C2RCC S2-MSI Processing Parameters |

### Sentinel-2 MSI Processing Parameters

NOTE 1
There are different auxiliary data source for air pressure (at surface level) and ozone.

- TOMSOMI and NCEP data provided by the optional products or by pointing to a directory pre-filled with data products
- ECMWF data contained in the S2 MSI Products
- Constant parameter values

In this order the data is also prioritised. If all sources are specified, first the external data, then the internal and as last option the constant values are used. The impact of the ECMWF data has not yet been validated and should the option should be used with care.

NOTE 2
At the time of the release of this processor the two auxillary variables tco3 and tcwv are swapped. This is considered in the operator by using the description as indicator for the correct data. Even when this is corrected in the S2 reader the processor should still function correctly. See: [SIITBX-497] Names of ECMWF tie-point grids are mixed up

- Valid-pixel expression
  The arithmetic expression defines the pixels which are valid for processing. Pixels which are not valid will be marked as no-data in the target product.
- Salinity
  The value used as water salinity for the scene.
- Temperature
  The value used as water temperature for the scene.
- Ozone
  The value used as ozone if not provided by auxiliary data
- Air Pressure
  The surface air pressure at sea level if not provided by auxiliary data
- Elevation
  The value used as elevation for scene.
- TSM factor
  Conversion factor bpart. (TSM = TSMfac * iop_btot^TSMexp)
- TSM exponent
  Conversion factor bwit. (TSM = TSMfac * iop_btot^TSMexp)
- CHL exponent
  Chlorophyll exponent (CHL = iop_apig^CHLexp * CHLfac)
- CHL factor
  Chlorophyll factor (CHL = iop_apig^CHLexp * CHLfac)
- Threshold rtosa OOS
  Threshold for out of scope of nn training dataset flag for gas corrected top-of-atmosphere reflectances
- Threshold AC reflectances OOS
  Threshold for out of scope of nn training dataset flag for atmospherically corrected reflectances
- Threshold for cloud flag on down transmittance @865
  Threshold for cloud test based on downwelling transmittance @865.
- Atmospheric aux data path
  Path to the atmospheric auxiliary data directory. Use either this or the specified products on the I/O Parameters (ozone, air pressure) tab. If the auxiliary data is not available at this path, the data will automatically be downloaded. More information about the auxiliary data and its handling is provided on the Auxiliary Data Directory page.
- Alternative NN Path
  Path to an alternative set of neuronal nets. Use this to replace the standard set of neuronal nets. For MSI there exits a neural net where ranges of parameters was extended to moderate-to-extreme cases (C2X-Nets). However, this is a parameter which should only used during the development of new neural nets.
- Set of neural nets.
  On of the pre-defined sets of neural nets can be selected. Currently you can select between three different sets.

  Name | Description
  C2RCC-Nets | Standard NNs preferably to be used for eutrophic to mesotrophic water types
  C2X-Nets | Special NNs for high concentrations of suspended material and chlorophyll concentration
  C2X-COMPLEX-Nets | Special NNs for optically complex water types, preferably to be used for inland waters.

- Output AC reflectances as rrs instead of rhow
  Write remote sensing reflectances instead of water leaving reflectances.
- Derive water reflectance from path radiance and transmittance
  Alternative way of calculating water reflectance. Still experimental.
- Use S2 internal ECMWF data, if available
  Specifies if the ECMWF auxiliary data (msl and tco3) from the Sentinel-2 MSi product shall be used. Please have a look at the notes about data priority and reader issue at the page header.
- Output gas corrected TOSA reflectances
  Can be enabled to include the TOSA reflectances in the target product.
- Output TOA reflectances
  Add TOA reflectances to the target product.
- Output gas corrected TOSA reflectances
  Add TOSA reflectances to the target product.
- Output gas corrected TOSA reflectances of auto nn
  Add TOSA reflectances of the autoassociative neural net to the target product.
- Output path radiance reflectances
  Add path radiance reflectances to the target product
- Output downward transmittance
  Add downward transmittance to the target product
- Output upward transmittance
  Add upward transmittance to the target product
- Output atmospherically corrected angular dependent reflectances
  Add atmospherically corrected angular dependent reflectances to the target product
- Output normalized water leaving reflectances
  Add normalized water leaving reflectances to the target product
- Output out of scope values
  Add out of scope to the target product
- Output irradiance attenuation coefficients
  Add irradiance attenuation coefficients to the target product
- Output uncertainties
  Add uncertainties to the target product