New global and regional Mean Dynamic Topographies from the combination of GRACE data, altimetry and in-situ measurements. (Invited)
Abstract
Accurate knowledge of the ocean Mean Dynamic Topography at all spatial scales is mandatory for the full exploitation of altimetric data including their assimilation into operational ocean forecasting systems. In preparation for future GOCE data, whose resolution will allow to estimate the ocean MDT with centimetric accuray at 100km scales, a new global 0.25° resolution MDT has been computed as well as a higher resolution (1/10°) solution around the European coasts (30°W 3°E; 30°N 50°N). The new global Mean Dynamic Topography has been computed, with improved data and methodology compared to the previous RIO05 MDT field: First, a large scale Mean Dynamic Topography was obtained from the CLS01 altimetric Mean Sea Surface and the latest geoid model computed at GRGS from 5 years of GRACE data. Then, altimetric sea level anomalies and in-situ measurements have been combined to compute synthetic estimates of the MDT and the corresponding mean currents. While the RIO05 MDT was based on 9 years of in-situ data (dynamic heights and drifting buoy velocities), the new field benefits from an enlarged dataset of in-situ measurements covering 15 years from 1993 to 2008 and including the latest ARGO reanalysis from the Coriolis center. Moreover the processing of the in-situ data has been improved: A new Ekman model was computed to extract the geostrophic velocity component from the drifting buoy measurements. The handling of hydrologic measurements has also been improved so as to allow for the inclusion of T, S profiles referenced to different pressure levels in the computation of the synthetic heights, resulting in a better sampling of the ocean, mainly in coastal areas. At more regional scales, where the resolution of future GOCE data will be too coarse, higher resolution gravity information is needed. High resolution (5’) estimates of both the Mean Sea Surface and the geoid model have been computed for the European coasts (30°W 3°E; 30°N 50°N) which were then used, in combination with oceanographic and altimetric data, to compute a high resolution MDT over the area (1/10°). These New global and regional MDTs will be very helpful to validate future GOCE data for oceanographic applications.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.G53D0701R
- Keywords:
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- 1222 GEODESY AND GRAVITY / Ocean monitoring with geodetic techniques;
- 4223 OCEANOGRAPHY: GENERAL / Descriptive and regional oceanography;
- 4532 OCEANOGRAPHY: PHYSICAL / General circulation