Short presentation of SKIM Presentation January 2017 CITATIONS - - PDF document

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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/312536222 Short presentation of SKIM Presentation January 2017 CITATIONS READS 0 320 1 author: Fabrice Ardhuin University of

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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/312536222

Short presentation of SKIM

Presentation · January 2017

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320

1 author: Some of the authors of this publication are also working on these related projects: Cyclone Global Navigation Satellite System View project ESA Climate Change Initiative: Sea State View project Fabrice Ardhuin University of California, San Diego

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The SKIM Team

– https://www.facebook.com/SKIM4EE9 http://tinyurl.com/SKIMonRG

The ocean Surface KInematics Multiscale monitoring mission (SKIM)

A proposal for ESA Earth Explorer 9 : Why and how ?

1.5 km

Picture by S. Lamarche

http://www.umr-lops.fr/Projets/Projets-actifs/SKIM

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  • 1. What is SKIM ?

SKIM combines

  • an « altimeter on steroids » looking straight down (at nadir)

(very high PRF Ka-band radar, 200 MHz bandwidth, SAR unfocused) → very low noise measurements of sea level, wave height, ice freeboard … (the best altimeter ever flown)

  • a novel wave + current spectrometer

This is a real aperture radar with 5 to 7 rotating beams (5 in 2016 design) at 6 and 12° incidence → measurement of full wave spectrum unambiguous in direction, down to 20 m wavelength, 5° resolution + wind vector → companion to Sentinel 1 : wave bias correction on total ocean surface currents (single component, error goal < 20 cm/s @ dx= 20 km ) → SKIM alone : total ocean surface vector currents (error goal < 30 cm/s on each component

  • ver a 6 km footprint)

Example of surface Line-of-sight current map, achievable with S1 + SKIM (Chapron et al. JGR 2005)

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  • 2. How does SKIM work ?
  • rotating plate carrying horns
  • pattern of footprints illuminated
  • ver 30 ms.
  • not a full picture but many footprints :

each is 6 km in diameter

  • 1D wave spectrum + radial current on

each footprint.

  • Higher res than 6 km possible with SAR

unfocused

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  • 3. What is SKIM good at ?
  • a. Ocean circulation

SKIM correction on S1 SAR will give total surface current on each pass at high resolution Rouault et al. (JGR 2010). SAR only : many passes averaged High resolution Altimeters : Only geostrophic current resolution ~ 100 km

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  • 3. What is SKIM good at ?
  • b. Ocean circulation

There is no geostrophy at the equator : no currents from altimeters … not a problem for SKIM and SKIM + S1 Envisat (below) → eastward current with a 3 month average S1+SKIM and SKIM → global map every 15 days From Collard et al. (SEASAR 2008)

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  • 3. What is SKIM good at ?
  • b. waves : coastal, wave+current interaction

Measuring much shorter waves than CFOSAT : fraction of resolved wave energy fraction of resolved energy or Stokes drift Measuring shorter waves → measuring Stokes drift

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  • 3. What is SKIM good at ?
  • b. waves : wave-ice interactions

Arctic ice is thinning and shrinking : the Arctic may soon be a giant Marginal Ice Zone in which waves play a big role → urgent to make reliable wave spectra & ice measurements at the ice edge → S1 can be used in the ice (> 10 km from the edge) → SKIM for the open water + leads + near the edge (range bunching on 6° beam) 1-day coverage complementarity with Sentinel 1 (only beam 1 and 6 are shown)

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  • 3. What is SKIM good at ?
  • b. waves : extremes

Measuring detailed directional spectrum → extreme water levels at shoreline A narrow directional spectrum gives larger run-up (Guza and Feddersen JGR 2012)

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  • 3. What is SKIM good at ?
  • b. waves : extremes

Measuring detailed directional spectrum → freak waves estimation Wave spectrum probability of crest height example Freak wave (Fedele et al., Scientific Reports 2016)

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  • 3. What is SKIM good at ?
  • b. solid Earth : microseism sources

SKIM wil measure the full wave spectrum … we still have to verify that we can separate waves in opposite directions. If that works we will directly measure the sources of microseism → considerable improvement in Earth tomography and real time monitoring (Obrebski et al. GRL 2012)

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  • 4. What you can do for SKIM
  • have other ideas of something SKIM can do ?
  • want to use SKIM data one day ?

→ advocate to your national ESA representatives → join the team of PIs or supporters → spread the word about SKIM !

SKIM needs you … without you it will never happen

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  • 4. What you can do for SKIM

More details and updates :

The SKIM Team

https://www.facebook.com/SKIM4EE9 http://tinyurl.com/SKIMonRG

1.5 km

http://www.umr-lops.fr/Projets/Projets-actifs/SKIM

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