Level-2 consists of geolocated geophysical products derived from Level-1. Level-2 Ocean (OCN) products for wind, wave and currents applications may contain the following geophysical components derived from the SAR data:
- Ocean Wind field (OWI)
- Ocean Swell spectra (OSW)
- Surface Radial Velocity (RVL)
The availability of components depends on the acquisition mode. The metadata referring to OWI are derived from an internally processed GRD product, the metadata referring to RVL (and OSW, for SM and WV mode) are derived from an internally processed SLC product.
The OWI component is a ground range gridded estimate of the surface wind speed and direction at 10 m above the surface, derived from SM, IW or EW modes.
Figure 1: Surface Wind measurement (OWI): Example of SAR wind measurement over Gibraltar (funnelling effect) - Copernicus Sentinel data (2017)
The OSW component is a two-dimensional ocean surface swell spectrum and includes an estimate of wind speed and direction per swell spectrum. The OSW component provides continuity measurement of SAR swell spectra at C-band.
Figure 2: Swell inversion (OSW): Example of ocean wave spectrum presenting 2 swell partitions - Copernicus Sentinel data (2016)
The OSW is generated from Stripmap and Wave modes only and is not available from the TOPSAR IW and EW modes. For Stripmap mode, there are multiple spectra derived from the Level-1 SLC image. For Wave mode, there is one spectrum per vignette.
The RVL surface radial velocity component is a ground range gridded difference between the measured Level-2 Doppler grid and the Level-1 calculated geometrical Doppler. The RVL component provides continuity of the ASAR Doppler grid.
Figure 3: Surface Radial Velocity (RVL): Doppler anomaly over Irma Hurricane (7 September 2017) - Copernicus Sentinel data (2017)