Simulation Results from Combination of GOCE Gridded SST and SGG Data
Abstract
EGM96 spherical harmonic coefficients from degree 25 to 60 have been used to produce grids of values of the anomalous potential,. T, the first order derivatives, Tr, Tn, and various second orderderivatives in an East, North, radial frame, (Trr ,Tre ,Tee, Tnn )Various combinations of the data has been used to recover the potential coefficients using the method of Fast Spherical Collocation (FSC). A covariance function with the terms up to degree 25 equal to the EGM96 error degree-variances was used. Terms from degree 25 to infinity were chosen so that the covariance function could be evaluated using a closed expression.The simulation shows that using Tre ,Tee, Tnn, Trr , and combining Tre ,Tr, Tn nearly give the same result. That Tnn ,Tee , gives the same results, but combining Tee with Tnn improves the results. Tr ,Trr ,and a joint use of Trr, Tr also gives nearly the same results, while the results using the "horizontal" derivatives are up to a factor 2 worse per degree.Since the covariance function contain terms from degree 2 to infinity, spherical harmonic coefficients in the range 2 - 24 will be predicted with results which are non-zero, despite the input data do not contain corresponding harmonic coefficients different from zero. Consequently the predicted values show the effect of how the different data types "aliases" back into degrees 2 - 24. Here T and Tr give the smallest aliasing.
- Publication:
-
GOCE, The Geoid and Oceanography
- Pub Date:
- June 2004
- Bibcode:
- 2004ESASP.569E..30T