Modeling Marine Gravity Potential with Satellite Altimetry Data
Dettmering, Denise; Schmidt, Michael; Bosch, Wolfgang; Lieb, Verena
Deutsches Geodätisches Forschungsinstitut (DGFI), GERMANY

Sea Surface Height (SSH) measurements from radar altimetry missions are the primary source of information for marine gravity field modeling. In contrast to other satellite based gravity measurements the data are directly related to the ground and no downward continuation from orbit height is necessary. Consequently, much higher spatial resolution can be reached compared to dedicated gravity missions (GRACE, GOCE). Particularly, the geodetic mission phases of GEOSAT, ERS-1, and Jason-1 as well as the long repeat-cycle mission Cryosat-2 can provide valuable information for high resolution marine gravity field modeling.

In the present paper we do not follow the traditional Stokes or Vening Meinesz approach. Instead we use absolute SSH profiles of different altimeter missions to compute high resolution regional gravity field models over the ocean. In combination with sea surface topography information, the SSH is used as input data for the estimation of the unknown coefficients of our model, which is set up as a series expansion in spherical base functions, i.e. spherical scaling functions, in order to estimate corrections to a given background model (e.g. GOCO03S). The consistency of the different altimeter missions is reached by a pre-processing crossover analysis which also ensures that long-wavelength errors such as orbit errors are eliminated beforehand. The approach has several advantages over the inversion of Stokes or Vening Meinesz integrals: A combination with other input data types such as GOCE gravity gradients is possible in order to stabilize the results in lower frequency bands. Moreover the estimation of the gravity potential allows deriving not only geoid undulations but any functional of interest, e.g. gravity anomalies or gravity gradients.

The presentation will be separated in three parts: After an introduction of the modeling approach, results of regional marine gravity modeling will be presented based on observations from ERS-1, Cryosat-2, and Jason-1. In the last part, global models as well as ship-borne measurements will be used to validate the regional models.