 12, no. 21: 3578.

Preprint content
Published: 16 June 2020
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The Nile River Basin (NRB) is facing extreme pressure on its water resources due to an alarmingly increasing population that is extremely vulnerable in aspects of irrigation and hydropower. The NRB ascends itself to remotely sensed approaches with high resolution of spatial and temporal coverage as disparate to ground-based in-situ observations due to its size and limited access from basin countries. The Gravity Recovery and Climate Experiment (GRACE) allow a unique opportunity to investigate the changes in key components of Terrestrial Water Storage (TWS). Differences in tuning parameters and processing strategies result in GRACE TWS solutions with regionally specific variations and error patterns. We explored the spatiotemporal changes of the TWS time series, trend, uncertainties, and signal-to-noise ratio (SNR) among different GRACE TWS. We had also investigated the key terrestrial water storage components (surface water, soil moisture, and groundwater storage changes). The results show that the uncertainty of GRACE spherical harmonic (SH) solutions are higher than the mass concentration (mascon) over the NRB, and the Center for Space Research-mascons (CSR-M) noted the first best performance. Substantially, significant long-term (2003–2017) negative groundwater and soil moisture trend demonstrates a potential depletion over NRB. Despite an increase in precipitation and TWS time series, the rate of decline noted to increase rapidly from 2008, thus indicating the possibility of human-induced change ( e.g., for irrigation purposes). Thus, the result of this study provides a guiding principle for future studies in TWS change-related hydro-climatic change over NRB and similar basins.

ACS Style

Zemede M. Nigatu; Dongming Fan; Wei You. Integrating GRACE products and land surface models to estimate changes in key components of terrestrial water storage in the Nile River Basin. 2020, 1 .

AMA Style

Zemede M. Nigatu, Dongming Fan, Wei You. Integrating GRACE products and land surface models to estimate changes in key components of terrestrial water storage in the Nile River Basin. . 2020; ():1.

Chicago/Turabian Style

Zemede M. Nigatu; Dongming Fan; Wei You. 2020. "Integrating GRACE products and land surface models to estimate changes in key components of terrestrial water storage in the Nile River Basin." , no. : 1.

Article
Published: 28 July 2017 in Geophysical Research Letters
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Eleven GPS crustal vertical displacement (CVD) solutions for 110 IGS08/IGS14 core stations provided by the International Global Navigation Satellite Systems Service Analysis Centers are compared with seven Gravity Recovery and Climate Experiment (GRACE)-modeled CVD solutions. The results of the internal comparison of the GPS solutions from multiple institutions imply large uncertainty in the GPS postprocessing. There is also evidence that GRACE solutions from both different institutions and different processing approaches (mascon and traditional spherical harmonic coefficients) show similar results, suggesting that GRACE can provide CVD results of good internal consistency. When the uncertainty of the GPS data is accounted for, the GRACE data can explain as much as 50% of the actual signals and more than 80% of the GPS annual signals. Our study strongly indicates that GRACE data have great potential to correct the nontidal loading in GPS time series.

ACS Style

Yanchao Gu; Dongming Fan; Wei You. Comparison of observed and modeled seasonal crustal vertical displacements derived from multi-institution GPS and GRACE solutions. Geophysical Research Letters 2017, 44, 7219 -7227.

AMA Style

Yanchao Gu, Dongming Fan, Wei You. Comparison of observed and modeled seasonal crustal vertical displacements derived from multi-institution GPS and GRACE solutions. Geophysical Research Letters. 2017; 44 (14):7219-7227.

Chicago/Turabian Style

Yanchao Gu; Dongming Fan; Wei You. 2017. "Comparison of observed and modeled seasonal crustal vertical displacements derived from multi-institution GPS and GRACE solutions." Geophysical Research Letters 44, no. 14: 7219-7227.

Journal article
Published: 01 January 2017 in Advances in Space Research
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ACS Style

Yanchao Gu; Linguo Yuan; Dongming Fan; Wei You; Yong Su. Seasonal crustal vertical deformation induced by environmental mass loading in mainland China derived from GPS, GRACE and surface loading models. Advances in Space Research 2017, 59, 88 -102.

AMA Style

Yanchao Gu, Linguo Yuan, Dongming Fan, Wei You, Yong Su. Seasonal crustal vertical deformation induced by environmental mass loading in mainland China derived from GPS, GRACE and surface loading models. Advances in Space Research. 2017; 59 (1):88-102.

Chicago/Turabian Style

Yanchao Gu; Linguo Yuan; Dongming Fan; Wei You; Yong Su. 2017. "Seasonal crustal vertical deformation induced by environmental mass loading in mainland China derived from GPS, GRACE and surface loading models." Advances in Space Research 59, no. 1: 88-102.