Post on 01-Apr-2015
transcript
ECCO-2 and NASA Satellite Missions
Lee-Lueng Fu
Jet Propulsion Laboratory
January 22-23, ECCO-2 Meeting
A snapshot of sea surface height anomalies from T/P and ERS altimeters
SSH wavenumber spectra (Ducet et al. 2000)
T/P along-track
T/P-ERS mapped
T/P mapped
Overlapping at 150 km
Spatial scales of the AVISO T/P-ERS merged data
Small-scale Variability of the Ocean Unresolved by Nadir-looking Altimeter
100 km
ground tracks of Jason (thick) and T/P (thin) Tandem Mission
100 km scale eddies resolvable by WSOA
10 km scale eddiesResolvable by HM
41.9º N
42.5º N
< 10 km
< 10 km
Coastal currents have scales less than 10 km
< 10 km
Observations made by ADCP offshore from the US
West CoastT. Strub
h ~ 5 cm v ~ 50 cm/sec
McWilliams (2006)
Sub-mesoscale variability
Sub-mesoscale processes are poorly observed but important to the understanding of the dissipation mechanism of ocean circulation.
Radius of deformation
Radius of deformation
Altimetry SSH wavenumber spectrum
Wavenumber (cycles/km)
Pow
er d
ensi
ty (
cm2 /
cycl
es/k
m)
Noise level of HM for 2 cm measurement noise at 2 km resolution
Jason pass 132 (147 cycle average)
Stammer (1997)
T/P
T/P
?
?
Much reduced noise floor will enable the study of the spectrum at sub-mesoscales which have not been well resolved from existing data.
= 1cm/km(or 0.4 cm/7km)
= 2cm/2km (or 1 cm/7km)
= 2cm/7km
For the three cases, velocity error is reduced from 7.8 to 3.6, 1.3 cm/sec at 25 km resolution;
or 27, 15, 5 cm/sec at 10 km resolution
Wavenumber (cyc/km)
Vel
ocit
y er
ror
(cm
/s)2
/ cyc
/km
Geostrophic velocity error spectrum100 50 25 km
k -2 spectrum
A Global Hydrosphere MapperA SAR interferometry radar altimeter Near-global coverage with
16-day repeat orbit
• Same technique as WSOA – radar interferometry• Use of SAR to enhance the along-track resolution• 2 cm measurement precision at 2 km resolution• 1 micro-radian precision in mean sea surface slope at 2 km resolution • No data gap near the coast
8
7
6
5
4
3
2
1 Nu
mb
er o
f O
bse
rvat
ion
Wide swath altimetry has been proposed as a surface water and ocean topography (SWOT) mission and favorably endorsed by the NRC Decadal
Survey for a possible new mission in the time frame of 2013-2016.