User Guides - Sentinel-3 OLCI - Level-2 Water - Sentinel Online
Level-2 Water WRR and WFR
The OLCI Level-2 Water Reduced (OL_2_WRR ) or Full (OL_2_WFR ) Resolution products are outputs from the OLCI Level-2 processor and contain water and atmospheric geophysical products at Full and Reduced Resolution.
The content of these files depends on several switches included in the OLCI configuration parameters. Each geophysical parameter format is only triggered if the corresponding switch is set to '1'. Note that all pixels flagged as cloudy are discarded from OLCI Level-2 processing
The only difference between the OL_2_WFR and OL_2_WRR products is the spatial resolution.
Each product provides the following measurement data files:
- water-leaving reflectance (Rxxx) for all bands except those dedicated to measurement of atmospheric gas. Two types of reflectance are distinguished:
- the BAC reflectance for "Baseline Atmospheric Correction algorithm" (MERIS heritage)
- the AAC reflectance for "Alternative Atmospheric Correction algorithm" (based on a neural network procedure).
- BAC is used for the operational output of the reflectance in this product package but in cases where reflectances are computed and AAC is needed, a setting has been defined in the configuration file to switch between algorithms.
- ocean colour products such as algal pigment (chl_oc4me and chl_nn, in two separated files), Total Suspended Matter (TSM_NN) concentrations and transparency characterisation based on the Diffuse Attenuation coefficient (KD490_M07).
- neural network water-inherent optical properties such as CDM absorption (ADG_443_NN).
- atmosphere by-products such as Photosynthetically Active Radiation (PAR), Aerosol Optical Depth /Aerosol Angstrom exponent (gathered in one file and noted respectively as T865 and A865) and Integrated Water Vapour (IWV) column. Note that this last variable also contains information for land pixels and is identical to the one included in OL_2_WRR and OL_2_WFR.
- error estimates for all the products.
- Several associated variables are also provided in the annotations data files:
- classification, Water Quality and Science Flags (WQSF). The WQSF file provides information about validity, suspicious quality, cosmetic filling, environment and algorithm status.
- common data such as the ortho-geolocation of land pixels, solar and satellite angles, atmospheric and meteorological data, time stamp or instrument information. These variables are inherited from Level-1B products
Table 1: Description of water and atmospheric geophysical product
|Rxxx||Surface directional reflectance, corrected for
atmosphere and sun specular reflection
|dimensionless||all except Oa13, Oa14, Oa15, Oa19 and Oa20|
|chl_oc4me and chl_NN||Chlorophyll-a concentration, computed
using "OC4Me" or Neural Network algorithms
|mg (chl a) m-3||- Oa3 to Oa6
- Oa1-Oa12, Oa16, Oa17,Oa18 and Oa21
|TSM_NN||Total suspended matter concentration.||g.m-3||Oa1-Oa12, Oa16, Oa17, Oa18 and Oa21|
|KD490_M07||Diffuse attenuation coefficient for
down-welling irradiance, at 490 nm.
|m-1||Oa4 and Oa6|
|ADG_443_NN||Absorption of coloured detrital and dissolved material at 443 nm.||m-1||Oa1, Oa12, Oa16, Oa17, Oa21|
|PAR||Quantum energy flux from the sun in the
spectral range 400-700 nm.
|T865 and A865||Aerosol load, expressed in optical depth
at a given wavelength (865 nm) and
spectral dependency of the aerosol optical depth, between 779 and 865 nm.
|dimensionless||Oa5, Oa16 and Oa17|
|IWV||Integrated Water Vapour column||kg.m-2||Oa18, Oa19|