GRACE Products for Oceanography Don Chambers Center for Space Research The University of Texas at Austin Victor Zlotnicki Jet Propulsion laboratory California Institute of Technology OST Science Team Meeting St. Petersburg, FL November 4-6 2004
Dynamic Ocean Topography (DOT) = Mean Sea Surface (MSS) - geoid • MSS is MSS used for Jason GDRs (GSFCMSS00) • Geoid is based on new average from GRACE SDS at CSR, GGMO2C • 363-days of satellite information combined with surface gravity • Complete to degree/order 200 • Can be extended to degree/order 360 with EGM96 with no obvious discontinuity
Slide 1 DOT 0 Dynamic Ocean Topography (DOT) = GSFCMSS00 - GGM02C geoid; GGM02C extended to degree 360 with EGM96
Slide 2 DOT 1 Map DOT to 0.5° grid using a Gaussian spatial smoother; filter suppresses signals with wavelengths < 888 km.
Slide 3 DOT 0 - DOT 1 Residual signal in full resolution DOT (DOT 0) unresolved by smoothing (DOT 1); evident features related to circulation (e.g., arrows), but also signals related to geoid (e.g., vertical stripes, seamounts, trenches).
Slide 4 Smooth residual signal (DOT 0 - DOT 1) to keep features related to circulation, but not geoid; because of vertical striping, use spherical harmonic (SH) expansion to degree 360 and weighted coefficients with a function in SH space equivalent to a spatial Gaussian with a half-width of 222 km [Wahr et al., JGR, 1998].
Slide 5 DOT 2 Add smoothed residual signal to DOT 1.
Slide 6 DOT 0 - DOT 2 Still some residual signal which appears to be related to ocean circulation, but not as much as before.
Slide 7 Smooth residual signal (DOT 0 - DOT 2) as before but with a SH-equivalent half-width of 200 km. We find that at any smaller radius, the vertical stripes begin to appear.
Slide 8 Final DOT Add smoothed residual signal to DOT 2.
Slide 9 Zonal geostrophic currents implied by Final DOT. Eastward is positive.
Slide 10 Meridional geostrophic currents implied by Final DOT. Northward is positive.
DOT and circulation grids (at 0.5° resolution) will soon be available from PODAAC • Other items to follow • Along-track DOT from Jason-1 SLA products • Monthly climatology DOT • Sub-surface circulation maps from combination with World Ocean Atlas 2001 • Funding for project from NASA • Earth Science Research, Education and Applications Solutions Network (Earth Science REASoN ).