Geoscience Reference
In-Depth Information
tides, ocean tide loading, pole tide, electromagnetic bias and inverse barometer
correction.
Homogeneous and cross-calibrated sea surface height (SSH) data sets are
required to merge multi-satellite altimeter missions. Thus, crossover adjustment
has been performed for the integrated data processing for multi-satellite missions.
In this study, only crossovers between ERS-class (ERS and ENVISAT) and
TOPEX-class satellites (TOPEX, POSEIDON and JASON) has been considered
and not those between themselves. Besides that, the area used for the crossover
minimization is defined much larger than the study area to have sufficient cross-
over. ERS-class and TOPEX-class data are merged and gridded into 0.2590.25
latitude/longitude bins using Inverse Distance Weighting (IDW) Interpolation
method. The gridding involved both temporal and spatial weighing. Then, the SLA
data are smoothed using Gaussian filtering to filter out noise in the data. The
summary of environmental corrections applied in altimeter data processing is
shown in the Table
1
.
2.2 Mean Dynamic Topography
The SLA derived from the RADS are combined with 1992-2002 Mean Dynamic
Ocean Topography (Maximenko et al.
2009
) to obtain absolute dynamic topog-
raphy. This Mean Dynamic Ocean Topography model has been developed using
joint data of satellite altimetry, near-surface drifters, National Centre for Envi-
ronmental Prediction (NCEP) wind and Gravity Recovery and Climate Experiment
(GRACE). More information about the MDT used in this study can be found at
2.3 Argos-Tracked Ocean Surface Drifters
Observational data of Argos-tracked ocean surface drifters are widely used to
reveal basic features of surface current pattern in the surface and subsurface layers
(Yang et al.
2002
). The current measurement error by drifter is *5 cm/s, and the
locating error is *1 km (Su et al.
2002
). Thus, to evaluate the absolute geo-
strophic current pattern obtained in this study, it is compared with the tracks of a
satellite-tracked drifting buoy ID 49696. The drifter data is provided by the Marine
Environmental
Data
Services
(MEDS)
of
Canada
