Using Satellite Gravimetry for Validating the Water Cycle in Global and Regional Atmospheric Reanalyses 1 Anne Springer, Jürgen Kusche, Annette Eicker Institute of Geodesy and Geoinformation, Bonn University, Germany Christian Ohlwein, Christoph Bollmeyer, Jan Keller Meteorological Institute, Bonn University, Germany Laurent Longuevergne CNRS – Géosciences Rennes, France Susanne Crewell Institute for Geophysics and Meteorology, Cologne University, Cologne, Germany Anne Springer Earth Observation for Water Cycle Science 21/10/2015 The water budget equation ΔS=P-E-R Precipitation P 2 Evapotranspiration E Storage S Discharge R Anne Springer Earth Observation for Water Cycle Science 21/10/2015 The water budget equation ΔS+R=P-E 3 P - E represents: • an important boundary condition for hydrological studies and climate modeling. • an indicator for the intensification of the water cycle. • the coupling of the Earth’s water and energy cycles. Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Data sets ΔS+R=P-E GFZ GRACE Release 05a 4 Regional Analysis Regional Reanalysis Global Reanalyses GRDC BfG Observations Anne Springer Earth Observation for Water Cycle Science COSMO-EU COSMO-REA6 ERA-Interim MERRA MERRA-Land MPI (E) GPCC (P) E-OBS (P) 21/10/2015 GRACE & Water budget studies Evapotranspiration, Mississippi Discharge, Global Rodell et al., 2004 Syed et al., 2009 5 P-E, Danube Springer et al., 2014 Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Availability of discharge 2003 - 2012 Availability of monthly discharge data from GRDC and BfG for 2003 -2012. Anne Springer Earth Observation for Water Cycle Science 6 21/10/2015 COSMO-REA6: a regional reanalysis Data assimilation: Continuous nudging scheme wind, temperature, humidity, pressure Surface analysis: Snow depth, sea surface temperature, soil moisture 7 Boundary data: ECMWF ERA-Interim Bollmeyer et al. (2015): Towards a high-resolution regional reanalysis for the European CORDEX domain Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Study area 8 SIze [km2] Region Anne Springer Meuse 27 000 Rhine 160 000 187 000 Ems 8 000 Weser 38 000 Elbe 132 000 Oder 110 000 110 000 Danube 807 000 807 000 Earth Observation for Water Cycle Science 178 000 21/10/2015 Processing strategy Aim: consistent time series of ΔS & P-E Careful processing of GRACE data: • Degree 1 coefficients replaced • c20 coefficient replaced • GIA model applied 9 • DDK4 filter • Central differences • Time-variable rescaling factor Springer, et al. (2014) New Estimates of Variations in Water Flux and Storage over Europe Based on Regional (Re)Analyses and Multisensor Observations. Anne Springer Earth Observation for Water Cycle Science 21/10/2015 P-E = ΔS+R 10 Anne Springer Earth Observation for Water Cycle Science 21/10/2015 P-E = ΔS+R: detrended, deseasoned ρ=0.59 …0.64 ρ=0.63 …0.69 11 ρ=0.66 …0.74 Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Consistency: ΔS+R-(P-E)=0 12 Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Power Spectrum Density 13 Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Consistency: ΔS+R-(P-E)=0 14 𝜀 = 𝑎 + 𝑏 sin(2𝜋𝑡) + 𝑐 cos(2𝜋𝑡) + 𝑑 sin(4𝜋𝑡) + 𝑒 cos(4𝜋𝑡) Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Bias COSMO-REA6 COSMO-EU GPCC+MPI 15 ERA-Interim Anne Springer MERRA Earth Observation for Water Cycle Science MERRA-Land 21/10/2015 Total water storage from fluxes: Danube TWSC ΔS = P-E-R 16 TWS Anne Springer S= P−E−R Earth Observation for Water Cycle Science 21/10/2015 Total water storage from fluxes: Danube TWSC ΔS = P-E-R 17 𝜀 = 𝑎 + 𝑏 sin(2𝜋𝑡) + 𝑐 cos(2𝜋𝑡) + 𝑑 sin(4𝜋𝑡) + 𝑒 cos(4𝜋𝑡) TWS Anne Springer S= P−E−R Earth Observation for Water Cycle Science 21/10/2015 Total water storage from fluxes: Danube TWSC ΔS = P-E-R 18 TWS Anne Springer S= P−E−R Earth Observation for Water Cycle Science 21/10/2015 Total water storage from fluxes 19 Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Take Home Messages • Short-term variability: GRACE and models agree notably well even in very small basins. • Constant biases, differences in annual amplitude and phase: regional models perform better than global models. • Reconstructed storage from fluxes: Time-variable biases lead to trends in storage. 20 Further steps: • Extend study to the whole European area • Develop more sophisticated error models • Understand flux-derived storage Anne Springer Earth Observation for Water Cycle Science 21/10/2015 Literatur • Bollmeyer, C., J. D. Keller, C. Ohlwein, S. Wahl, S. Crewell, P. Friederichs, A. Hense, J. Keune, S. Kneifel, I. Pscheidt, S. Redl and S. Steinke (2015) Towards a high-resolution regional reanalysis for the European CORDEX domain. Q. J. R. Meteorol. Soc. 141: 1-15. • Jung, M., M. Reichstein and A. Bondeau (2009) Towards global empirical upscaling of FLUXNET eddy covariance observations: validation of a model tree ensemble approach using a biosphere model. Biogeosciences, 6:2001–2013. • Klees, R., E.A. Zapreeva, H.C. Winsemius and H.H.G. Savenije (2007) The bias in GRACE estimates of continental water storage variations. Hydrol. Earth Syst. Sci., 11:1227–1241. 21 • Kusche, J. (2007) Approximate decorrelation and non-isotropic smoothing of time-variable GRACE-type gravity field models. J. Geodesy, 81:733–749. • Lorenz, C. and H. Kunstmann (2012) The Hydrological Cycle in Three State-of-the-art Reanalyses: Intercomparison and Performance Analysis. J. Hydrometeor., 13:1397–1420. • M. Rodell, J. S. Famiglietti, J. Chen, S. I. Seneviratne, P. Viterbo, S. Holl and C. R. Wilson (2004) Basin scale estimates of evapotranspiration using GRACE and other observations. Geophy. Res. Lett., 31. • T. H. Syed, J. S. Famiglietti (2009) GRACE-Based Estimates of Terrestrial Freshwater Discharge from Basin to Continental Scales. J. Hydrometeor., 10: 22-40. • Springer, Anne, J. Kusche, K. Hartung, C. Ohlwein and L. Longuevergne (2014) New Estimates of Variations in Water Flux and Storage over Europe Based on Regional (Re)Analyses and Multisensor Observations. J. Hydrometeor., 15: 2397-2417. • Wahr, J., M. Molenaar and F. Bryan (1998) Time variability of the Earth’s gravity field: hydrological and oceanic effects and their possible detection using GRACE. J. Geophys. Res.-Solid, 103:30205–30229. Anne Springer Earth Observation for Water Cycle Science 21/10/2015
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