igcp565 and africaarray workshop standard and non-standard grace products for hydrology jürgen...

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


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


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


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

LSM

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Hydrology – Henry et al. (2011):GRACE TWS – GLDAS Soil moisure = Groundwater variation


Avg. GW

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Hydrology – Becker et al. (2010,C.R. Geoscience)


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GRACE standard products• L2 level: Monthly spherical harmonic expansions of gravity potential

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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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iggGRACE Standard Products & How to use them

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


Recommended use of GRACE Standard AODB Products (Flechtner 9/11)

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Monthly sets of spherical harmonics – AOD products


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


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)


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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


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


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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


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)


equiv

ale

nt

wate

r heig

ht

[cm

]

without

with

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Monthly GRACE SH solutions (Bonn University) – West Africa


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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


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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


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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)


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)


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iggGRACE Non-Standard Products & Procedures

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)


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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)



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



Geophysical model

Temporal alignement, possibly remove deg. 1 consistent to GRACE

Filtering (in space domain)



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Destriping filters

Swenson & Wahr 2006


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


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Post-processed products• Mode decompositions


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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iggBeyond GRACE

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

igcp565 and africaarray workshop standard and non-standard grace products for hydrology jürgen...

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