recent applications of grace gravity data for continental hydrology andreas güntner helmholtz...
TRANSCRIPT
Recent applications of GRACE gravity data for continental hydrology
Andreas Güntner
Helmholtz Centre PotsdamGFZ German Research Centre for Geosciences
Andreas Güntner | GRACE for continental hydrology 2
Water storage variations from time-variable gravity data
Temporal variations of the gravity field of the Earth
Water mass variations on the continents after removal of other mass components S: Water storage change
P: PrecipitationE: EvaporationQ: Runoff
ΔS = P - Q - E
Only integrative and large-scale measurement of ΔS for hydrology
Andreas Güntner | GRACE for continental hydrology 3
11/2011: About 200 ISI paper on GRACE and continental hydrology
Water storage variations 169
- Total water storage 104
- Groundwater 25
- Inland glaciers 13
- Surface water storage 19
- Snow 6
Water balance, other variables 33
Evaluation of hydrological models 31
- Model calibration / data assimilation 7
GRACE processing, filtering 54
Main focus of GRACE hydrology papers
Andreas Güntner | GRACE for continental hydrology 4
11/2011: About 200 ISI paper on GRACE and continental hydrology
Studies on water storage variations for particular river basins
Andreas Güntner | GRACE for continental hydrology 5
ET = P - Q - ΔS
Water cycle components from GRACE data - Resolving for evapotranspiration
Ground and/or satellite-based data GRACE
Andreas Güntner | GRACE for continental hydrology 6
ET = P - Q - ΔSWater cycle components from GRACE data - Resolving for evapotranspiration
Moiwo et al. (2011), Hydr.Sci.J.
Hai River Basin, North China (320 000 km²)
ETWH: Model-based ET using remote sensing data
ETGP: GRACE-based ET
Andreas Güntner | GRACE for continental hydrology 7
Water cycle components from GRACE data - Resolving for continental runoff
ΔS = P – Q - ET
Atmospheric water balance
ΔW = C + ET - P
Terrestrial water balance
S Land water storage changeP PrecipitationET EvaporationQ RunoffW Atmospheric water storage changeC Water vapour convergence
Q = -ΔW + C - ΔS
Combined atmospheric-terrestrial water balance
Andreas Güntner | GRACE for continental hydrology 8
Water cycle components from GRACE data - Resolving for continental runoff
Syed et al. (2007), GRL
+ includes ungauged river basins
+ includes groundwater discharge into oceans
Total continental discharge of the Pan-Arctic drainage area
Andreas Güntner | GRACE for continental hydrology 9
Water storage variations from time-variable gravity data
ΔTWSGRACE = ΔSgroundwater + ΔScanopy + ΔSsnow + ΔSsoil + ΔSlakes + ΔSwetlands + ΔSriver
GRACE-based total water
storage variations ΔTWSGRACE
are a composite of various
continental water storage
compartments
Andreas Güntner | GRACE for continental hydrology 10
GRACE hydrology studies with focus on lake water balances
9 studies among 200 ISI papers on GRACE and continental hydrology (11/2011)
Andreas Güntner | GRACE for continental hydrology 11
GRACE hydrology studies with focus on surface water dynamics(river flow, floodplains, inundation areas)
15 studies among 200 ISI papers on GRACE and continental hydrology (11/2011)
Andreas Güntner | GRACE for continental hydrology 12
GRACE hydrology studies with focus on inland glaciers
13 studies among 200 ISI papers on GRACE and continental hydrology (11/2011)
Andreas Güntner | GRACE for continental hydrology 13
GRACE hydrology studies with focus on groundwater storage variations
25 studies among 200 ISI papers on GRACE and continental hydrology (11/2011)
Andreas Güntner | GRACE for continental hydrology 14
Water storage variations from time-variable gravity data
ΔSgroundwater = ΔTWSGRACE + ΔScanopy + ΔSsnow + ΔSsoil + ΔSlakes + ΔSwetlands + ΔSriver
Resolving GRACE-based total
water storage variations
ΔTWSGRACE for single storage
compartments
• Other compartments can usually be estimated based on hydrological / land surface model data only
• Other compartments may not be fully accounted for in models
• Uncertainties / errors accumulate in the variable of interest
Andreas Güntner | GRACE for continental hydrology 15
WaterGAP Global Hydrology model (WGHM)
ISBA-TRIP
Global Land Data Assimilation System (GLDAS)
ΔTWS = ΔScanopy + ΔSsnow + ΔSsoil + ΔSgroundwater + ΔSrivers + ΔSlakes/reservoirs + ΔSwetlands
ΔTWS = Δ Scanopy +ΔSsnow + ΔSsoil + ΔSgroundwater + ΔSrivers
ΔTWS = ΔScanopy + ΔSsnow + ΔSsoil
Soil depth = root zone
Soil depth = root zone + deep soil layer
Soil depth GLDAS-CLM = 3.43 mGLDAS-MOSAIC = 3.50 mGLDAS-NOAH = 2.00 mGLDAS-VIC = 1.90 m
Water storage compartments from hydrological modelsfor GRACE TWS signal separation
Andreas Güntner | GRACE for continental hydrology 16
Relevance of deep unsaturated zone water storage for GRACE TWS signal separation
Snow
Soil 0-30cm
Soil 30-150cm
Saprolith 1.5 – 11m
Groundwater > 11m
Creutzfeldt et al., 2010, WRR; Creutzfeldt et al., GJI, 2010
Hydrological gravity effect
Superconducting gravimeter residuals
Local gravity effect of water storage compartments
Station Wettzell / Germany
Un
satu
rate
d zo
ne
Andreas Güntner | GRACE for continental hydrology 17
Example: Water storage variations in Central Asian Mountains
Total study area:500 000 km²
Andreas Güntner | GRACE for continental hydrology 18
Example: Water storage variations in Central Asian Mountains
Source: GGHYDRO (Cogley, 2003)
Total study area:500 000 km²
Can we estimate glacier mass changes from GRACE?
Andreas Güntner | GRACE for continental hydrology 19
1) Selection of GRACE product (processing type and centre, filtering)
2) Compensation for filter effects (smoothing, leakage)
Estimating correction function (e.g. rescaling factor)
Hydrological models
3) Reduction of unwanted hydrological signal components
4) Analysis of residuals
Isolation of single water storage compartmentsfrom GRACE TWS data
Andreas Güntner | GRACE for continental hydrology 20
Water storage variations in Central Asian Mountains
Andreas Güntner | GRACE for continental hydrology 21
1) Selection of GRACE product (processing type and centre, filtering)
2) Compensation for filter effects (smoothing, leakage)
Estimating correction function (e.g. rescaling factor)
Hydrological models
3) Reduction of unwanted hydrological signal components
4) Analysis of residuals and error assessment
Isolation of single water storage compartmentsfrom GRACE TWS data
Ensemble of GRACE products
Andreas Güntner | GRACE for continental hydrology 22
Water storage variations in Central Asian Mountains
Andreas Güntner | GRACE for continental hydrology 23
Water storage variations in Central Asian Mountains
Andreas Güntner | GRACE for continental hydrology 24
Compensation for filter effects
Multiplicative scaling factor derived from least-square adjustment
• Mainly sensitive to seasonal dynamics
• Leakage effects (e.g. phase shifts) are not compensated
• Rescaling functions depend on the hydrological model used
• Rescaling functions may not apply for the variable of interest
Andreas Güntner | GRACE for continental hydrology 25
Compensation for filter effects: example Central Asia
Multiplicative scaling factor derived from least-square adjustment
CLM MOSAIC NOAH VIC ISBA-TRIP WGHM
G300 1.47 1.32 1.18 1.29 0.99 0.98
G500 1.70 1.51 1.20 1.65 0.95 1.08
DDK1 1.63 1.54 1.23 1.68 1.02 1.17
DDK2 1.55 1.48 1.20 1.75 0.91 1.06
DDK3 1.83 1.63 1.21 1.84 0.85 1.06
G300/G500: Gauss filter 300/500 km. DDK: Decorrelation filter by Kusche (2007)
Andreas Güntner | GRACE for continental hydrology 26
Compensation for filter effects: example Central Asia
Multiplicative scaling factor derived from least-square adjustment
CLM MOSAIC NOAH VIC ISBA-TRIP WGHMWGHM
No surface storage
G300 1.47 1.32 1.18 1.29 0.99 0.98 1.11
G500 1.70 1.51 1.20 1.65 0.95 1.08 1.45
DDK1 1.63 1.54 1.23 1.68 1.02 1.17 1.58
DDK2 1.55 1.48 1.20 1.75 0.91 1.06 1.23
DDK3 1.83 1.63 1.21 1.84 0.85 1.06 1.45
G300/G500: Gauss filter 300/500 km. DDK: Decorrelation filter by Kusche (2007)
Andreas Güntner | GRACE for continental hydrology 27
1) Selection of GRACE product (processing type and centre, filtering)
2) Compensation for filter effects (smoothing, leakage)
Estimating correction function (e.g. rescaling factor)
Hydrological models
3) Reduction of unwanted hydrological signal components
4) Analysis of residuals and error assessment
Isolation of single water storage compartmentsfrom GRACE TWS data
Ensemble of GRACE products
Carefully consider particular region and model differences
´ (e.g., Werth et al. 2009,Longuevergne et al. 2010)
Andreas Güntner | GRACE for continental hydrology 28
Reducing GRACE mass variations in Central Asian Mountainsby water storage from hydrological models
- 7 GRACE products
- 5 different filters
- 6 different rescaling values for each filter
- 6 different LSMs / hydrological models for signal separation
→ bootstrapping approach
Andreas Güntner | GRACE for continental hydrology 29
GRACE mass variations in Central Asian Mountains after reducing for model-based TWS
792 realisation of different plausible GRACE products, rescaling factors and hydrological reduction models
Trend-0.2 ± 5.7 mm/a
Andreas Güntner | GRACE for continental hydrology 30
GRACE mass variations in Central Asian Mountains after reducing for model-based TWS
792 realisation of different plausible GRACE products, rescaling factors and hydrological reduction models
Trend+13.9 mm/a
Trend-12.8 mm/a
Andreas Güntner | GRACE for continental hydrology 31
Conclusions and perspectives
• Caveats in using single GRACE products, filter and correction methods or hydrological model data sets→ use ensemble approach
• Multi-sensor applications of GRACE (in conjunction with, e.g., altimetry, satellite-based snow, soil moisture and ET products) for assessing dynamics of continental hydrology and signal decomposition
• Extended use of GRACE to inform structure and parameterization of land surface / hydrological models