.. |vspace| raw:: latex
\vspace{5mm}
.. |br| raw:: html
.. index:: S3-SNOW Products
.. _s3snow_products:
====================
The S3-SNOW Products
====================
Overview
========
This section will give an overview of all input, intermediate, optional and final products used and generated by the SNAP
S3-SNOW processors introduced in the previous chapter.
.. index:: Input Products
Input Products
==============
OLCI L1b TOA Radiance Product
-----------------------------
Both reduced and full resolution OLCI L1b TOA radiance products can
be used as input data. Tables 3.1 to 3.4 give an overview of
OLCI L1b bands, tie point grids and L1b flag coding, respectively. A more detailed description of the OLCI
standard L1b product is given in [`3 `_].
|vspace| |br|
.. _olci_bands_l1b:
.. table:: OLCI bands in L1b product
+----------------------------------+---------------------+------------+---------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+==================================+=====================+============+=================================+
| Oa_radiance; n=01,..,21 | mW/(m^2*sr*nm) | float32 | TOA radiance in band |
+----------------------------------+---------------------+------------+---------------------------------+
| lambda0_band_; n=01,..,21 | nm | float32 | Central wavelength in band |
+----------------------------------+---------------------+------------+---------------------------------+
| FWHM_band_; n=01,..,21 | nm | float32 | Bandwidth in band |
+----------------------------------+---------------------+------------+---------------------------------+
| solar_flux_band_; n=01,..,21 | mW/(m^2*nm) | float32 | Solar flux in band |
+----------------------------------+---------------------+------------+---------------------------------+
| quality_flags | dl (flag band) | int32 | L1b quality flags |
+----------------------------------+---------------------+------------+---------------------------------+
| altitude | m | float32 | Altitude |
+----------------------------------+---------------------+------------+---------------------------------+
| latitude | degrees | float32 | Latitude |
+----------------------------------+---------------------+------------+---------------------------------+
| longitude | degrees | float32 | Longitude |
+----------------------------------+---------------------+------------+---------------------------------+
| frame_offset | dl | float32 | Resampling frame offset |
+----------------------------------+---------------------+------------+---------------------------------+
| detector_index | dl | float32 | Detector index |
+----------------------------------+---------------------+------------+---------------------------------+
|vspace| |br|
.. _olci_instrument_channels:
.. table:: OLCI instrument channels.
+-------------------------------+------------------------------+
| **Channel** | **Wavelength** |
+===============================+==============================+
| 1 | 400.0 |
+-------------------------------+------------------------------+
| 2 | 412.5 |
+-------------------------------+------------------------------+
| 3 | 442.5 |
+-------------------------------+------------------------------+
| 4 | 490 |
+-------------------------------+------------------------------+
| 5 | 510 |
+-------------------------------+------------------------------+
| 6 | 560 |
+-------------------------------+------------------------------+
| 7 | 620 |
+-------------------------------+------------------------------+
| 8 | 665 |
+-------------------------------+------------------------------+
| 9 | 673.75 |
+-------------------------------+------------------------------+
| 10 | 681.25 |
+-------------------------------+------------------------------+
| 11 | 708.75 |
+-------------------------------+------------------------------+
| 12 | 753.75 |
+-------------------------------+------------------------------+
| 13 | 761.25 |
+-------------------------------+------------------------------+
| 14 | 764.375 |
+-------------------------------+------------------------------+
| 15 | 767.5 |
+-------------------------------+------------------------------+
| 16 | 778.75 |
+-------------------------------+------------------------------+
| 17 | 865 |
+-------------------------------+------------------------------+
| 18 | 885 |
+-------------------------------+------------------------------+
| 19 | 900 |
+-------------------------------+------------------------------+
| 20 | 940 |
+-------------------------------+------------------------------+
| 21 | 1020 |
+-------------------------------+------------------------------+
|vspace| |br|
.. _olci_tpgs:
.. table:: OLCI tie point grids in L1b product.
+-----------------------------+----------+--------------+-----------------------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+=============================+==========+==============+===============================================+
| TP_latitude | deg | float32 | Latitude of the tie points |
+-----------------------------+----------+--------------+-----------------------------------------------+
| TP_longitude | deg | float32 | Longitude of the tie points |
+-----------------------------+----------+--------------+-----------------------------------------------+
| SZA | deg | float32 | Sun zenith angle |
+-----------------------------+----------+--------------+-----------------------------------------------+
| SAA | deg | float32 | Sun azimuth angle |
+-----------------------------+----------+--------------+-----------------------------------------------+
| OZA | deg | float32 | View zenith angle |
+-----------------------------+----------+--------------+-----------------------------------------------+
| OAA | deg | float32 | View azimuth angle |
+-----------------------------+----------+--------------+-----------------------------------------------+
| horizontal_wind_vector_1 | m/s | float32 | Zonal wind component |
+-----------------------------+----------+--------------+-----------------------------------------------+
| horizontal_wind_vector_2 | m/s | float32 | Meridional wind component |
+-----------------------------+----------+--------------+-----------------------------------------------+
| total_columnar_water_vapour | kg/m^2 | float32 | Total column of water vapour |
+-----------------------------+----------+--------------+-----------------------------------------------+
| sea_level_pressure | hPa | float32 | Mean sea level pressure |
+-----------------------------+----------+--------------+-----------------------------------------------+
| ozone | kg/m^2 | float32 | Total ozone |
+-----------------------------+----------+--------------+-----------------------------------------------+
| humidity | % | float32 | Relative humidity |
+-----------------------------+----------+--------------+-----------------------------------------------+
|vspace| |br|
.. _olci_l1b_flag_coding:
.. table:: OLCI L1b flag coding.
+-------------------------------+------------------------------+-------------------------------+
| **Bit** | **Flag** | **Description** |
+===============================+==============================+===============================+
| 0-20 | saturated_Oa<21-nn> | Band is saturated |
+-------------------------------+------------------------------+-------------------------------+
| 21 | dubious | Pixel is cosmetic |
+-------------------------------+------------------------------+-------------------------------+
| 22 | sun_glint_risk | Pixel has been duplicated |
+-------------------------------+------------------------------+-------------------------------+
| 23 | duplicated | Pixel has glint risk |
+-------------------------------+------------------------------+-------------------------------+
| 24 | cosmetic | Pixel is suspect |
+-------------------------------+------------------------------+-------------------------------+
| 25 | invalid | Pixel is over land, |
+-------------------------------+------------------------------+-------------------------------+
| 26 | straylight_risk | Pixel is bright |
+-------------------------------+------------------------------+-------------------------------+
| 27 | bright | Pixel is part of a coastline |
+-------------------------------+------------------------------+-------------------------------+
| 28 | tidal_region | Pixel is suspect |
+-------------------------------+------------------------------+-------------------------------+
| 29 | fresh_inland_water | Pixel is over land, |
+-------------------------------+------------------------------+-------------------------------+
| 30 | coastline | Pixel is bright |
+-------------------------------+------------------------------+-------------------------------+
| 31 | land | Pixel is part of a coastline |
+-------------------------------+------------------------------+-------------------------------+
|vspace| |br|
OLCI L1b Bottom-of-Rayleigh Reflectances (BRR) Product
------------------------------------------------------
As an alternative to the OCLI L1b radiance products, the Snow Properties Processor also accepts as input
BRR products which have been generated in a pre-processing step using the
SNAP Rayleigh Correction Processor. This processor can be accessed from the SNAP Desktop application as shown in
:numref:`rayleigh_in_snap`.
.. _rayleigh_in_snap:
.. figure:: pix/rc_in_snap.png
:align: center
:scale: 80 %
Access to Rayleigh Correction Processor in SNAP Desktop.
The Rayleigh Correction Processor is a SNAP build-in component. For a detailed description see the corresponding SNAP
help documentation. For BRR products to be used with the Snow Properties Processor, BRR for spectral bands 1, 6, 17 and 21
(400nm, 560, 865 and 1020nm) must be generated, and in addition the BRRs for all other spectral bands of interest.
In :numref:`rayleigh_params`, the parameter settings to generate
BRR in bands 1, 6, 17 and 21, and in addition bands 9 and 10, are shown.
.. _rayleigh_params:
.. figure:: pix/rc_params.png
:align: center
:scale: 80 %
Rayleigh Correction: parameters for the generation of BRR in bands 1, 5, 17 and 21, and in addition in bands 9 and 10.
The bands in the resulting BRR product are listed in Table 3.5.
.. _rc_bands:
.. table:: Bands in BRR product
+-------------------------+---------------------+------------+----------------------------------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+=========================+=====================+============+==========================================================+
| rBRR_01 | dl | float32 | Bottom-of-Rayleigh reflectance for band 1 (400nm) |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| rBRR_05 | dl | float32 | Bottom-of-Rayleigh reflectance for band 5 (510nm) |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| rBRR_17 | dl | float32 | Bottom-of-Rayleigh reflectance for band 17 (865nm) |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| rBRR_21 | dl | float32 | Bottom-of-Rayleigh reflectance for band 21 (1020nm) |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| rBRR_ | dl | float32 | Bottom-of-Rayleigh reflectance in band (optional) |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| quality_flags | dl | int32 | L1b quality flags |
+-------------------------+---------------------+------------+----------------------------------------------------------+
Intermediate and Optional Products
==================================
SNAP IdePix Classification Product
----------------------------------
The IdePix classification product is the result of the pixel classification performed on the OLCI L1b
product. In return, the IdePix product can be used as optional input for Snow Properties Processor.
The IdePix OLCI version for S3-SNOW provides an 'extended' classification product containing the bands
listed in Table 3.6.
.. _idepix_bands:
.. table:: Bands in IdePix pixel classification product
+-------------------------+---------------------+------------+----------------------------------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+=========================+=====================+============+==========================================================+
| Oa21_reflectance | dl | float32 | TOA reflectance for band 21 |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| trans_13 | dl | float32 | Rectified and desmiled transmission for band 13 |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| press_13 | hPa | float32 | Pressure for band 13 neglecting scattering |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| surface_13 | dl | float32 | Rectified transmission for band 13 neglecting scattering |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| surface_pressure | hPa | float32 | Pressure at altitude of the surface |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| altitude | m | float32 | Altitude of the surface (from DEM or L1b product) |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| cloud_over_snow | dl | float32 | Mask band indicating if there is cloud over snow |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| pixel_classif_flags | dl | int16 | Standard IdePix classification flag band |
+-------------------------+---------------------+------------+----------------------------------------------------------+
| quality_flags | dl | int32 | L1b quality flags |
+-------------------------+---------------------+------------+----------------------------------------------------------+
The IdePix OLCI classification flag coding is given in Table 3.7.
.. _idepix_flagcoding:
.. table:: Bands in IdePix pixel classification product
+------------+------------------------+-------------------------------------------------------------+
| **Bit** | **Flag** | **Description** |
+============+========================+=============================================================+
| 0 | IDEPIX_INVALID | Pixel is invalid |
+------------+------------------------+-------------------------------------------------------------+
| 1 | IDEPIX_CLOUD | Pixel is either 'cloud sure' or 'cloud ambiguous' |
+------------+------------------------+-------------------------------------------------------------+
| 2 | IDEPIX_CLOUD_AMBIGUOUS | Semi-transparent clouds, or detection is uncertain |
+------------+------------------------+-------------------------------------------------------------+
| 3 | IDEPIX_CLOUD_SURE | Fully opaque clouds with full confidence of detection |
+------------+------------------------+-------------------------------------------------------------+
| 4 | IDEPIX_CLOUD_BUFFER | A buffer of N pixels (user option) around a cloud |
+------------+------------------------+-------------------------------------------------------------+
| 5 | IDEPIX_CLOUD_SHADOW | Pixel is affected by a cloud shadow |
+------------+------------------------+-------------------------------------------------------------+
| 6 | IDEPIX_SNOW_ICE | Snow or ice pixel |
+------------+------------------------+-------------------------------------------------------------+
| 7 | IDEPIX_BRIGHT | Pixel is bright |
+------------+------------------------+-------------------------------------------------------------+
| 8 | IDEPIX_WHITE | Pixel is white |
+------------+------------------------+-------------------------------------------------------------+
| 9 | IDEPIX_COASTLINE | Pixel is part of a coastline |
+------------+------------------------+-------------------------------------------------------------+
| 10 | IDEPIX_LAND | Land pixel |
+------------+------------------------+-------------------------------------------------------------+
O2 Correction Product
---------------------
The O2 correction step is done as part of the IdePix pixel classification. The results of this step are
used by IdePix internally, and no separate products are written in the S3-SNOW processing flow. However, as the
O2 correction is also available as a standalone SNAP plugin with a separate target product, its contents are
listed in Table 3.8 for completeness.
.. _o2corr_bands:
.. table:: Bands in O2 Correction target product
+-------------------------+---------------------+------------+-------------------------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+=========================+=====================+============+=================================================+
| trans_13 | dl | float32 | Rectified and desmiled transmission for band 13 |
+-------------------------+---------------------+------------+-------------------------------------------------+
| press_13 | hPa | float32 | Pressure for band 13 neglecting scattering |
+-------------------------+---------------------+------------+-------------------------------------------------+
| surface_13 | dl | float32 | Rectified transmission for band 13 |
+-------------------------+---------------------+------------+-------------------------------------------------+
| radiance_13 | mW/(m^2*sr*nm) | float32 | TOA radiance in band 13 |
+-------------------------+---------------------+------------+-------------------------------------------------+
Slope Product
-------------
A slope product is the output of the SNAP Slope Processor introduced in chapter :doc:`s3snow_processing_system`.
As mentioned, this is an optional product which is not directly used in the S3-SNOW processing flow.
For completeness, its contents are listed in Table 3.9.
.. _slope_bands:
.. table:: Bands in Slope Processor target product
+-------------------------+---------------------+------------+---------------------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+=========================+=====================+============+=============================================+
| slope | degrees | float32 | Terrain slope |
+-------------------------+---------------------+------------+---------------------------------------------+
| aspect | degrees | float32 | Aspect angle in [0, 360] deg |
+-------------------------+---------------------+------------+---------------------------------------------+
| | m | float32 | altutide band from input product (optional) |
+-------------------------+---------------------+------------+---------------------------------------------+
|vspace| |br|
.. index:: Final Products
Final Snow Properties Product
=============================
The S3-SNOW final product contains various snow properties, depending on the processing paramaters specified by the user.
The maximum number of bands which can be generated is given in Table 3.10.
For more detailed explanations of the physical meaning of the parameters, see [`2 `_].
.. _snowprop_bands:
.. table:: Bands in final S3-SNOW snow properties product
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| **Name in product** | **Unit** | **Type** | **Description** |
+==================================+=====================+============+============================================================+
| albedo_bb_spherical_vis | dl | float32 | Spherical albedo in broadband visible range |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_bb_spherical_nir | dl | float32 | Spherical albedo in broadband near infrared range |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_bb_spherical_sw | dl | float32 | Spherical albedo in broadband shortwave range |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_bb_planar_vis | dl | float32 | Planar albedo in broadband visible range |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_bb_planar_nir | dl | float32 | Planar albedo in broadband near infrared range |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_bb_planar_sw | dl | float32 | Planar albedo in broadband shortwave range |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_spectral_spherical_ | dl | float32 | Spectral spherical albedo in band (max. 21 bands) |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| albedo_spectral_planar_ | dl | float32 | Spectral planar albedo in band (max. 21 bands) |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| rBRR_ | dl | float32 | BRR in band (max. 21 bands) |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| ppa_spectral_ | dl | float32 | PPA in band (max. 21 bands) |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| grain_diameter | mm | float32 | Snow grain diameter |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| snow_specific_area | m^2/kg | float32 | Snow specific surface area |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| ndbi | dl | float32 | Bare ice indicator |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| pollution_mask | dl | float32 | Pollution mask |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| f | 1/mm | float32 | Normalized snow impurity absorption coefficient at 1micron |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| l | mm | float32 | Effective absorption length |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| m | dl | float32 | Absorption Angstrom parameter |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| r_0 | dl | float32 | Reflectance of nonabsorbing snow layer |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| f_rel_err | dl | float32 | Relative error of parameter f |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| l_rel_err | dl | float32 | Relative error of parameter l |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| m_rel_err | dl | float32 | Relative error of parameter m |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| r_0_rel_err | dl | float32 | Relative error of parameter r_0 |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| ndsi | dl | float32 | NDSI |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| ndsi_mask | dl | float32 | NDSI mask for snow identification |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| quality_flags | dl | int16 | L1b quality flags |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
| pixel_classif_flags | dl | int16 | Pixel classification flags |
+----------------------------------+---------------------+------------+------------------------------------------------------------+
|vspace| |br|