1. GOCE User Workshop 2014, 28.11.2014, Paris R. Pail, R. Bingham, C. Braitenberg, A. Eicker, M. Horwath, L. Longuevergne, I. Panet, C. Rolstad-Denby, B. Wouters … and international science teams TU München, Institute of Astronomical and Physical Geodesy Consolidated science and user requirements for a next generation gravity field mission

2. GOCE User Workshop 2014, 28.11.2014, Paris Contents  Motivation of this initiative  Overall set-up  Main objectives  Science and User Requirement Document  Theme-specific requirements  Preliminary consolidation results

3. GOCE User Workshop 2014, 28.11.2014, Paris CHAMP GRACE GOCE GRACE-FO 2000 2005 20102015 2020 2025 Motivation: Gravity field mission infrastructure ?

4. GOCE User Workshop 2014, 28.11.2014, Paris Motivation  Several future gravity field studies (national, international) have resulted in quite different performance numbers as a target for a future gravity mission (2025+)  consolidation under the boundary condition of the technical feasibility required  Strong interest in a future gravity field mission (beyond GRACE FO) must be expressed by the user communities.

5. GOCE User Workshop 2014, 28.11.2014, Paris Motivation International activity initiated by GGOS Satellite Mission Working Group (SMWG) IAG SC 2.3: Dedicated Satellite Gravity Missions IAG SC 2.6: Gravity and Mass Displacements under the umbrella of IUGG and consultation by Space Agencies with the special focus on „Consolidation of Science and User Requirements“ documented in a Science and User Requirement Document.

6. GOCE User Workshop 2014, 28.11.2014, Paris Overall set-up Preparation: 2013-2014 Workshop in Herrsching, 26-27/09/2014 Target: January 2015

7. GOCE User Workshop 2014, 28.11.2014, Paris Sciences themes & teams Theme CoordinatorsIUGG assoc. Hydrology A. EickerIAHS L. Longuevergne Cryosphere M. HorwathIACS C. Rolstad-Denby Ocean B. WoutersIAPSO R. Bingham Solid Earth I. PanetIASPEI C. Braitenberg  Each team is composed of ~15–20 international scientists.  Aspects of atmosphere are implicitly covered by these teams.

8. GOCE User Workshop 2014, 28.11.2014, Paris Overall set-up Preparation: 2013-2014 Workshop in Herrsching, 26-27/09/2014 Target: January 2015

9. GOCE User Workshop 2014, 28.11.2014, Paris Performance table: reference scenarios Increased temp. res.

10. GOCE User Workshop 2014, 28.11.2014, Paris Objectives:  Coming to a consolidated view on the science and user requirements within the international user community, represented by the TSGs (decoupled from mission requirements or technical feasibility).  Identification of research fields that could not be tackled by current gravity missions.  Evaluation of the added value (qualitatively and quantitatively) of these scenarios with respect to science return.  In addition to pure science objectives, also practical applications, services shall be considered (“science for society”). Objectives & output of this initiative Output: 1.Consolidated Science and User Requirement Document (SRD) 2.Expression of need by user community, e.g., by IUGG resolution

11. GOCE User Workshop 2014, 28.11.2014, Paris SRD – Contents (draft) 1.Summary for decision-makers 2.Introduction and logic of the document 3.Overarching scientific questions and contributions by satellite gravimetry 4.Requirements of 4 main thematic fields  Scientific questions and challenges and their relation to gravity field signals  Relevant temporal and spatial scales (bubble plots)  Achievements and limitations of current gravity missions  Identification of potential new satellite gravimetry application fields  Added value of individual mission scenarios  Definition of theme-specific science requirements 5.Cross-theme aspects and additional thematic fields 6.Applications (“Science for Society”) 7.Consolidated Science Requirements

12. GOCE User Workshop 2014, 28.11.2014, Paris Hydrology: Scientific and societal requirements 14 scientific questions  Water storage in medium to small subbasins  Closing the atmospheric water balance  12 others mostly related to Hydrological processes understanding Improving model predictability 4 societal questions  Water management  Coping for extremes / early warning / risk management  Climate change  Services

13. GOCE User Workshop 2014, 28.11.2014, Paris Cryosphere applications 1 Cryosphere mass balance at monthly to decadal time scales to understand climate forcing on ice sheets, glaciers and ice caps 3 cm @ 150km 2 Cryosphere contribution to global and regional sea level 3 cm @ 150km 3 Observe and separate GIA as a prerequisite to understand feedback between ice mass change and regional sea level 0.3 cm/yr @ 150 km 4 Determination of mass changes of individual ice sheet drainage basins (aid modeling and prediction) 3 cm @ 150km1 m @ 25km (monthly) 5 Aid ice sheet modeling and prediction by observing processes leading to ice flow dynamics changes (including grounding line migration, subglacial and supraglacial hydrology) 1 m @ 25km (weekly) 6 Aid atmospheric modeling by observing processes related to SMB changes 3 cm @ 150km1 m @ 25km (weekly) 7 Determination of mass changes of mountain glacier systems and ice caps 3 cm @ 150km 8 Observation of glacier and ice caps processes for hydrological and disaster mitigation applications (flooding, water storage, hydro power) 3 cm @ 150km1 m @ 10 km (weekly) Target Wishful thinking

14. GOCE User Workshop 2014, 28.11.2014, Paris Cryosphere requirements vs. mission scenarios

15. GOCE User Workshop 2014, 28.11.2014, Paris Ocean: science and societal requirements Minimum requirement: Continuation of GRACE/GRACE-FO time series with increased spatial resolution Global and regional sea level change Estimating ocean heat content uptake (particularly deep) Better understanding of large-scale processes: e.g. ENSO, MOC, AMO Initialization and constraint of ocean and climate models Mean – 1 cm at d/o 200 MDT assimilation for operational ocean forecasting Ambitious requirement: 1 cm monthly at d/o 200 Monitoring Atlantic meridional over-turning circulation (MOC) Dynamics of coastal sea level variability and boundary processes Dynamics of the Southern Ocean – transport, identification/tracking of ACC fronts Estimation of barotropic component of ocean circulation

16. GOCE User Workshop 2014, 28.11.2014, Paris Solid Earth: main research objectives 1. Seismic cycle: M w 7 earthquakes – Emphasis on subduction zones, undersea events – M w 7: highly destructive – follow aftershocks sequence? 2. Glacial Isostatic Adjustment – Needed for assessing ice mass balance, sea level budget – Identify low viscosity zones 3. Continental geodynamics and tectonic motions – Mountain building, oceanic ridges uplift 4. Underground fluids and their interaction with the solid Earth – Water, oil and minerals extraction – Induced seismicity Studying these topics requires to develop a global geodynamic model of the Earth, also including mantle and maybe core processes. Societal benefits: natural hazards, climate change, natural resources management

17. GOCE User Workshop 2014, 28.11.2014, Paris Preliminary Results: Consolidated Science and User Requirements Threshold scenario Monthly: d/o 50 (400 km): 5 mm / 0.5 mm/yr e.w.h. d/o 100 (200 km): 10 cm / 1 cm/yr e.w.h. Daily: d/o 50: 50 mm e.w.h. In combination with GRACE & GRACE-FO more reliable estimates of trends Improved spatial resolution Improved temporal resolution: reduction of aliasing Target scenario Monthly: d/o 50 (400 km): 0.5 mm / 0.05 mm/yr e.w.h. d/o 100 (200 km): 1 cm / 0.1 cm/yr e.w.h. Daily: d/o 50: 5 mm e.w.h. Significant leap forward Significantly increased spatial and temporal resolution New applications (science, societal benefit)

18. GOCE User Workshop 2014, 28.11.2014, Paris Bubble plots At least 3 parameters (would require 3D-plot): Spatial resolution Temporal resolution Accuracy → We decided to plot Accuracy over Spatial resolution for different time-scales  instantaneous – short-term  seasonal – inter-annual  long-term – trends → Checking target signal properties against mission scenarios

19. GOCE User Workshop 2014, 28.11.2014, Paris Continental Hydrology Surface water storage changes Snow water equivalent changes Ground water storage changes Soil moisture storage Surface water storage changes Ground water storage changes Ice sheet SMB variations Glaciers & ice caps Ice flow dynamics Ice sheet SMB variations Ice flow dynamics Glaciers & ice caps GIA Cryosphere Bubble plots (preliminary, example) Seasonal to inter-annual signal Long-term signal (trends)

20. GOCE User Workshop 2014, 28.11.2014, Paris Added value: hydrology (example) Histogram of basis sizes of hydrological catchments

21. GOCE User Workshop 2014, 28.11.2014, Paris Cross-theme aspects  Atmosphere atmosphere models are currently limiting factor interacting loop: gravity – atmospheric modelling  Sea level Impact by all 4 themes Coastal sea level (societal benefit)  GIA Impact by all 4 themes Important for correct ice and water mass balance, loading → Closing the global mass balance

22. GOCE User Workshop 2014, 28.11.2014, Paris Practical applications with societal benefit → Near real-time !

23. GOCE User Workshop 2014, 28.11.2014, Paris Outlook  SRD planned to be ready by January 2015  Preparation of IUGG resolution  Publication of main contents of SRD Your contribution to this initiative is very welcome. If you are interested, please contact us!