CoAuthors

Victor Zlotnicki (Jet Propulsion Lab, Pasadena, CA, USA); Zheng Qu (Raytheon, Co, Pasadena, CA, USA)

A NASA "Making Earth System Data Records for Use in Research Environments" (MEaSUREs) program activity is partially funding several improvements to altimetry data, such as orbits, sea state bias, etc, in a collaboration between the Jet Propulsion Laboratory, Goddard Space Flight Center, U. South Florida, U. Colorado and U. New Hampshire. As part of this activity, we are generating a new set of altimetric grids, which will eventually be produced and distributed as a new, value added altimetry product. At this stage, we are testing gridding algorithms using just two satellites at any one time. The underlying data for the T/P, J1, J2 series use the GSFC std1204 orbits computed at the Goddard Space Flight Center (using time-variable gravity), GOT4.8 (GSFC Ocean+load) tide model, cross-track gradient correction based on slopes from DTU10 MSS, as well as GDR-D versions of the remaining corrections. For the 'other' satellite (ERS-1,2, Envisat, SARAL/AltiKa) we use R. Scharroo's RADS products, allowing for long wavelength errors and increased noise level in the gridding routine; for near-real time AltiKa we use S. Desai et al. data product, crossover-adjusted to Jason-2. We are currently using the same covariance functional form used in the Dibarboure/LeTraon series of papers and currently used by CLS/CNES, but with a newly-derived map of spatial zero-crossings of the covariance function (and its RMS). The maps are on a 1/6 degree grid. We evaluate the maps by withholding data every so often and comparing the interpolated results with the withheld altimetric data; the final maps include all the data. We present results in terms of spectral content, RMS discrepancy and other quality measures. We discuss expected future developments. Contact: victor.zlotnicki[at]jpl.nasa.gov