iggIGCP565 and AfricaArray Workshop
Standard and non-standard GRACE products forhydrology
Jürgen Kusche(1), Ehsan Forootan(1), Annette Eicker(1), Enrico Kurtenbach(1),Anno Löcher(1), Petra Döll(2), Frank Flechtner(3)
(1) University of Bonn, (2) University of Frankfurt, (3) GFZ Potsdam
SPP 1257 “Mass Transport and Mass Distribution”
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• GRACE status• GRACE science results• GRACE standard products & how to use them• GRACE non-standard products & procedures• Beyond GRACE
SPP1257 „Mass Transport and Mass Distribution in the System Earth“is supported by Germany‘s national funding agency DFG
Outline
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GRACE Mission Facts
• highly successful US/German twin-satellite mission launched in 2002, to monitor mass transport and mass distribution in system Earth
• PI: Byron Tapley (University of Texas, Center for Space Research), Co-PI: Dr. Frank Flechtner (GFZ Potsdam)
• Will celebrate 10th birthday on March 17, 2012• Will likely end its operation in the next 1-3 years (depending on
battery status and solar activity)
GRACE Status
April 2011:2700 users registered at GFZ/ISDC (16% from Germany/China/USA each)
700+ publications (many Nature/Science)
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GRACE has initiated interdisciplinary research between hydrologists, glaciologists, oceanographers, geophysicists, geodesists.
Major breakthroughs in the understanding of – changes in the terrestrial water cycle (water storage, exchange and
depletion),– melting and growing of glaciers, Greenland and Antarctic ice sheets, – sea level rise and what contributes to it (mass or volume change), – and solid Earth (past glaciation and deglaciation, Earthquakes)
DFG SPP1257 „Mass Transport and Mass Distribution in the System Earth“
– Largest interdisciplinary research program (~50PhD positions for 6 years)
– www.massentransporte.de– AGU Fall Meeting: session G11 "Mass transport in the Earth system"
GRACE Status
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GRACE Mission Facts
GRACE Status
Generation of GRACE Standard L1a/b Products (Flechtner 9/11)
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GRACE Health Status• Degraded battery capacity (cell failure)• Every 161 days (Sun in orbital plane), battery use is limited (
maximize lifetime)• http://www.csr.utexas.edu/grace/operations/mission_status/
GRACE Status
GRACE SDS Newsletter 9/2011: Level-2 gravity field determination
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Sea Level – decomposing sea level rise into mass and steric change
GRACE Science Results
GSLR: altimetry = GRACE + Argo + deep ocean warming (Leuliette and Willis 2011, Oceanography)
- using GRACE L2 standard products + postprocessing -
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Polar Ice Sheets and Glaciers
GRACE Science Results
Shrinking at
increasing speed
Shrinking at
decreasing speed
Schrama and Wouters (2011, JGR): -201Gt/y
Ewert et al(acc., J Geodyn)-191Gt/y
Greenland ice mass loss and sea level contribution (~0.5mm/a)
- using GRACE L2 standard products + postprocessing -
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Solid Earth – Constraining seismic and fault models for large EQs
GRACE Science Results
Han et al. (2010, GRL): GRACE observes coseismic gravity effect of the M8.8 2010 Chile EQ
- using non-standard products -
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Solid Earth – Constraining seismic and fault models for large EQs
GRACE Science Results
Cambiotti et al. (2011, JGR): GRACE helps constraining seismic models of the 2004 Sumatra EQ
- using standard L2 products + postprocessing (DDK3 decorrelation) -
GRACE co-seismic PREM with ocean layer, two seismic source models
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Hydrology –Grippa et al. (2011): TWS from 6 GRACE solutions, different post-processing, and 9 LSMs- multimodel averaging is difficult to justify -
GRACE Science Results
GRACE
LSM
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Hydrology – Henry et al. (2011):GRACE TWS – GLDAS Soil moisure = Groundwater variation
GRACE Science Results
Avg. GW
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Hydrology – Becker et al. (2010,C.R. Geoscience)
GRACE Science Results
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GRACE standard products• L2 level: Monthly spherical harmonic expansions of gravity potential
V
User interest (I)• „L3 level“: Monthly maps of equivalent water heights (can be derived
from L2 standard products)
User interest (II)• Enhance temporal and/or spatial resolution• Minimize leakage of mass variation outside area of interest• Combine with in-situ data
Nonstandard products– Special L1-L2 processing approaches – Development of postprocessing
GRACE Data Products
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Solid Earth Response(Love numbers/ Geophysical model)
Monthly sets of spherical harmonics. TWS from GRACE
Issues• SH resolution• Latency and gaps• Processing• AOD-Products• Degree-1 and C20
EWH maps
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Monthly sets of spherical harmonics
• SH resolution – from a user point of view, desirable resolution depends on application
• Latency – depends on latency of L1B products, is there really a need for low-latency products?
• Gaps – procedures to deal with gaps still have to be developed. Altimetry community has experience with „reconstruction“ of fields. Can other data sources (superconducting gravimeters, SLR, GPS inversion) help?
• Dealiasing procedure and products (next slides)
GRACE Standard Products & How to use them
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Generation of GRACE Standard L2 Products (Flechtner 9/11)
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Generation of GRACE Standard AODB Products (Flechtner 9/11)
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Generation of GRACE Standard AODB Products (Flechtner 9/11)
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Monthly sets of spherical harmonics – AOD products
GRACE Standard Products & How to use them
Recommended use of GRACE Standard AODB Products (Flechtner 9/11)
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Monthly sets of spherical harmonics – AOD products
GRACE Standard Products & How to use them
Recommended use of GRACE Standard AODB Products (Flechtner 9/11)
For hydrology applications:
• No need to restore AOD product
• WARNING: AOD is not consistent with IB correction in altimetry, this has to be considered when combining GRACE and lake/coastal altimetry
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Degree-1 (C10.C11,S11): addfrom other data sources
GRACE Standard Products & How to use them
Geocenter motion (Rietbroek et al. 2011)
EWH corresponding to degree 1(Swenson & Wahr 2007)
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Degree-1 and C20 (Flechtner, 9/11)
GRACE Standard Products & How to use them
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Enhanced temporal resolution• Daily GRACE solutions• Weekly GRACE solutions• Monthly GRACE solutions
Enhanced spatio-temporal resolution• Masscon solutions• RBF solutions
Multisensor combination products• GRACE/GPS/OBP
Post-processed products• Decorrelated solutions• Maps of rates, accelerations and annual components• Mode decompositions
GRACE Non-Standard Products & Procedures
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From L1 data to L2/“L3“ data
GRACE Non-Standard Products & Procedures
L1 data (KBR, GPS, ACC, ATT)
Geophysical model(loading)
Intermediate functional (LOS acc., potential
difference, …)
Gravity potentialparameterization
EWHparameterization
Modified from Panet et al (2009)
Geophysical background models
Satellite altitude Earth‘s surface
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Daily GRACE SH solutions (Bonn University, Kurtenbach et al, 2009)
• Low spatial resolution but high temporal resolution• Not a combination, uses only stochastic constraints• Used as well in de-aliasing of ITG2010 monthly solutions
GRACE Non-Standard Products & Procedures
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1-day predictionGRACE daily NEQs
Daily GRACE SH solutions (Bonn University)
• Low spatial resolution but high temporal resolution• Not a combination, uses only stochastic constraints• Used as well in de-aliasing of ITG2010 monthly solutions
GRACE Non-Standard Products & Procedures
Weighted combination(Kalman-Filter/RTS-Smoother)
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Monthly GRACE SH solutions (Bonn University)• Using daily solutions for dealiasing (instead of AOD product)
GRACE Non-Standard Products & Procedures
equiv
ale
nt
wate
r heig
ht
[cm
]
without
with
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Monthly GRACE SH solutions (Bonn University) – West Africa
GRACE Non-Standard Products & Procedures
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Enhanced spatio-temporal resolution („regional“ approaches“, using regional constraints)
• RBF solutions (Eicker, Holschneider,…)– Compute a harmonic gravity model (L2) with less base functions,
avoiding SH expansion, L3 EWH using Love numbers• Masscon solutions (Rowlands, Ramillien, …)
– Direct modelization of EWH (L3) or use of SH expansion• Basin-shaped „masscons“ (Wouters, Sandberg-Sørensen…)
– Derived from gridded L2 products at altitude
GRACE Non-Standard Products & Procedures
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RBF solutions (Eicker et al, Uni Bonn) • Compute a harmonic gravity model (L2) with less base
functions, avoiding SH expansion, L3 EWH using Love numbers
GRACE Non-Standard Products & Procedures
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Masscon solutions (standard 4ox4o, isotropic constraints)
Krogh et al (2011), 10d x 1.5o/1.25o x 1o, regional constraints (RC)
GRACE Non-Standard Products & Procedures
GLDAS GRGS-504o mascon
1.5o mascon mascon RC mascon RC-50
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Fundamental difference: Implementation of constraints in the masscon approach (Rowlands et al 2010, Sabaka et al 2010)
GRACE Non-Standard Products & Procedures
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Fundamental difference: Implementation of constraints in theRBF/Kalman filter approach (Eicker 2008, Kurtenbach 2011)
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Post-processing of SH products• Gauss-filtering• Decorrelated/destriped solutions: Swenson and Wahr 2006,
Kusche 2007• Mode decompositions (EOF, ICA)
GRACE Non-Standard Products & Procedures
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GRACE SHC
Treatment degree 1 & 2, temporal anomalies wrt epoch t, restore AOD
OR Filtering (in space domain)
Mapping to space domain or basin averaging
Filtering (in spectral domain)
SHA geophysical model SHC
Temporal alignement, possibly remove deg. 1 consistent to GRACE
OR Filtering (in space domain)
Mapping to space domain or basin averaging
Filtering (in spectral domain)
Multiplication in spectral domain
Convolution on the sphere
Globally defined?
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GRACE SHC
Treatment degree 1 & 2, temporal anomalies wrt epoch t, restore AOD
Mapping to space domain or basin averaging
Filtering (in spectral domain)
Geophysical model
Temporal alignement, possibly remove deg. 1 consistent to GRACE
Filtering (in space domain)
Mapping to space domain or basin averaging
Filtering (in spectral domain)
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Destriping filters
Swenson & Wahr 2006
GRACE Non-Standard Products & Procedures
Gridded destriped fields: GRACE Tellus site
http://grace.jpl.nasa.gov/
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Destriping filters
Kusche 2007 („DDK filters“)
Destriped models and grids: GFZ ICGEM site
http://icgem.gfz-potsdam.de/ICGEM/
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Destriping filters and WRMS reduction
GRACE TWS WRMS [cm], 3 filters
stronger lessfiltering
GRACE Non-Standard Products & Procedures
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Post-processed products• Mode decompositions
GRACE Non-Standard Products & Procedures
1. Decompose the hydrological model into statistically independent regimes– begin with PCA – sacrify spatial orthogonality and employ higher-order statistics HOS
ICA2. Bin the GRACE TWS solutions into these statistically independent
regimes
Forootan & Kusche (accepted for J Geodesy)
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Decomposition into statistically independent regimes (1. begin with PCA 2. sacrify spatial orthogonality and employ higher-order statistics HOS)
E. Forootan
Post-processed products• Mode decompositions
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GRACE-FO
– NASA-DLR partnership (as with GRACE)– anticipated launch 15 November 2016– Nominal lifetime 5 y, anticipated 7 y– Will carry
• K-band ranging instrument (as with GRACE)• Laser ranging instrument as add-on
Beyond GRACE-FO– e.motion proposal (ESA EE-8 call, not selected)– ESA NG2 studies
• Multiple pairs of satellites (e.g. Bender configuration)?• Quality of background models?
Beyond GRACE
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GRACE-FO– Will carry
• K-band ranging instrument (as with GRACE)• Laser ranging instrument as add-on
Beyond GRACE
v v
AEI, Hannover
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Science Requirements (from e.motion proposal)
Signal amplitudes of mass variations in EWH as a function of spatial resolution, together with present-day and e.motion performance and resolution. Solid Earth mass variations are converted to EWH. Contributions from seasonal to interannual variations (left panel), and contributions from long-term trends (right panel).
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Gain from the next generation of gravity missions for hydrology and water management (from NG2 study): more & smaller basins
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• GRACE has provided a unique opportunity for geodesy and hydrology
• With GRACE-FO in reach, and developments starting for missions beyond, we‘re hopefully heading towards an operational chain of gravity/mass missions (as in altimetry)
• Future missions will likely push the spatial resolution of GRACE down to 150-200km
• Through a series of reprocessings and through development of non-standard products, GRACE product quality has strongly increased
Thank you for your attention.
Take-home Message
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