For the past three decades, it has been possible to measure the earth's static gravity from satellites. Such measurements have been used to address many important scientific problems, including the earth's internal structure, and geologically slow processes like mantle convection. In principle, it is possible to resolve the time-varying component of the gravity field by improving the accuracy of satellite gravity measurements.
These temporal variations are caused by dynamic processes that change the mass distribution in the earth, oceans, and atmosphere. Acquisition of improved time-varying gravity data would open a new class of important scientific problems to analysis, including crustal motions associated with earthquakes and changes in groundwater levels, ice dynamics, sea-level changes, and atmospheric and oceanic circulation patterns.
This book evaluates the potential for using satellite technologies to measure the time-varying component of the gravity field and assess the utility of these data for addressing problems of interest to the earth sciences, natural hazards, and resource communities.
- SATELLITE GRAVITY AND THE GEOSPHERE
- Copyright
- Preface
- Contents
- Satellite Gravity and the Geosphere
- Executive Summary
- BENEFITS OF A DEDICATED SATELLITE GRAVITY MISSION
- MISSION SCENARIOS AND MEASUREMENT TECHNIQUES
- OCEAN DYNAMICS AND HEAT FLUX
- SOLID EARTH PROCESSES
- WATER CYCLING
- SEA-LEVEL RISE AND GLACIOLOGY
- THE DYNAMIC ATMOSPHERE
- A TOOL FOR SCIENCE
- 1 Introduction
- SCIENTIFIC OVERVIEW
- THE ATMOSPHERE AS A POTENTIAL SOURCE OF NOISE FOR TIME-DEPENDENT APPLICATIONS
- HISTORY OF SATELLITE GRAVITY
- "GRAVITY" AS USED IN THIS REPORT
- ORGANIZATION OF REPORT
- 2 Mission Scenarios and Measurement Techniques
- SATELLITE OBSERVATIONS OF THE GRAVITY FIELD
- TRADE-OFFS IN SPACECRAFT MISSION DESIGN
- MISSION SCENARIOS
- GPS
- SST and SSI
- SGG and SGGE
- PREVIOUS STUDIES
- ERROR ESTIMATES FOR MISSION SCENARIOS OF THIS REPORT
- Degree Amplitude Error Spectra
- Precision Versus Resolution
- STANDARD GENERIC MISSIONS
- CONCLUSIONS
- 3 The Gravity Field as a Tool For Science
- REFERENCE FRAME (1): THE FOUNDATION FOR MEASURING THE CHANGING EARTH
- REFERENCE FRAME (2): THE GEOID, FLUID CIRCULATION, AND SATELLITEALTIMETRY
- DATA CALIBRATION AND VERIFICATION: GIVING OLD DATA NEW VALUE
- CONCLUSIONS
- 4 Ocean Dynamics and Heat Flux
- STATIC FIELD
- TIME-DEPENDENT MEASUREMENTS
- Bottom Pressure and Mass
- Steric Changes
- Accuracy
- CONCLUSIONS
- 5 Solid Earth Processes
- MANTLE CONVECTION AND PLUMES: UNDERSTANDING THE EARTH'S HEAT ENGINE
- POST-GLACIAL REBOUND
- REGIONAL DEFORMATION AND STRUCTURE: THE SURFACE MANIFESTATION OF PLATE TECTONICS
- EARTHQUAKES
- CONCLUSIONS
- 6 Water Cycling
- WATER TRANSFER TO THE ATMOSPHERE
- SOIL MOISTURE INVENTORY
- GRAVITY AND THE GEWEX CONTINENTAL-SCALE INTERNATIONAL PROJECT
- SNOWLOAD AND ASSOCIATED RUNOFF
- AQUIFERS
- CONCLUSIONS
- 7 Sea-Level Change
- THERMAL EXPANSION OF THE OCEANS
- ICE MASS BALANCE
- Contributions from the Greenland and Antarctic Ice Sheets
- Isostatic Rebound
- Snow-Accumulation Rates
- Atmospheric Pressure
- Complementarity with Satellite Laser Altimetry
- Drainage Systems Within Ice Sheets
- Contributions from Glaciers
- CONCLUSIONS
- 8 The Dynamic Atmosphere: Unraveling the Contributions of the Earth's Subsystems
- 9 Conclusions
- Afterword
- Appendix A Spherical Harmonics: Degree Variances, Wavelengths, Upward Continuation, Anomalous Potentials, Signal and Error…
- A.1 SPHERICAL HARMONIC EXPANSIONS OF GRAVITATIONAL POTENTIALS
- A.2 DEGREE VARIANCES
- A.3 WAVELENGTH RELATED TO HARMONIC DEGREE
- A.4 ATTENUATION WITH ALTITUDE
- A.5 ANOMALOUS POTENTIALS AND "KAULA'S RULE"
- A.6 DEGREE AMPLITUDE SPECTRA
- A.7 ERRORS IN OBSERVABLES RELATED TO ERRORS IN THE GRAVITY FIELD
- A.8 ACCURACY VERSUS RESOLUTION IN GAUSSIAN-WEIGHTED AVERAGES OVER A SPHERICAL CAP
- Appendix B Modeling
- RATIONALE
- CALCULATIONS
- SPECIFIC APPLICATIONS
- Acronyms
- References
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