Pointwise comparison of geostrophic currents of altimetry-derived instantaneous Ocean Dynamic Topography with in-situ measurements

Felix Müller (Deutsches Geodätisches Forschungsinstitut der TU München (DGFI-TUM), Germany)


Denise Dettmering (Deutsches Geodätisches Forschungsinstitut der TU München (DGFI-TUM), Germany); Wolfgang Bosch (Deutsches Geodätisches Forschungsinstitut der TU München (DGFI-TUM), Germany)

Event: 2015 Ocean Surface Topography Science Team Meeting

Session: The Geoid, Mean Sea Surfaces and Mean Dynamic Topography

Presentation type: Type Poster

In order to validate dynamic ocean topography (DOT) data, derived from current satellite altimetry measurements and high-accurate Earth gravity field models, we perform a comparison with in-situ velocity measurements. Our instantaneous DOT (iDOT) is based on the “profile-approach” (Bosch & Savcenko, 2010 and Bosch et al., 2013) estimating so-called iDOT profiles along individual altimeter ground tracks which allows the monitoring of temporal variations of the DOT on spatial scales, close to meso-scale structures.
For the intended pointwise comparison we correct the in-situ surface velocity data provided by surface drifters and ARGO floats for wind and Ekman drift. Furthermore, we convert the iDOT profiles to geostrophic velocity vectors by using the geostrophic equations and interpolate them to the individual in-situ positions. Both velocity fields agree quite well with the majority of the differences being smaller than 0.15 m/s. However, the interpolation method causes a smoothing of the iDOT data and yields about two-times smaller geostrophic velocities than the in-situ measurements. It can be underlined that the interpolation and the related undesired smoothing constitute a limiting factor for the consistency of both velocity fields.
In the present investigation we conduct a sensitivity analysis quantifying the impact of the smoothing to the occurring scaling factor by modifying the temporal and spatial resolution parameters within the interpolation. Results are presented for a chosen study area containing strong western boundary currents and different periods.


Poster show times:

RoomStart DateEnd Date
Grand Ballroom Foyer Thu, Oct 22 2015,11:00 Thu, Oct 22 2015,18:00
Felix Müller
Deutsches Geodätisches Forschungsinstitut der TU München (DGFI-TUM)