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.