Gy. Tóth | 2024-09-25

August/Septermber 2024


General Announcement

  • Call for IAG proposals for the IUGG Support Program of Scientific Meetings in 2025

Meeting Announcement

  • Geodesy for Africa at the UNGA79

Meetings Calendar

IAG Sponsored Meetings

  • GGOS Topical Meeting on the Atmosphere
  • GGOS Days 2024
  • IAG Workshop on Asia Pacific Gravity, Geoid, and Vertical Datums
  • SIRGAS 2024 Symposium
  • 6th Joint International Symposium on Deformation Monitoring (JISDM)
  • IAG Scientific Assembly 2025

Geodesy Related Meetings

  • ESA 9th International Colloquium on Scientific and Fundamental Aspects of GNSS 2024
  • Geodesy for Africa at the UNGA79
  • GRACE/GRACE-FO Science Team Meeting 2024
  • 2025 Glacial Isostatic Adjustment workshop: Advancing Models and Observational Constraints
  • IAU Symposium 401: Advancing Reference Systems, Ephemeris, and Standards

Reports

  • Technical workshop on the assimilation of GRACE and GRACE-FO data into hydrological models



General Announcements


Call for IAG proposals for the IUGG Support Program of Scientific Meetings in 2025

We would like to draw your attention to opportunities of support/sponsorship from the IUGG for selected scientific meetings (e.g., workshops, advanced schools, symposia) planned in 2025. 

The call for proposals is open, refer to: https://iugg.org/meetings/guidlines-for-meetings-support/ 

If you wish to propose a meeting via IAG, please contact the IAG Secretary General – IAG-Office(at)bkg.bund.de − and submit your request until 8th of October 2024. There will be an IAG-internal reviewing process with a decision by end of October.

Proposed scientific meetings for the IUGG Support Program must:

  • Have a well-defined, scientifically relevant and actual topic in the fields of geodesy/geophysics;
  • Have scientific merit and a balanced scope w.r.t. IUGG associations i.e. preference will be given to multi- and trans-disciplinary meetings;
  • be internationally oriented;
  • be inclusive in view of countries/regions, gender and career stage of the participants.

Your request to IAG must specify all entries listed below:

  • Name of meeting, venue and dates
  • Primary sponsors and other known co-sponsors
  • Name and address of the Chair of the Local Organizing Committee
  • Meeting website
  • Scientific objective and scope of the meeting
  • Estimated number of participants, abstracts, and sessions
  • Level of support requested (in US$) and explanation of how the money will be used
  • Additional information as appropriate

Thank you in advance for your interest and kind cooperation!


IAG Bureau


Meeting Announcements


Geodesy for Africa at the UNGA79

In addressing global challenges like climate change, urbanization, and sustainable resource management, accurate geodetic data is crucial. We aim to elevate the global geodesy supply chain, align geodetic science with  policymaking, and advance research through multidisciplinary cooperation. Central to our agenda is integrating the African perspective to address unique challenges and contributions. This meeting focuses on advancing UN Resolution 69/22, “A Global Geodetic Reference Frame (#GGRF) for Sustainable Development,” fostering discussions among Member States, international organizations, and geospatial experts. One of the key topics to be discussed the 1st Joint Development Plan for Global Geodesy, aiming to accelerate progress towards the UN Sustainable Development Goals. Find more at https://sciencesummitunga.com/science-summit-unga79/ 


Laura Sanchez


Meetings Calendar

IAG Sponsored Meetings

Geodesy Related Meetings

Further details are available in the IAG Event Calendar at: http://www.iag-aig.org/events


Report


Technical workshop on the assimilation of GRACE and GRACE-FO data into hydrological models

During a virtual event on 18 and 19 January 2024, 13 scientists from various groups (NASA Goddard, Universities Bonn, Stuttgart, Aalborg, Newcastle, Asian Institute of Technology) presented recent progress and challenges ahead in the assimilation (DA) of GRACE/-FO TWSA data into land surface and hydrology models. The online workshop was designed to identify technical issues, open questions and challenges in methodology, implementation and evaluation, and a potential path towards standard procedures for GRACE/-FO DA. The workshop was timely since space agencies and institutions prepare for the data processing of the foreseen GRACE-C and NGGM missions.


Open issues that were identified include

  1. Modeling 
    • Limited dynamic range in simulating e.g. groundwater variability may limit the possible impact of GRACE DA
    • Model calibration needed / possible with GRACE data?
  2. GRACE data
    • Data assimilation with monthly GRACE data cannot deal well with short-term snow variability
    • Assimilating GRACE data can degrade model output in cases where the data exhibits leakage of a fine scale signal (e.g., mountain snowpack) over a larger area.
    • Does it make sense/are there ways to downscale TWSA before DA?
    • Which corrections need to be applied to the GRACE data (earthquakes, lakes, …)?
    • What GRACE filtering method is most appropriate? Pros/cons of mascon vs grids from SHC solutions
  3. Data assimilation techniques
    • Nonlinear processes (e.g baseflow) and resulting non-Gaussian pdfs
    • Perturbation approaches – forcing vs. state vs. parameter perturbation
    • Depending on the model, which storages should be updated and which not
    • Optimality of model and observation error choices
    • Realism/representativeness of GRACE/-FO error covariance matrices and derived error covariance representations
    • Numerical issues, stability and possible relation to error and state covariance
    • Using coarse-scale GRACE data and applying a filter without accounting for spatial correlation at the finer model resolution inevitably causes a poor distribution of water over regions with strong variation in water storage: Filtering with accounting for spatial correlation is needed with spatial aggregation of model forecasts to the observation resolution.
    • Applying the increment at the beginning or end of the month, or spread over the month?
    • Assimilating daily GRACE products shows promise
    • It is valuable to relocate the effects of lakes and reservoirs during GRACE DA
    • Multivariate assimilation can produce improved results through enforcement of multiple con-straints on the water cycle.
  4. Validation
    • Validation data, e.g. for groundwater well data, are not all publicly available which makes com-parison across different studies difficult. Same for specific yield maps.

General recommendations across presentations / from several colleagues

  • Develop ways of including daily spherical harmonic or swath-type GRACE/-FO TWSA solutions into DA frameworks (temporal vs. spatial resolution tradeoff)
  • Develop ways of taking into account GRACE/-FO error correlation
  • Ensemble-DA seems the preferred method. EnKS appears superior to EnKF
  • Localization filtering seems beneficial
  • Develop a way for preprocessing/accounting for mass change effects in GRACE/-FO that are un-accounted for in models (e.g. seasonal/long-term glacier mass, large Earthquakes)
  • Bayesian merging for GRACE downscaling, using copula’s, might be a possibility
  • Assimilating range observations instead of TWSA solutions?
  • Find self-correcting scale-factors to downscale GRACE data during DA?
  • Potential of multi-sensor & multi-variate DA, incl. GRACE DA.
  • Can anything be learned from ML to extend the GRACE dataset?
  • Can we agree on a „benchmark validation data set“?

Jürgen Kusche, Matt Rodell, Gabrielle deLannoy, Anne Springer




The IAG Newsletter is under the editorial responsibility of the Communication and Outreach Branch (COB) of the IAG. It is an open forum and contributors are welcome to send material (preferably in electronic form) to the IAG COB (newsletter@iag-aig.org). These contributions should complement information sent by IAG officials or by IAG symposia organizers (reports and announcements). The IAG Newsletter is published monthly. It is available in different formats from the IAG new internet site: http://www.iag-aig.org.

Each IAG Newsletter includes several of the following topics:

  1. news from the Bureau Members   
  2. general information
  3. reports of IAG symposia
  4. reports by commissions, special commissions or study groups
  5. symposia announcements
  6. book reviews
  7. fast bibliography

DOCUMENTS
IAG_Newsletter_August_September_2024.pdf

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