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The DNSC08MDT Mean Dynamic Topography

The DNSC08MDT Mean Dynamic Topography. Ole B. Andersen and P. Knudsen (DTU-SPACE). The DNSC08MDT. The DNSC08 Mean Dynamic Topography. The DNSC08 is developed from the DNSC08 Mean Sea surface and the EGM2008 Geoid model using the geometrical difference:. MDT = MSS – Geoid .

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The DNSC08MDT Mean Dynamic Topography

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  1. The DNSC08MDT Mean Dynamic Topography Ole B. Andersen and P. Knudsen (DTU-SPACE)

  2. The DNSC08MDT EGU meeting, Vienna, Austria | April 2008 | OA | page 2

  3. The DNSC08 Mean Dynamic Topography • The DNSC08 is developed from the DNSC08 Mean Sea surface and the EGM2008 Geoid model using the geometrical difference: MDT = MSS – Geoid  EGU meeting, Vienna, Austria | April 2008 | OA | page 3

  4. Difference with RIO05 MDT (meters). There is a global un-defined mean offset EGU meeting, Vienna, Austria | April 2008 | OA | page 4

  5. The DNSC08 Mean Dynamic Topography • The DNSC08 is developed from the geometrical difference between the DNSC08 Mean Sea surface and the EGM2008 Geoid model using the difference: • Subsequently the Difference have been smoothed using a gaussian smoother with a halfwidth of 75km. • Notice: The mean sea surface and the Geoid will consequently coincide for shorter spatial wavelength as the altimetric gravity anomalies are introduced in the derivation of the global geoid. • Consequently shorter wavelength in the MDT might not be accurately mapped in the DNSC08 MDT • DNSC08MSS Min and max values are -1.86 m and +1.35 meters. The average is 0.23 meters MDT = MSS – Geoid  EGU meeting, Vienna, Austria | April 2008 | OA | page 5

  6. The DNSC08 Mean Dynamic Topography • The global mean of the difference between EGM2008 and DNSC08MSS is 23 cm integrated over all oceans of the world (but not spatially weighted). • This difference have not been accounted for in DNSC08MDT which will have a mean of 23 cm. The average of OCCAM 1993-2001 is 18 cm. • The mean and the MDT is representable for the period 1993-2004. EGU meeting, Vienna, Austria | April 2008 | OA | page 6

  7. Inter-Annual variation relative to global trend Annual mean offsets relative to mean and sea level trend over the 1993-2004 period 1993 1994 1995 1996 1999 2001 EGU meeting, Vienna, Austria | April 2008 | OA | page 7

  8. Consistent Inter-annual Sea Level variation Assuming the geoid is stationary Geoid = MSS – MDT, G (period1) = G (period2) The MDTs / MSS’s adjusted for the inter-annual sea level variations is MDT(period1) = MDT(period2) + ΔMSS(period1) - ΔMSS(period2) EXAMPLE: The MDT model represent the period 1993-2001 will then be MDT(93-01) = MDT(04-93) - ΔMSS(93-01) (as ΔMSS(93-04) = 0) DNSC08MSS/MDT is provided with a program to perform this correction EGU meeting, Vienna, Austria | April 2008 | OA | page 8

  9. DNSC08-OCCAM Synhtetic Geoid Model DNSC08 MSS The OCCAM 93-95 MDT The 93-95 -> 93-01 Interannual Sea Level Anomaly Correction. DNSC08 MSS - OCCAM MDT synthetic geoid. Consistent inter-annual SLA modelling EGU meeting, Vienna, Austria | April 2008 | OA | page 9

  10. Summary • DNSC08 Suite of Global Fields • Resolution: 1 minute by 1 minute (2 km by 2 km) • True global fields (90°S to 90°N) • DNSC08: ftp.spacecenter.dk/pub/MDT • DNSC08 All files: ftp.spacecenter.dk/pub/DNSC08 (all files) • DVD: Contact oa@space.dtu.dk • Consistent Products available: • Altimetric (geometrical) MSS DNSC08-MSS • Altimetric derived Bathymetry DNSC08-BAT • Altimetryc derived MDT DNSC08-MDT • Altimetric Marine Gravity field DNSC08-GRA • Products also available in Google Earth EGU meeting, Vienna, Austria | April 2008 | OA | page 10

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