Chapter 11: Remote sensing A: Acoustic remote sensing (was chapter 9)‏ B: Geostrophic transport estimates ∫ v dx = 1/fρ 0 [ p(x 2 ) – p(x 1 ) ] and with the thermal wind relation this becomes d/dz ∫ v dx = -g/fρ 0 [ ρ(x 2 ) – ρ(x 1 ) ] Thus density profiles at the end points allow to obtain transport ∫ v dxdz. Bottom pressure gives reference layer velocity fluctuations. Here: example from MOVE 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

Waves and winds (scatterometer)‏

Altimetry After the success of SEASAT, the new planned altimetry missions were adusted to 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 km, 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 to meridional 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: (OLD) now see seperate ppt file..... More about altimetry at: More about scatterometer at General satellite missions

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” at GRACE gravity mission

See also: And

Overview over some satellite-derived products: Altimetry: AVISO: ftp://ftp.cls.fr/pub/oceano/AVISO/SSH/duacs/ Ocean color and SST (MODIS, SeaWIFS,...) Ocean surface currents (using wind, altimetry:) (from sequential satellite imagery:) GRACE gravimetry Satellite Data Websites:

altimetry Altimetry and ARGO Sea surface height (SSH) consists of - the steric (dynamic height H dyn ) contribution of T and S - a barotropic flow component (reference level pressure P ref )‏ Symbolically SSH = P ref + H dyn = 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 H dyn ARGO data can help resolve these issues

altimetry Float profiles Symbolically SSH = P ref + H dyn = SSH’ + SSH scatter is a measure for non-steric contributions (plus errors)‏ altimetric SSH‘ vs in-situ H‘ dyn Compare SSH‘ and float H‘ dyn : large barotropic contributions at high latitudes Correlation vs latitude (from P.-Y. Le Traon)‏

altimetry Float profiles deep trajectories residual Symbolically SSH = P ref + H dyn = SSH’ + SSH Deep mean flow (p ref ) from float trajectories : (from R.Davis)‏