Challenge 30- Real-Time Modeling of Hydrological Loading Deformation and Gravity Changes

[RubenRT7]

Challenge 30 - Real-Time Modeling of Hydrological Loading Deformation and Gravity Changes

Stream 3 - Software Development for Earth Sciences applications

Goal

The overall goal of this project is to establish a platform for hydrological loading deformation and gravity changes, which geodesists and geophysicists can use to:

1. Correct real-time geodetic time series.
2. Monitor changes in the shape and gravity of the Earth at a continental scale to identify regions of rapid subsidence and uplift during wet and dry seasons, respectively.

Mentors and skills

• Mentors:
• University of Bonn: Makan A. Karegar, Anne Springer, Christina Strohmenger, Bernd Uebbing
• ECMWF: Jasper Denissen
• Skills required:
  • Background in geodesy, geophysics, mathematics, physics, computer sciences or related fields.
  • Experience with Python or C++, visualization software (e.g., QGIS, GMT), GRIB and/or netCDF files.
  • Basic time series analysis knowledge.

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Challenge description

General problem:
Hydrological loading is the distribution of water in its various forms across the Earth's surface, causing elastic deformation of the solid Earth and fluctuations in the gravity field. For geodetic studies of other Earth processes such as tectonic, volcanic and flooding-induced deformation as well as associated gravity changes, hydrological loading serves as a source of systematic error, requiring accurate determination. Data from the Extremes Digital Twin (EDT), supported by the Destination Earth (DestinE) programme of the European Commission, can provide high-resolution near real-time components of continental water storage, including surface water (soil moisture, rivers, and lakes) and snow equivalent water. The elastic response of the Earth's crust to these surface load distributions can be estimated through spatial convolution of elastic Green's functions with a surface mass loading field. However, the current knowledge gap lies in real-time modeling of surface deformation and gravity changes. The real-time modeling of hydrological deformation can be especially useful for correcting geodetic observations such as Global Navigation Satellite System (GNSS), gravimeters, tilt and strain meters for early warning for natural hazards. Changes in the Earth's surface and gravity could indicate potential natural hazards such as earthquakes, volcanic eruptions, landslides and tsunamis. Furthermore, such real-time modeling assists in assessing the stability of infrastructure such as bridges, dams, pipelines and buildings during critical events like coastal and river flooding, allowing for timely maintenance and risk management measures. This information helps engineers and policymakers make informed decisions regarding construction, maintenance, and land-use planning. Additionally, continuous monitoring provides valuable data to better understand the underlying hydrological processes causing surface deformation and gravity changes. Finally, such initiatives may allow for further collaboration among geo-scientists, researchers, and policymakers.

Expected results or solution:
The outcome of this challenge will be 3-hourly to hourly variations in three-dimensional Earth surface deformation and gravity changes associated with continental water redistribution. Such a high-resolution model of deformation and gravity fluctuations allows for the improvement in detecting sudden changes in geodetic time series for natural hazard monitoring.

Possible strategies to solve the problem:
The solution is based on the spherical harmonic approach. This approach requires as input the spherical harmonic coefficients of forcing data and the load Love numbers. The load Love numbers describe the deformation of the Earth under the action of a unit surface point mass through the three dimensionless load Love numbers for a spherical non-rotating elastic layered Earth model (Wang et al. 2012). A set of high-degree load Love numbers for the Preliminary Reference Earth Model (PREM, Dziewonski and Anderson, 1981) produced in the center-of-earth (CE) frame will be used.

The global forcing data is first converted to spherical harmonic coefficients using spherical harmonic analysis. Then, these spherical harmonic coefficients will be combined with elastic load Love numbers to estimate surface deformation and gravity changes through spherical harmonic synthesis. Potential challenges include implementing an algorithm that is time-efficient while maintaining accuracy.

The validation of the solution will include both internal and external assessments. Internally, it will be based on a checkerboard test while externally, selected GNSS time series distributed globally will be used together with in-situ gravity data collected in Todenfeld (Germany) along with GFZ's hydrological loading dataset (HYDL).