A New Model to Improve Gravity Models

Abstract The continental water storage is significantly in-fluenced by wetlands, which are highly affected by climate change and anthropogenic influences. The Pantanal, located in the Paraguay river basin, is one of the world’s largest and most important wetlands because of the environmental biodiversity that represents. The satellite gravity mission GRACE (Gravity Recovery And Climate Experiment) provided until 2017 time-variable Earth’s gravity field models that reflected the variations due to mass transport processes-like continental water storage changes-which allowed to study environments such as wetlands, at large spatial scales. The water storage variations for the period 2002-2016, by using monthly land water mass grids of Total Water Storage (TWS) derived from GRACE solutions, were evaluated in the Pantanal area. The capability of the GRACE mission for monitoring this particular environment is analyzed, and the comparison of the water mass changes with rainfall and hydrometric heights data at different stations distributed over the Pantanal region was carried out. Additionally, the correlation between the TWS and river gauge measurements, and the phase differences for these variables, were also evaluated. Results show two distinct zones: high correlations and low phase shifts at the north, and smaller correlation values and consequently significant phase differences towards the south. This situation is mainly related to the hydrogeological domains of the area.

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A new f(R) gravity model and properties of gravitational waves in it

The European Physical Journal C ◽

10.1140/epjc/s10052-020-08684-3 ◽

2020 ◽

Vol 80 (12) ◽

Author(s):

Dhruba Jyoti Gogoi ◽

Umananda Dev Goswami

Keyword(s):

Gravitational Waves ◽

Gravity Model ◽

Longitudinal Mode ◽

Mass Scale ◽

Gravity Models ◽

Jordan Frame ◽

New Model ◽

Existing Problems ◽

Pulsar Timing ◽

New Directions

AbstractIn this paper, we have introduced a new f(R) gravity model as an attempt to have a model with more parametric control, so that the model can be used to explain the existing problems as well as to explore new directions in physics of gravity, by properly constraining it with recent observational data. Here basic aim is to study the properties of Gravitational Waves (GWs) in this new model. In f(R) gravity metric formalism, the model shows the existence of scalar degree of freedom as like other f(R) gravity models. Due to this reason, there is a scalar mode of polarization of GWs present in the theory. This polarization mode exists in a mixed state, of which one is transverse massless breathing mode with non-vanishing trace and the other is massive longitudinal mode. The longitudinal mode being massive, travels at speed less than the usual tensor modes found in General Relativity (GR). Moreover, for a better understanding of the model, we have studied the potential and mass of scalar graviton in both Jordan frame and Einstein frame. This model can pass the solar system tests and can explain primordial and present dark energy. Also, we have put constraints on the model. It is found that the correlation function for the third mode of polarization under certain mass scale predicted by the model agrees well with the recent data of Pulsar Timing Arrays. It seems that this new model would be useful in dealing with different existing issues in the areas of astrophysics and cosmology.

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Multiple-data-based monthly geopotential model set LDCmgm90

Scientific Data ◽

10.1038/s41597-019-0239-7 ◽

2019 ◽

Vol 6 (1) ◽

Cited By ~ 3

Author(s):

Wei Chen ◽

Jiesi Luo ◽

Jim Ray ◽

Nan Yu ◽

Jian Cheng Li

Keyword(s):

Gravity Data ◽

Gravity Models ◽

Geopotential Model ◽

Satellite Mission ◽

Stripe Pattern ◽

Angular Momenta ◽

Multiple Data ◽

Model Set ◽

Gravity Recovery

Abstract While the GRACE (Gravity Recovery and Climate Experiment) satellite mission is of great significance in understanding various branches of Earth sciences, the quality of GRACE monthly products can be unsatisfactory due to strong longitudinal stripe-pattern errors and other flaws. Based on corrected GRACE Mascon (mass concentration) gridded mass transport time series and updated LDCgam (Least Difference Combination global angular momenta) data, we present a new set of monthly gravity models called LDCmgm90, in the form of Stokes coefficients with order and degree both up to 90. The LDCgam inputs are developed by assimilating degree-2 Stokes coefficients from various versions of GRACE (including Mascon products) and SLR (Satellite Laser Ranging) monthly gravity data into combinations of outputs from various global atmospheric, oceanic, and hydrological circulation models, under the constraints of accurately measured Earth orientation parameters in the Least Difference Combination (LDC) scheme. Taking advantages of the relative strengths of the various input solutions, the LDCmgm90 is free of stripes and some other flaws of classical GRACE products.

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Introducing an Improved GRACE Global Point-Mass Solution—A Case Study in Antarctica

Remote Sensing ◽

10.3390/rs12193197 ◽

2020 ◽

Vol 12 (19) ◽

pp. 3197 ◽

Cited By ~ 1

Author(s):

Vagner G. Ferreira ◽

Bin Yong ◽

Kurt Seitz ◽

Bernhard Heck ◽

Thomas Grombein

Keyword(s):

Noise Level ◽

Order Approximation ◽

Statistical Tests ◽

Taylor Series Expansion ◽

Point Mass ◽

Surface Integral ◽

Goddard Space Flight Center ◽

Gravity Recovery ◽

Grace Mission ◽

Level 2

In the so-called point-mass modeling, surface densities are represented by point masses, providing only an approximated solution of the surface integral for the gravitational potential. Here, we propose a refinement for the point-mass modeling based on Taylor series expansion in which the zeroth-order approximation is equivalent to the point-mass solution. Simulations show that adding higher-order terms neglected in the point-mass modeling reduces the error of inverted mass changes of up to 90% on global and Antarctica scales. The method provides an alternative to the processing of the Level-2 data from the Gravity Recovery and Climate Experiment (GRACE) mission. While the evaluation of the surface densities based on improved point-mass modeling using ITSG-Grace2018 Level-2 data as observations reveals noise level of approximately 5.77 mm, this figure is 5.02, 6.05, and 5.81 mm for Center for Space Research (CSR), Goddard Space Flight Center (GSFC), and Jet Propulsion Laboratory (JPL) mascon solutions, respectively. Statistical tests demonstrate that the four solutions are not significant different (95% confidence) over Antarctica Ice Sheet (AIS), despite the slight differences seen in the noises. Therefore, the estimated noise level for the four solutions indicates the quality of GRACE mass changes over AIS. Overall, AIS shows a mass loss of −7.58 mm/year during 2003–2015 based on the improved point-mass solution, which agrees with the values derived from mascon solutions.

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Comparing and evaluating GRACE and GRACE-FO mascon data in the study of polar motion excitation

10.5194/gstm2020-8 ◽

2020 ◽

Author(s):

Justyna Śliwińska ◽

Małgorzata Wińska ◽

Jolanta Nastula

Keyword(s):

Polar Motion ◽

Temporal Variations ◽

Great Success ◽

Spectral Bands ◽

The Earth ◽

Hydrological Angular Momentum ◽

High Consistency ◽

Gravity Recovery ◽

Grace Mission ◽

Polar Motion Excitation

The Gravity Recovery and Climate Experiment (GRACE) mission has provided global observations of temporal variations in mass redistribution at the surface and within the Earth for the period 2002&#8211;2017. Such measurements are commonly exploited to interpret polar motion changes due to variations in the Earth&#8217;s surficial fluids, especially in the continental hydrosphere. Such impacts are usually examined by computing the so-called hydrological polar motion excitation (Hydrological Angular Momentum, HAM). The great success of the GRACE mission and the scientific robustness of its data contributed to the launch of its successor, GRACE Follow-On (GRACE-FO), which begun in May 2018 and continues to the present. This study compares the estimates of HAM computed from GRACE and GRACE-FO mascon data provided by three data centers: Jet Propulsion Laboratory (JPL), Center for Space Research (CSR), and Goddard Space Flight Center (GSFC). The analysis of HAM is performed for different spectral bands. A validation of different HAM estimates is conducted here using precise geodetic measurements of the pole coordinates and geophysical models (so-called geodetic residuals or GAO). Comparison of HAM computed from different mascon data sources indicates high consistency between the solutions provided by JPL and CSR, and low consistency between the GSFC solution and other data. The reason for this may be that the strategy used for GSFC mascons computation is different than methodology exploited by CSR and JPL teams. This study also indicates that HAM computed using CSR and JPL solutions are characterized by the highest consistency with GAO in all considered spectral bands.

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Time-variations of equivalent water heights'from Grace Mission and in-situ river stages in the Amazon basin

Acta Amazonica ◽

10.1590/s0044-59672012000100015 ◽

2012 ◽

Vol 42 (1) ◽

pp. 125-134 ◽

Cited By ~ 6

Author(s):

Flavio Guilherme Vaz de Almeida ◽

Stephane Calmant ◽

Frédérique Seyler ◽

Guillaume Ramillien ◽

Denizar Blitzkow ◽

...

Keyword(s):

Time Series ◽

Amazon Basin ◽

Temporal Variations ◽

Regression Coefficients ◽

Linear Relationships ◽

Time Variations ◽

Gravity Recovery ◽

Grace Mission

Gravity Recovery and Climate Experiment (GRACE) mission is dedicated to measuring temporal variations of the Earth's gravity field. In this study, the Stokes coefficients made available by Groupe de Recherche en Géodésie Spatiale (GRGS) at a 10-day interval were converted into equivalent water height (EWH) for a ~4-year period in the Amazon basin (from July-2002 to May-2006). The seasonal amplitudes of EWH signal are the largest on the surface of Earth and reach ~ 1250mm at that basin's center. Error budget represents ~130 mm of EWH, including formal errors on Stokes coefficient, leakage errors (12 ~ 21 mm) and spectrum truncation (10 ~ 15 mm). Comparison between in situ river level time series measured at 233 ground-based hydrometric stations (HS) in the Amazon basin and vertically-integrated EWH derived from GRACE is carried out in this paper. Although EWH and HS measure different water bodies, in most of the cases a high correlation (up to ~80%) is detected between the HS series and EWH series at the same site. This correlation allows adjusting linear relationships between in situ and GRACE-based series for the major tributaries of the Amazon river. The regression coefficients decrease from up to down stream along the rivers reaching the theoretical value 1 at the Amazon's mouth in the Atlantic Ocean. The variation of the regression coefficients versus the distance from estuary is analysed for the largest rivers in the basin. In a second step, a classification of the proportionality between in situ and GRACE time-series is proposed.

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Preliminary GRACE-FO gravity field solutions from Tongji University

10.5194/egusphere-egu2020-7707 ◽

2020 ◽

Author(s):

Qiujie Chen ◽

Yunzhong Shen ◽

Xingfu Zhang ◽

Jürgen Kusche

Keyword(s):

Mass Transport ◽

Gravity Field ◽

Sampling Rate ◽

Laser Ranging ◽

University Of Technology ◽

Gravity Field Determination ◽

New Feature ◽

Gravity Recovery ◽

Grace Mission ◽

Tongji University

Due to the battery issue, the Gravity Recovery and Climate Experiment (GRACE) mission unfortunately came to an end in October 2017 after providing more than 15 years of mass transport information of our changing planet. To continue to monitoring the mass transport in the Earth system, the GRACE Follow-On (GRACE-FO) was launched in May 2018. As a new feature of GRACE-FO, a Laser Ranging Interferometer (LRI) was equipped to measure the inter-satellite range at a nanometer level. Since May 2019, GRACE-FO Level-1B observations have been made available to our community. Using the GRACE-FO Level-1B observations without laser ranging information, preliminary GRACE-FO gravity field solutions from Center for Space Research (CSR), GeoForschungsZentrum (GFZ), Jet Propulsion Laboratory (JPL) and Graz University of Technology have been released. Incorporating laser ranging observations into gravity field determination, a preliminary time series of GRACE-FO gravity field solutions has been derived from Tongji University in collaboration with University of Bonn. In this paper, the signal and noise of our gravity field solutions are analyzed and compared to those from other research groups. Our results show that the laser ranging observations with a sampling rate of 2s are able to improve gravity field solutions by about 7% in terms of geoid degree variances up to degree and order 96 as compared to the K-Band ranging data with a sampling rate of 5s.

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Antarctic Ice Mass Change Products from GRACE/GRACE-FO Using Tailored Sensitivity Kernels

Remote Sensing ◽

10.3390/rs13091736 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1736

Author(s):

Andreas Groh ◽

Martin Horwath

Keyword(s):

Regional Integration ◽

Synthetic Data ◽

Mass Change ◽

Data Sets ◽

Optimization Approach ◽

External Data ◽

Error Covariance ◽

Gravity Recovery ◽

The Antarctic ◽

Grace Mission

We derived gravimetric mass change products, i.e., gridded and basin-averaged mass changes, for the Antarctic Ice Sheet (AIS) from time-variable gravity-field solutions acquired by the Gravity Recovery and Climate Experiment (GRACE) mission and its successor GRACE-FO, covering more than 18 years. For this purpose, tailored sensitivity kernels (TSKs) were generated for the application in a regional integration approach. The TSKs were inferred in a formal optimization approach minimizing the sum of both propagated mission errors and leakage errors. We accounted for mission errors by means of an empirical error covariance model, while assumptions on signal variances of potential sources of leakage were used to minimize leakage errors. To identify the optimal parameters to be used in the TSK generation, we assessed a set of TSKs by quantifying signal leakage from the processing of synthetic data and by inferring the noise level of the derived basin products. The finally selected TSKs were used to calculate mass change products from GRACE/GRACE-FO Level-2 spherical harmonic solutions covering 2002-04 to 2020-07. These products were compared to external data sets from satellite altimetry and the input–output method. For the period under investigation, the mass balance of the AIS was quantified to be −90.9±43.5 Gt a−1, corresponding to a mean sea-level rise of 0.25±0.12 mm a−1.

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Continental Water Storage Changes Sensed by GRACE Satellite Gravimetry

10.5772/intechopen.96109 ◽

2021 ◽

Author(s):

Guillaume Ramillien ◽

Lucía Seoane

Keyword(s):

Water Mass ◽

Water Storage ◽

Satellite System ◽

Geoid Height ◽

Continental Hydrology ◽

Grace Satellite Gravimetry ◽

Grace Satellites ◽

Time Variations ◽

Gravity Recovery ◽

Grace Mission

Since its launch in March 2002, the Gravity Recovery And Climate Experiment (GRACE) mission has been mapping the time variations of the Earth’s gravity field with a precision of 2–3 cm in terms of geoid height at the surface resolution of 300–400 km. The unprecedented precision of this twin satellite system enables to detect tiny changes of gravity that are due to the water mass variations inside the fluid envelops of our planet. Once they are corrected from known gravitational contributions of the atmosphere and the oceans, the monthly and (bi)weekly GRACE solutions reveal the continental water storage redistributions, and mainly the dominant seasonal cycle in the largest drainage river basins such as Amazon, Congo, Mississippi. The potential differences measured between the twin GRACE satellites represent the sum of integrated surface waters (lakes and rivers), soil moisture, snow, ice and groundwater. Once they are inverted for estimating surface water mass densities, GRACE solutions are also used to establish the long-term mass balance of the ice sheets impacted by global warming, for quantifying the interannual variations of the major aquifers, as well as for surveying the hydrological signatures of intense meteorological events lasting a few days such as tropical hurricanes. This chapter describes GRACE gravity products and the different data processings used for mapping continental water storage variations, it also presents the most remarkable results concerning global continental hydrology and climate changes.

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A novel method for cold-region streamflow hydrograph separation using GRACE satellite observations

Hydrology and Earth System Sciences ◽

10.5194/hess-25-2649-2021 ◽

2021 ◽

Vol 25 (5) ◽

pp. 2649-2662

Author(s):

Shusen Wang ◽

Junhua Li ◽

Hazen A. J. Russell

Keyword(s):

Water Resources ◽

Climate Models ◽

Hydrograph Separation ◽

Snowmelt Runoff ◽

New Model ◽

Arbitrary Choice ◽

Physically Based ◽

Novel Method ◽

Gravity Recovery ◽

Watershed Size

Abstract. Streamflow hydrograph analysis has long been used for separating streamflow into baseflow and surface runoff components, providing critical information for studies in hydrology, climate and water resources. Issues with established methods include the lack of physics and arbitrary choice of separation parameters, problems in identifying snowmelt runoff, and limitations on watershed size and hydrogeological conditions. In this study, a Gravity Recovery and Climate Experiment (GRACE)-based model was developed to address these weaknesses and improve hydrograph separation. The model is physically based and requires no arbitrary choice of parameters. The new model was compared with six hydrograph separation methods provided with the U.S. Geological Survey Groundwater Toolbox. The results demonstrated improved estimates by the new model particularly in filtering out the bias of snowmelt runoff in baseflow estimate. This new model is specifically suitable for applications over large watersheds which is complementary to the traditional methods that are limited by watershed size. The output from the model also includes estimates for watershed hydraulic conductivity and drainable water storage, which are useful parameters in evaluating aquifer properties, calibrating and validating hydrological and climate models, and assessing regional water resources.

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