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Generation of Climate Data Records from Ocean Radar Altimetry

Brian Beckley(1) , Richard Ray(2) , David Rowlands(2) , Frank Lemoine(2) , Nikita Zelensky(3) , Douglas Vandemark(4) , and Scott Luthcke(2)

(1) Raytheon, NASA/GSFC Code 614.2, Greenbelt 20771, United States
(2) NASA, NASA/GSFC Code 697, Greenbelt 20771, United States
(3) SGT Inc., 7701 Greenbelt Road Suite 400, Greenbelt 20770, United States
(4) University of New Hampshire, Ocean Process Analysis Laboratory 39 College Rd., Durham 03824, United States


Satellite radar altimetry mapping of the ocean surface has achieved remarkable success in recent years, yet is one of the most complex forms of remote sensing. These systems produce measures of the sea surface height within a dynamically evolving reference frame, along with a measure of the sea state. A consistent geodetic reference system and set of correction algorithms for all altimetric missions are essential so that a time change in a series built from two or more altimetric missions can be interpreted as a change in sea level, and not in the measuring system. However, in concert with this challenge for consistency is the realization that state of the art entails a constant state of change, including data coming from new missions which must be brought into a common frame with existing data, improved estimates of instrument drift, and a continuous upgrade of algorithms as a result of access to better data (e.g. GRACE) over time. Thusly, value can continuously be added to existing data holdings and these holdings significantly expand over time. With a goal of using these data to measure unambiguously sub-mm changes in global sea level and producing a valuable Climate Data Record database, altimeter science retains an evolutionary character despite its current “operational” status and perception. Here we present the impact of recent improvements to both the current level of TOPEX/Poseidon (T/P) orbit accuracy (from the current 2-cm level to better than 1.5-cm) through reduced dynamic methods based on the latest GRACE derived gravity field within a consistent well defined terrestrial reference frame, as well as improved GPS based orbits for Jason-1. The anticipated success of this effort will provide a seamless transfer from T/P to Jason-1, directly improve correction algorithms empirically derived from sea surface height measurements (i.e. revised GOT ocean tide model, sea state bias, and ionosphere corrections) thus improving the ability to isolate subtle yet highly significant long period signals, and provide an improved coincident reference frame for ENVISAT and GFO.



                 Last modified: 07.10.03