CoAuthors

Eric Caubet (Thales Alenia Space, France); Bertrand Chapron (LOPS, Univ. Brest, CNRS, Ifremer, IRD, France); Jean-Claude Lalaurie (CNES, France); Celine Tison (CNES, France); Juliette Lambin (CNES, France); Frederic Dias (University College Dublin, Ireland); Oyvind Breivik (MetNorway, Norway); Ad Reniers (T.U. Delft, The Netherlands); Marion Tissier (T.U. Delft, The Netherlands); Gérald Dibarboure (CLS, France); Rosemary Morrow (LEGOS, France); Fabrice Collard (OceanDataLab, France); Alvise Benetazzo (ISMAR, Italy); Agnieszka Herman (University of Gdansk, Poland); Alexis Mouche (LOPS, Univ. Brest, CNRS, Ifremer, IRD, France)

SKIM is a multi-scale ocean mission looking at interfaces with land & atmosphere, and marginal ice. Propagating over a turbulent ocean, waves can be strongly sensitive to surface currents. This is particularly true in coastal areas where currents combine with shoreline geometry to create a multi-scale pattern of coastal hazards. Coastal exposure to extreme water levels and shoreline erosion are very sensitive to wave directions that are not measured except for a few in situ buoys. Many properties at the air-sea interface are controlled and mixed by ocean waves and then further transported by the total current – not just the geostrophic current accessible from existing and planned altimeter missions. For example, the rapidly emerging research field on ocean microplastics requires information on both the upper ocean vertical mixing induced by waves, and the transport by currents. The community of operational oceanography and marine forecasting will benefit from SKIM through the unprecedented coverage and quality of the wave spectra and current fields that it will return, this has implications for oil fate monitoring and search and rescue. The SKIM mission addresses these challenges by simultaneously bringing full directional wave spectra and surface currents.

SKIM is a high-resolution nadir and off-nadir (6 and 12°) rotating Ka-band altimeter, including Doppler measurement. The very high pulse repetition frequency of 32kHz and bandwidth of 200MHz combine to gives a Doppler accuracy comparable to Sentinel 1 (4Hz vs 2Hz), allowing to resolve horizontal current velocities to 0.1 m/s over a 6 km diameter footprint. Mechanical scanning is done at 3 rotations per minute. Footprints are further resolved at 3 m in range and 400 m in azimuth using an unfocused SAR processing. The surface backscatter and Doppler combined will provide directional wave spectrum down to wavelengths of 20 m, in all wave conditions and a full azimuth coverage – a clear improvement from existing and planned missions. The full spectrum will be measured every 70 km. Some spectral components will be resolved at 10 km or better. Further combination with numerical models will lead to estimations of the wave field properties at resolutions of the order of 5 km.

In this presentation we will review:
- the expected performances of the nadir beam as a high-class Doppler altimeter
- the benefits of a full spectral wave measurement to correct sea state biases
- the relationship between off-nadir Doppler and surface currents and waves
- various possible processing modes including a delta-K analysis
looking at opportunities for science applications in the nearshore, the marginal ice zone and regions of significant wave-current interactions.

More information: https://www.researchgate.net/publication/304452423_sea_Surface_KInematics_Multiscale_monitoring_full_proposal_for_ESA_Earth_Explorer_9
https://www.facebook.com/SKIM4EE9/
http://www.umr-lops.fr/Projets/Projets-actifs/SKIM