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Remote sensing of
oceanic mesoscale processes
Hui Shen, Will Perrie, Catherine Johnson
Bedford Institute of Oceanography
Fisheries and Oceans Canada
Email: [email protected]'19
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Outline
A brief introduction of mesoscale oceanic processes
Remote sensing techniques for mesoscale processes
observations
Altimeter, Radiometer, HF radar, high resolution
spectrometer, and Synthetic Aperture Radar (SAR)
Mesoscale feature measurements by SAR
Internal waves in Gulf of Maine
Eddies in Labrador Sea
Summary and future perspectives2019-05-31OceanPredict'19
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Oceanic mesoscale processes
Mesoscale:
days to weeks
~100 km
OceanPredict'19
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Oceanic mesoscale processes
Mesoscale:
days to weeks
~100 km
Processes
Eddies
Fronts
Internal waves
2019-05-31OceanPredict'19
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Mesoscale:
days to weeks
~100 km
Importance:
Energy cascade
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Oceanic mesoscale processes
Oceanic mesoscale processes
Mesoscale:
days to weeks
~100 km
Importance:
Energy cascade
Ocean mixing
Vertical mass transport
Driver of local ecology system
Etc. OceanPredict'19
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Faghmous et al., 2011
2019-05-31OceanPredict'19
7Oceanic mesoscale processes
Mesoscale:
days to weeks
~100 km
Importance:
Energy cascade
Ocean mixing
Vertical mass transport
Driver of local ecology system
Etc.
Observation of mesoscale processes
Eddy: ship, transect, buoy vs. eddy, isw.
Advantage; most reliable first hand observation,
temporal resolution
Disadvantage: spatial resolution, miss
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Indian Ocean GEOTRACES cruise sections ©
Remote sensing of mesoscale processes
Altimeter
SSHA
Barotropic balance – map
Warm eddy –
Cold eddy –
Operational example:
GlobCurrent®
Drushka et al. SWOT Tseng et al., 2010
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Remote sensing of mesoscale processes
Altimeter
SSHA
Radiometer
SST
Spectrometer
Ocean color
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Remote sensing of mesoscale processes
Altimeter
SSHA
Radiometer
SST <ageostropic >
HF radar
Current vector
IMOS
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High resolution imaging
and its application to mesoscale observations
How high
~Meter resolution
Remote sensing mechanism
Ocean color - optical remote sensing
Surface roughness – SAR + optical
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SAR-Synthetic Aperture Radarmicrowave band (all day, all weather, no clouds)
active monitoring
sensitive to roughness (cm)
SAR sees the capillary waves!
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Optical remote sensing - radiometry
SPIE
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High resolution imaging
and its application to mesoscale observations
Case 1
Internal waves in Gulf of Maine
Sentinel-2 2018/08/102019-05-31OceanPredict'19
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How remote sensing sees ISWs from surface
Alpers theory (Nature
1980)
Coherent modulation
on surface capillary
waves, was sensitive to
the remote sensing
Eyes are blurred /
confused by ocean
color
Ocean surface features
(bubbles, breakings)Field measurement in SCS
2009.05 (Courtesy: P. Hu) 2019-05-31OceanPredict'19
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ISW and Fish school
TerraSAR-X image acquired on 23 June 2008 at 22:25 h
UTC over Cape Cod Bay, showing two large ISW trains
emanating from Race Point Channel with bathymetry
overlaid on the SAR image.
Fig. Internal wave train from acoustic backscatter
on 1 August 2008. Backscatter arising with the
internal wave (16:37 h) was identified as sand
lance. [Pineda et al., 2015 JGR]
OceanPredict'19
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High resolution imaging
and its application to mesoscale processes observations
Internal waves in Gulf of Maine
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High resolution imaging
and its application to mesoscale observations
Internal waves in Gulf of Maine
FVCOM [Chen et al. 2003] Shen, H., W. Perrie, C. Johnson. Predicting internal
solitary waves in Gulf of Maine. In preparation
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Internal wave footprints
Properties of the ISW:
Speed
Wavelength
Amplitude
Mixed Layer Depth
(MLD)
Stratification
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High resolution imaging
and its application to mesoscale observations
2. Labrador Sea Eddies
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High resolution imaging
and its application to mesoscale observations
Labrador Sea Eddies
2010-02-25
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Deep convection within an eddy
Preconditioning
~ large-scale (order of 100 km)
Deep convection
Localized, intense plumes (~1 km)
Lateral exchange
Baroclinic instability, eddies (~10 km)
Re-stratification
OPEN-OCEAN DEEP CONVECTION
Marshall and Scott, 1999
Legg et al., 1998
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Deep convection within an eddy
Preconditioning
~ large-scale (order of 100 km)
Deep convection
Localized, intense plumes (~1 km)
Lateral exchange
Baroclinic instability, eddies (~10 km)
Re-stratification
OPEN-OCEAN DEEP CONVECTION
Marshall and Scott, 1999
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High resolution imaging
and its application to mesoscale observations
Labrador Sea Eddies – Irminger Ring
Kawasaki & Sasumi, 2014
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Summary and future perspectives
Remote Sensing provides unique measurements to
oceanic mesoscale processes
Morden high reolsuiton imaging measurement provide
detailed features of mesoscale processes
High resolution remote sensing data was used to study
the internal waves in Gulf of Maine and eddies in
Labrador Sea
Challenge remains to take the fully advantage of the
high spatial resolution, for bettering understanding of
oceanic processes.
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Thank you for your attention
Comments?
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St. Laurent & Garret,
2002
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Model validation?
Chanut et al. (2008)
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![Oceanic mesoscale eddies as revealed by Lagrangian ...objective (i.e, frame-independent) eddy boundary definition [Haller, 2001; Green et al., 2007], and is exploited here to unambiguously](https://img.pdfslide.us/doc/110x75/5f8a5c324adaac6ea153f8d9/oceanic-mesoscale-eddies-as-revealed-by-lagrangian-objective-ie-frame-independent.jpg)
