Chapter 11: Remote sensingA: Acoustic remote sensing (was chapter 9)

B: Geostrophic transport estimates

∫ v dx = 1/fρ0 [ p(x2) – p(x1) ] and with the thermal wind relation this becomes

d/dz ∫ v dx = -g/fρ0 [ ρ(x2) – ρ(x1) ]

Thus density profiles at the end points allow to obtain

transport ∫ v dxdz .

Bottom pressure gives reference layer velocity fluctuations.

Here: example fromMOVE array

Total geostrophic NADW transport variability

C: Satellites (and aircraft)(most figures from Summerhayes&Thorpe “Oceanography: an illustrated guide

Spectrum used: visible to microwave, for microwaves have passive and active sensors

Non-scanning versus scanning

Geostationary versus orbiting

Space-time scales

SST observations

Ocean color observations

Synthetic aperture radar (SAR) observations

SAR example

SAR example

Waves and winds (scatterometer)

Altimetry

After the success of SEASAT, the newplanned altimetry missions were adustedto best complement the in-situ observations.Topex/Poseidon (T/P) was essentially designed for WOCE.

Rationale:• cm-accuracy sea-surface height • geostrophic surface flow relative to geoid• heat storage from large-scale steric effect• variability from 20-10000km, 20days-10years

Challenges and limitations:• geoid insufficient at <3000km • aliasing of tides at 62, 173,... days• aliasing of high-frequ. wind-forced variability• extrapolation to ocean interior• no coverage in polar (and ice-covered) regions• land motion of tide gauges for SL rise

Example result: extremely active time-dependence of the circulation (barotropic, baroclinic current systems,eddy motions, etc)

Quantified SSH and slope variance on all space/time scales globally

(C. Wunsch)

(D.Stammer)

Eddy contribution tomeridional heat flux:

Other results/achievements:• open-ocean tides measured globally to 2-3cm• surface heat-flux estimates on basin-scales from storage• observation of interannual variability (ENSO, circumpolar wave, etc)• kinetic energy of geostrophic currents in agreement with moorings• eddy energy helped to demonstrate that models need 0.1° resolution• agreement of T/P currents and ADCP data to 3-5cm/s• global test of Rossby wave speeds• global SL rise (calibrated with tide gauges) accurate to 0.5mm/yr• transports of baroclinic current systems (variability)• drove advances in earth´s gravity field• drove most of the work in assimilation• many more.....

(D. Stammer)

Missions at:http://airsea-www.jpl.nasa.gov/mission/missions.html(OLD) now see seperate ppt file.....

More about altimetry at:http://topex-www.jpl.nasa.gov/www.aviso.oceanobs.com/en/altimetry/index.html

More about scatterometer athttp://winds.jpl.nasa.gov/

General satellite missionswww.aviso.oceanobs.com/

Some sensor types/names:

Scatterometers: NSCAT (on Japanese ADEOS), QuickScat, SeaWinds (on ADEOS-II), ASCAT. Deliver vector wind (stress), sea ice, iceberg drift.

Radars: altimeter, SAR

Radiometer: AVHRR (advanced very high resolution radiometer), has several IR bands, can be used to estimate absorption in atmosphere, gives SST; Also in microwave now – SMMR (scanning multi-channel microwave radiometer), passive, also yields ice cover and humidity

SSM/I: special sensor microwave imager, gives only wind speed (not direction), 4 bands, precipitation

CZCS: coastal zone color scanner (on Nimbus satellite), many visible channels

More neat stuff, e.g. “Iridium flares” atwww.heavens-above.com/

GRACE gravity mission

See also:

www.eohandbook.com

And

www.esa.int/esaEO/index.html

Overview over some satellite-derived products: http://podaac.jpl.nasa.gov/http://coastwatch.pfeg.noaa.gov/coastwatch/CWBrowser.jsp

Altimetry:AVISO: http://www.aviso.oceanobs.com/

http://las.aviso.oceanobs.com/las/servlets/dataset/ftp://ftp.cls.fr/pub/oceano/AVISO/SSH/duacs/

Ocean color and SST (MODIS, SeaWIFS, ...) http://oceancolor.gsfc.nasa.gov/

Ocean surface currents (using wind, altimetry:) http://www.oscar.noaa.gov/(from sequential satellite imagery:) http://ccar.colorado.edu/research/cali/

GRACE gravimetryhttp://op.gfz-potsdam.de/grace/http://podaac.jpl.nasa.gov/DATA_CATALOG/graceinfo.html

Satellite Data Websites:

altimetry

Altimetry and ARGO

Sea surface height (SSH) consists of - the steric (dynamic height Hdyn) contribution of T and S - a barotropic flow component (reference level pressure Pref)

Symbolically SSH = Pref + Hdyn = SSH’ + SSH

Altimetry has good spatial and temporal coverage but cannot determine

- steric and non-steric components- mean SSH field (relative to geoid)- T and S contributions (spiciness)- interior structure (vertical distribution) of Hdyn

ARGO data can help resolve these issues

altimetryFloat profiles

Symbolically SSH = Pref + Hdyn = SSH’ + SSH

scatter is a measurefor non-stericcontributions(plus errors)

altimetric SSH‘ vs in-situ H‘dyn

Compare SSH‘ and float H‘dyn :

large barotropiccontributions athigh latitudes

Correlation vs latitude

(from P.-Y. Le Traon)

altimetryFloat profiles

deeptrajectories

residual

Symbolically SSH = Pref + Hdyn = SSH’ + SSH

Deep mean flow (pref) from float trajectories :

(from R.Davis)