Geoscience Reference
In-Depth Information
Table 1 Summary of environmental correction
Correction/model
Editing (m)
Description
Min
Max
Orbit/gravity field
All satellites: EIGEN GL04C
ERS: DGM-04/D-PAF
Dry troposphere
-2.4
-2.1
All satellites: Atmospheric pressure grids
Wet troposphere
-0.6
0.0
All satellites: Radiometer measurement
Ionosphere
-0.4
0.04
All satellites: Smoothed dual-freq,
ERS/POSEIDON: NIC08
Dynamic atmosphere
-1.0
1.0
All satellites: MOG2D
Ocean tide
-5.0
5.0
All satellites: GOT4.7
Load tide
-0.5
0.5
All satellites: GOT4.7
Solid earth tide
-1.0
1.0
Appplied (Elastic response to tidal potential)
Pole tide
-0.1
0.1
Apllied (Tide produced by Polar Wobble)
Sea state bias
-1.0
1.0
All satellites: CLS non parametric
ERS/POSEIDON: BM3/BM4 parametric
Reference
-1.0
1.0
DNS08 mean sea surface
Engineering flag
Applied
Applied reference frame biases
(cm)
JASON-1:-4.8, ERS-1: +3.4, ERS-2: +7.3,
ENVISAT: +5.2, JASON-2: +15.9,
POSEIDON: -1.5, TOPEX: Reference frame
3 Estimation of Geostrophic Current
Satellite altimetry is one of the promising techniques to understand the ocean
surface currents. The geostrophic currents are proportional to the slope of the
topography, a quantity that can be measured by satellite altimeters if the geoid is
known. Thus, after obtaining the gridded SLA fields as explained in
Sect. 2.1
and
assuming geostrophic balance, the geostrophic current is computed from the
absolute dynamic topography using the following equation (Benny et al.
2008
;
Hwang and Chen
2000
; Wahr et al.
2002
;
f ¼ SLA
þ
MDT
u ¼
g
f
o
f
oy
v ¼
g
f
o
f
ox
f ¼ 2Xsin
ðÞ
where f is the absolute dynamic topography, u and v are the eastward and
northward velocity components of sea surface geostrophic current, g is the local
acceleration due to gravity, f is the Coriolis parameter with X being the earth
rotational rate (7.292115 9 10
-5
), u is the latitude, and x and y are the local
rectangular coordinates. Since the geostrophic balance is not valid near the equator
where Coriolis force is almost zero, the surface geostrophic current is not esti-
mated between 2N and equator.
