100 likes | 183 Views
INVERSION OF GRACE GEOIDS FOR LAND HYDROLOGY C. Reigber, R. Schmidt (GFZ, Potsdam) G. Ramillien, A. Cazenave (LEGOS, Toulouse). Seasonal signal in land water storage. Global Models : Atmosphere : ECMWF(79-93), NCEP(79-96) Oceans : POCM(79-97),ORCA(92-99),
E N D
INVERSION OF GRACE GEOIDS FOR LAND HYDROLOGY C. Reigber, R. Schmidt (GFZ, Potsdam) G. Ramillien, A. Cazenave (LEGOS, Toulouse) Seasonal signal in land water storage
Global Models : Atmosphere : ECMWF(79-93), NCEP(79-96) Oceans : POCM(79-97),ORCA(92-99), MIT(85-96), ECCO assimilation (1993 -…) Soil moisture & Snow cover : LaD(81-98),GSWP(87-88),Huang(79-98) Observed monthly mean variations of the geoid A priori uncertainties of Models and GRACE obs. Inversion for « De-correlation » (Generalized least-squares matrix solving) STEP 1 Maps of geoid anomaly for each hydrological contribution Atmosphere Oceans Soil moisture Snow cover Predictive filtering of the spherical coefficients + compensation (elastic Earth’s response to surface loads) STEP 2 Distribution of surface water masses
: solution vector formed by the list of all spherical harmonic coefficients to be solved • : vector formed with GRACE-derived geoid coefficients • : vector formed by the list of all spherical harmonic coefficients of the ‘first guess’ • : matrix composed of 4 diagonal blocks for separating the 4 reservoirs contributions • : covariance matrices of the ‘a priori’ GRACE errors and a priori model uncertainties • : covariance matrix which describes the statistical properties of the water mass variations in the ‘k-th’ reservoir The solution is computed by solving the linear equation:
GRACE geoids (GFZ) April 2002 May 2002 November 2002
May 2002-Nov.2002 (seasonal cycle) Total land water (soil water + snow) Lad(1rst guess) GSWP (1rst guess)
May02-Nov02 (seasonal cycle) GRACE geoids from CSR Total land water (soil water + snow)
May-Nov. (seasonal cycle); Models Total land water (soil water + snow) LaD GSWP
Residuals : GRACE(GFZ) minus solution; seasonal cycle LaD as 1rst guess GSWP as 1rst guess
Seasonal cycle of total land waters (April+May) 2002 minus November 2002 GFZ geoids Same solution whatever the first guess