Minimize 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:
    1. the BAC reflectance for "Baseline Atmospheric Correction algorithm" (MERIS heritage)
    2. 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 water 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

Variables Description Units Input Bands
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 and Oa6
- Oa1-Oa12, Oa16, Oa17 and Oa21
TSM_NN Total suspended matter concentration. g.m-3 Oa1-Oa12, Oa16, Oa17 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.
µEinstein.m-2. s-1 -
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