Low Resolution SCC L1 Products
==============================

.. warning::
  This section is still under development.
  
  
Introduction
------------

The Single Calculus Chain (SCC) is the standard EARLINET tool to perform
automatic and quality nchecked analysis of raw lidar data. It is
composed by three different modules:

-  ELPP (EARLINET Lidar Pre-Processor)
-  ELDA (EARLINET Lidar Data Analizer)
-  ELDEC (EARLINET Lidar DEpolarization Calibrator)

Whenever an input file containing raw lidar data has been submitted to
the SCC ELPP is automatically ran on it. The ELPP module pre-processes
the raw data performing all the corrections and data handling needed
before the optical retrieval algorithms can be applied by ELDA module.
The ELPP output files contain pre-processed range corrected signals
corrected for instrumental effects as well as atmospheric molecular
parameters calculated from standard model or radiosounding. Typically,
the vertical and temporal resolutions of the pre-processed signals
included in these files is lower than the raw vertical and temporal
resolution as in general time/vertical integration is performed by ELPP
to increase the SNR and allow the calculation of optical products with a
reduced uncertainties. As a consequence the ELPP output files are called
Low Resolution SCC L1 Products. Another SCC module (HiRELPP – High
Resolution EARLINET Lidar Pre-Processor) currently under development
will produce High Resolution SCC L1 Products in which both time and
vertical resolution are kept as higher as possible.

This document provides a detailed description about the structure and
the format of Low Resolution SCC L1 Product as produced by the SCC v4.0.

Low Resolution SCC L1 Product: File format
------------------------------------------

The Low Resolution SCC L1 Products are files in Network Common Data Form
(NetCDF) which is a well known self-describing, machine-independent data
format that support the creation, access, and sharing of array-oriented
scientific data. For more information about NetCDF format:
http://www.unidata.ucar.edu/software/netcdf/.

The NetCDF is a binary format that allows the definition of
multi-dimensional variables of several types (integers, double,
character, etc). For each variable it is possible to define one or more
attributes where to specify variable properties like units, long name,
description, etc.

It is possible to define global attributes which are not related to a
specific variable but to the whole file.

A NetCDF file is composed by four different section:

dimensions
   this section contains all the dimensions used in the definition of
   all the variables included in the NetCDF file

variables
   this section contains all the variables stored in the NetCDF file.
   Each variable is defined as a multi-dimensional array of a specific
   type and with all the dimensions defined in the dimensions section

global attributes
   this section lists all the attributes referring to the whole file. As
   the variable the attributes (global or the one attached to a specific
   variable) can be of different type

data
   in this section the data contained in each variable defined in
   variable section is stored. Attribute values (both global or related
   to a specific variable) are not reported in data section but directly
   in variable or global attribute sections.

Each Low Resolution SCC L1 Product correspond to a single emission
wavelength. For example it is possible to find in the same file the
elastic and the Raman channel pre-processed time-series corresponding to
the same emission wavelength (but to a different detection wavelengths)
but not two elastic time-series referring to different emission
wavelengths.

Low Resolution SCC L1 Product Format: dimensions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

The following dimensions are defined in the Low Resolution SCC L1
Product:

-  time
-  points
-  channels
-  scan\_angles

The dimension *time* specifies the number of RCS (for each channel)
composing all the pre-processed time-series reported in the file.

The dimension *points* represents the number of rangebins characterizing
the pre-processed RCS. In case RCSs corresponding to different channels
are characterized by different rangebins the dimension time is to the
the maximum value of rangebins.

The dimension *channels* indicates the number channels at which the RCS
time-series included in the file refer to.

The dimension *scan\_angles* takes into account how many zenith scan
angles have been used to measure the RCS time-series reported into the
file


Low Resolution SCC L1 Product Format: variables
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In this section all the possible Low Resolution SCC L1 Product variables
are reported. There are some variables that are mandatory and have to be
present in all the Low Resolution SCC L1 Product files while there are
others that have to be present only in specific cases.

Technical Variables
###################

altitude\_resolution
    :Type: *double*
    :Dimensions: *scan\_angles*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double altitude_resolution(scan_angles)``

    This variable describes the altitude resolution
    corresponding to the RCS time-series reported in the file. It is needed
    to compute the vertical scale of the RCS corresponding to each scan
    angle which should be calculated as it follow:
        
    .. math::

        H(\alpha, z)= \Delta h(\alpha)\left(z + \frac{1}{2}\right)
            
    where *z* is the altitude, :math:`\alpha` is the scan angle value and :math:`\Delta h` is the
    value reported by *altitude\_resolution* variable.

range\_resolution
    :Type: *double*
    :Dimensions: *scan\_angles*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double range_resolution(scan_angles)``

    This variable describes the range resolution corresponding
    to the RCS time-series reported in the file. It is needed to compute the
    range scale of the RCS corresponding to each scan angle which should be
    calculated as it follow:

    .. math::

            R(\alpha, z)= \Delta r(\alpha)\left(r + \frac{1}{2}\right)
            
    where *r* is the range, :math:`\alpha` is the scan angle value and :math:`\Delta r` is the
    value reported by *range\_resolution* variable. Altitude and range
    resolution are the same if the scan angle is zero (zenith acquisition).

laser\_pointing\_angle
    :Type: *double*
    :Dimensions: *scan\_angles*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double laser_pointing_angle(scan_angles)``

    This variable provides the value of the zenith scan angles
    used during the measurement. The value of angle are in degrees with
    respect to the zenith direction.

emission\_wavelength
    :Type: *double*
    :Dimensions: *channels*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double emission_wavelength(channels)``

    This variable provides the value of the emission wavelength
    (in nm) corresponding to each RCS time-series.

detection\_wavelength
    :Type: *double*
    :Dimensions: *channels*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double detection_wavelength(channels)``

    This variable provides the value of the detection
    wavelength (in nm) corresponding to each RCS time-series. For elastic
    channels the detection and emission wavelength are the same or slightly
    different.

laser\_pointing\_angle\_of\_profiles
    :Type: *integer*
    :Dimensions: *time*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``int laser_pointing_angle_of_profiles(time)``

    This variable allows to identify the zenith angle at which
    each single RCS contained in the time-series refer to. In particular,
    for a given time the variable
    *laser\_pointing\_angle\_of\_profiles(time)* provides the scan angle
    index at which all the RCS included in the file refer to at the same
    time. To get the value of the scan angle the variable
    *laser\_pointing\_angle* should be evaluated in correspondence of the
    index returned by the variable
    *laser\_pointing\_angle\_of\_profiles(time)*.

shots
    :Type: *integer*
    :Dimensions: *time*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``int shots(time)``

    This variable report the number of laser shots that have
    been integrated the all the RCS time-series at a given time.

start\_time
    :Type: *integer*
    :Dimensions: *time*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``int start_time(time)``

    Variable reporting the value of the start time of each RCS
    within all the time-series in seconds since the start of measurement.

stop\_time
    :Type: *integer*
    :Dimensions: *time*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``int stop_time(time)``

    Variables reporting the value of the stop time of each RCS
    within all the time-series in seconds since the start of the
    measurement.

LR\_Input
    :Type: *integer*
    :Dimensions: N/A
    :Location: Present only if the Low Resolution SCC L1 Product corresponds
               to an elastic only product
    :Definition: ``int LR_Input``

    This variable is only used by ELDA module in the elastic
    only retrieval to know which value of particle lidar ratio assume in the
    retrieval. A value of 1 means to use a fixed value stored in the SCC
    database for each product. A value of 0 means to use a profile of lidar
    ratio provided by the user as external file.

overlap\_correction
    :Type: *integer*
    :Dimensions: N/A
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``int overlap_correction``

    This variable provides information on the overlap
    correction of all the RCS time-series included in the file. If it is set
    to 1 the overlap correction has been applied if it is set to null value
    the overlap correction has not been applied.

cloud\_flag
    :Type: *integer*
    :Dimensions: *time, points*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``int cloud_flag(time, points)``

    variable reporting the cloud mask on the RCS time-series
    included in the file. A value of 1 means no cloud any other values
    different from 1 correspond to the presence of cloud.

Atmospheric Molecular Variables
###############################

Elastic\_Mol\_Extinction
    :Type: *double*
    :Dimensions: *scan\_angles, points*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: *double Elastic\_Mol\_Extinction(scan\_angles, points)*

    This variable provides the value of molecular extinction
    coefficient at elastic wavelength in m\ :sup:`-1` at a given scan angle
    and altitude (points). The values are calculated from standard models or
    from radiosounding (submitted to the SCC as external input files)

LR\_Mol
    :Type: *double*
    :Dimensions: N/A
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double LR_Mol``

    The value of calculated molecular lidar ratio in sr.

Emission\_Wave\_Mol\_Trasmissivity
    :Type: *double*
    :Dimensions: *scan\_angles, points*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double Emission_Wave_Mol_Trasmissivity(scan_angles, points)``

    This variable provides the value of molecular trasmissitivy
    at emission wavelength at a given scan angle and altitude (*points*).

Detection\_Wave\_Mol\_Trasmissivity
    :Type: *double*
    :Dimensions: *scan\_angles, points*
    :Location: Included in all the Low Resolution SCC L1 Product files
    :Definition: ``double Detection_Wave_Mol_Trasmissivity(scan_angles, points)``

    This variable provides the value of molecular trasmissitivy
    at detection wavelength at a given scan angle and altitude (*points*).

Aerosol Related Variables
#########################

elT
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves one
               single elastic channel not split in near and far range
    :Definition: ``double elT(time, points)``

    This variable contains the time-series of the RCS
    corresponding to an elastic channel. The RCS may correspond to a single
    physical lidar channel or to two physical channels (one optimized for
    the near range and the other for the far range) that have been glued by
    ELPP module.

elT\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves one
               single elastic channel not split in near and far range
    :Definition: ``double elT_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elT*.

elTnr
    :Variable name: *elTnr*
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a near
               range elastic channel
    :Definition: ``double elTnr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to a near range elastic channel. If this variable is
    present also the corresponding *elTfr* variable should be present in
    the file.

elTnr\_err
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a near
               range elastic channel
    :Definition: ``double elTnr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elTnr*.

elTfr
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a far
               range elastic channel
    :Definition: ``double elTfr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to a far range elastic channel. If this variable is
    present also the corresponding *elTnr* variable should be present in
    the file.

elTfr\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a far
               range elastic channel
    :Definition: ``double elTfr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elTfr*.

vrRN2
    :Type: * double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves one
               vibro-rotational N2 Raman channel not split in near and far range
    :Definition: ``double vrRN2(time, points)``

    This variable contains the time-series of the RCS
    corresponding to a vibro-rotational N2 Raman channel. The RCS may
    correspond to a single physical lidar channel or to two physical
    channels (one optimized for the near range and the other for the far
    range) that have been glued by ELPP module.

vrRN2\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves one
               vibro-rotational N2 Raman channel not split in near and far range
    :Definition: ``double vrRN2_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *vrRN2*.

vrRN2nr
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a near
               range vibro-rotational N2 Raman channel
    :Definition: ``double vrRN2nr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to a near range vibro-rotationl N2 Raman. If this variable
    is present also the corresponding *vrRN2fr* variable should be present
    in the file.

vrRN2nr\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a near
               range vibro-rotational N2 Raman channel
    :Definition: ``double vrRN2nr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *vrRN2nr*.

vrRN2fr
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a far
               range vibro-rotational N2 Raman channel
    :Definition: ``double vrRN2fr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to a far range vibro-rotationl N2 Raman. If this variable
    is present also the corresponding *vrRN2nr* variable should be present
    in the file.

vrRN2fr\_err
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves a far
               range vibro-rotational N2 Raman channel
    :Definition: ``double vrRN2fr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *vrRN2fr*.

Polarization related variables
##############################

elPT
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels not split in near and far range
    :Definition: ``double elPT(time, points)``

    This variable contains the time-series of the RCS
    corresponding to the elastic polarization component which is transmitted
    by the polarization sensitive optical subsystem. This component may
    correspond to a total, cross or parallel polarization component
    depending on the particular system configuration. Moreover the RCS may
    correspond to a single physical lidar channel or to two physical
    channels (one optimized for the near range and the other for the far
    range) that have been glued by ELPP module.

elPT\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves
               spolarization sensitive elastic channels not split in near and far range
    :Definition: ``double elPT_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elPT*.

elPTnr
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double elPTnr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to the near range elastic polarization component which is
    transmitted by the polarization sensitive optical subsystem. This
    component may correspond to a total, cross or parallel polarization
    component depending on the particular system configuration. If this
    variable is present also the corresponding *elPTfr* variable should be
    present in the file.

elPTnr\_err
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double elPTnr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elPTnr*.

elPTfr
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double elTfr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to the far range elastic polarization component which is
    transmitted by the polarization sensitive optical subsystem. This
    component may correspond to a total, cross or parallel polarization
    component depending on the particular system configuration. If this
    variable is present also the corresponding elPTnr variable should be
    present in the file.

elPTfr\_err
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double elPTfr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elPTfr*.

elPR
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels not split in near and far range
    :Definition: ``double elPR(time, points)``

    This variable contains the time-series of the RCS
    corresponding to the elastic polarization component which is reflected
    by the polarization sensitive optical subsystem. This component may
    correspond to a total, cross or parallel polarization component
    depending on the particular system configuration. Moreover the RCS may
    correspond to a single physical lidar channel or to two physical
    channels (one optimized for the near range and the other for the far
    range) that have been glued by ELPP module.

elPR\_err
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels not split in near and far range
    :Definition: ``double elPR_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elPR*.

elPRnr
    :Type: *double*
    :Dimensions: * time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double elPTnr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to the near range elastic polarization component which is
    reflected by the polarization sensitive optical subsystem. This
    component may correspond to a total, cross or parallel polarization
    component depending on the particular system configuration. If this
    variable is present also the corresponding *elPRfr* variable should be
    present in the file.

elPRnr\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: `` double elPRnr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elPRnr*.

elPRfr
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double elPRfr(time, points)``

    This variable contains the time-series of the RCS
    corresponding to the far range elastic polarization component which is
    reflected by the polarization sensitive optical subsystem. This
    component may correspond to a total, cross or parallel polarization
    component depending on the particular system configuration. If this
    variable is present also the corresponding *elPRnr* variable should be
    present in the file.

elPRfr\_err
    :Type: *double*
    :Dimensions: *time, points*
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double elPRfr_err(time, points)``

    This variable describes the statistical uncertainties
    corresponding to the variable *elPRfr*.

G\_T
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double G_T``

    G polarization cross-talk factor value corresponding to the
    polarization transmitted channel.

G\_T\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double G_T_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *G\_T*.

G\_T\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double G_T_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *G\_T*.

H\_T
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double H_T``

    H polarization cross-talk factor value corresponding to the
    polarization transmitted channel.

H\_T\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double H_T_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *H\_T*.

H\_T\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double H_T_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *H\_T*.

G\_R
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double G_R``

    G polarization cross-talk factor value corresponding to the
    polarization reflected channel.

G\_R\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double G_R_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *G\_R*.

G\_R\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: `` double G_R_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *G\_R*.

H\_R
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double H_R``

    H polarization cross-talk factor value corresponding to the
    polarization reflected channel.

H\_R\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double H_R_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *H\_R*.

H\_R\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double H_R_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *H\_R*.

Polarization\_Channel\_Gain\_Factor
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor``

    This variable reports the value of the gain ratio of the
    reflected and transmitted polarization channels.

Polarization\_Channel\_Gain\_Factor\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor*.

Polarization\_Channel\_Gain\_Factor\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor*.

Polarization\_Channel\_Gain\_Factor\_Correction
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction``

    This variable reports the value of the correction to the
    gain ratio of the reflected and transmitted polarization channels.

Polarization\_Channel\_Gain\_Factor\_Correction\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable

Polarization\_Channel\_Gain\_Factor\_Correction

Polarization\_Channel\_Gain\_Factor\_Correction\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor\_Correction*.

G\_T\_Near\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double G_T_Near_Range``

    G polarization cross-talk factor value corresponding to the
    near range polarization transmitted channel.

G\_T\_Near\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double G_T_Near_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *G\_T\_Near\_Range*.

G\_T\_Near\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double G_T_Near_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *G\_T\_Near\_Range*.

H\_T\_Near\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double H_T_Near_Range``

    H polarization cross-talk factor value corresponding to the
    near range polarization transmitted channel.

H\_T\_Near\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double H_T_Near_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *H\_T\_Near\_Range*.

H\_T\_Near\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double H_T_Near_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *H\_T\_Near\_Range*.

G\_R\_Near\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double G_R_Near_Range``

    G polarization cross-talk factor value corresponding to the
    near range polarization reflected channel.

G\_R\_Near\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double G_R_Near_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *G\_R\_Near\_Range*.

G\_R\_Near\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double G_R_Near_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *G\_R\_Near\_Range*.

H\_R\_Near\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double H_R_Near_Range``

    H polarization cross-talk factor value corresponding to the
    near range polarization reflected channel.

H\_R\_Near\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double H_R_Near_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *H\_R\_Near\_Range*.

H\_R\_Near\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double H_R_Near_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *H\_R\_Near\_Range*.

Polarization\_Channel\_Gain\_Factor\_Near\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Near_Range``

    This variable reports the value of the gain ratio of the
    near range reflected and transmitted polarization channels.

Polarization\_Channel\_Gain\_Factor\_Near\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Near_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Near\_Range\_Factor*.

Polarization\_Channel\_Gain\_Factor\_Near\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Near_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor\_Near\_Range*.

Polarization\_Channel\_Gain\_Factor\_Correction\_Near\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Near_Range``

    This variable reports the value of the correction to the
    near range gain ratio of the reflected and transmitted polarization
    channels.

Polarization\_Channel\_Gain\_Factor\_Correction\_Near\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Near_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable Polarization\_Channel\_Gain\_Factor\_Correction\_Near\_Range
    
Polarization\_Channel\_Gain\_Factor\_Correction\_Near\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves near
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Near_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor\_Correction\_Near\_Range*.

G\_T\_Far\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double G_T_Far_Range``

    G polarization cross-talk factor value corresponding to the
    far range polarization transmitted channel.

G\_T\_Far\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double G_T_Far_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *G\_T\_Far\_Range*.

G\_T\_Far\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double G_T_Far_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *G\_T\_Far\_Range*.

H\_T\_Far\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double H_T_Far_Range``

    H polarization cross-talk factor value corresponding to the
    far range polarization transmitted channel.

H\_T\_Far\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double H_T_Far_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *H\_T\_Far\_Range*.

H\_T\_Far\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double H_T_Far_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *H\_T\_Far\_Range*.

G\_R\_Far\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double G_R_Far_Range``

    G polarization cross-talk factor value corresponding to the
    far range polarization reflected channel.

G\_R\_Far\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double G_R_Far_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *G\_R\_Far\_Range*.

G\_R\_Far\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double G_R_Far_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *G\_R\_Far\_Range*.

H\_R\_Far\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double H_R_Far_Range``

    H polarization cross-talk factor value corresponding to the
    far range polarization reflected channel.

H\_R\_Far\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double H_R_Far_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *H\_R\_Far\_Range*.

H\_R\_Far\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double H_R_Far_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *H\_R\_Far\_Range*.

Polarization\_Channel\_Gain\_Factor\_Far\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Far_Range``

    This variable reports the value of the gain ratio of the
    far range reflected and transmitted polarization channels.

Polarization\_Channel\_Gain\_Factor\_Far\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Far_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable
    *Polarization\_Channel\_Gain\_Far\_Range\_Factor*.

Polarization\_Channel\_Gain\_Factor\_Far\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Far_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor\_Far\_Range*.

Polarization\_Channel\_Gain\_Factor\_Correction\_Far\_Range
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Far_Range``

    This variable reports the value of the correction to the
    far range gain ratio of the reflected and transmitted polarization
    channels.
    
Polarization\_Channel\_Gain\_Factor\_Correction\_Far\_Range\_Statistical\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Far_Range_Statistical_Err``

    This variable describes the statistical uncertainties
    corresponding to the variable *Polarization\_Channel\_Gain\_Factor\_Correction\_Far\_Range*.

Polarization\_Channel\_Gain\_Factor\_Correction\_Far\_Range\_Systematic\_Err
    :Type: *double*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves far
               range polarization sensitive elastic channels
    :Definition: ``double Polarization_Channel_Gain_Factor_Correction_Far_Range_Systematic_Err``

    This variable describes the systematic uncertainties
    corresponding to the variable
    *Polarization\_Channel\_Gain\_Factor\_Correction\_Far\_Range*.

Depolarization\_Calibration\_Type
    :Type: *integer*
    :Dimensions: N/A
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``int Depolarization_Calibration_Type``

    This variable describes the type of depolarization
    calibration that has been performed. A value of 1 means automatic
    calibration made the the SCC, a value of 2 means manual calibration
    inserted into the SCC database.

Molecular\_Linear\_Depolarization\_Ratio
    :Type: *double*
    :Dimensions: *scan\_angles,points*
    :Location: Present if the Low Resolution SCC L1 Product involves
               polarization sensitive elastic channels
    :Definition: ``double Molecular_Linear_Depolarization_Ratio(scan_angles, points)``

    This variable report the value of molecular linear
    depolarization ration for at given scan angles and at given altitude
    (*points*). This profile is calculated on the base of the atmospheric
    data from standard models or radiosonding submitted by the user as
    separate file.

The altitude scale at which each RCS within the time-series reported by
the variables *elT, elTnr, elTfr, vrRN2, vrRN2nr, vrRN2fr, elPT, elPTnr,
elPTfr, elPR, elPRnr, elPRfr*, refer to can be obtained as::

    H(laser_pointing_angle_of_profiles(time),points)

The total signal (:math:`I_{total}`) and the volume depolarization
ratio (:math:`\delta`) can be calculated out of reflected (:math:`I_{R}`) and
transmitted (:math:`I_{T}`) polarization component intensities using
the following equations:

.. math::

   \delta^{*} = \frac{K}{\eta^{*}}\frac{I_R}{I_T}

.. math::

   \delta = \frac{\delta^{*} (G_T + H_T) - (G_R + H_R)}{(G_R - H_R) - \delta_{*}(G_T - H_T)}

.. math::

   I_{total} \propto \frac{\eta^{*}}{K} H_R I_T - H_T I_R

where :math:`\eta^{*}` is the gain ratio of the reflected and transmitted
polarization channels (variable *Polarization\_Channel\_Gain\_Factor*);
:math:`K` is the correction to the gain ratio of the reflected and transmitted
polarization channels (variable *Polarization\_Channel\_Gain\_Factor\_Correction*);
:math:`I_{R}` is the intensity of the reflected polarization component (variable *elPR*);
:math:`I_{T}` is the intensity of the transmitted polarization
component (variable *elPT*); and :math:`G_{T}`, :math:`H_{T}`,
:math:`G_{R}`, and :math:`H_{R}` are the polarization cross-talk
parameters (variables *G\_T*, *H\_T*, *G\_R*, and *H\_R*).

Low Resolution SCC L1 Product Format: global attributes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

In this section all the possible Low Resolution SCC L1 Product global
attributes are reported. There are some global attributes that are
mandatory and have to be present in all the Low Resolution SCC L1
Product files while there are others that have to be present only in
specific cases.

Location
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The name of site where the measurements have been performed

System
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The name of the lidar system used to perform the
    measurements

Latitude\_degrees\_north
    :Type: *double*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The latitude (in degrees North) of the measurement site

Longitude\_degrees\_east
    :Type: *double*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The longitude (in degrees East) of the measurement site

Altitude\_meter\_asl
    :Type: *double*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The altitude (in m above see level) of the measurement site

Measurement\_ID
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    Within the SCC all the measurement sessions is identified
    by a string called *Measurement\_ID* uniquely. This gobal attributes
    provides this string.

Measurement\_Start\_Date
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The start date of the measurements. The format in which
    this date is written is specified in the gobal attribute
    *Measurement\_Date\_Format*.

Measurement\_Date\_Format
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The format in which the global attribute
    *Measurement\_Start\_Date* is given.

Measurement\_Start\_Time\_UT
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The start time (UT) of the measurements. The format in
    which this time is written is specified in the global attribute
    *Measurement\_Time\_Format*.

Measurement\_Time\_Format
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The format in which the global attribute
    *Measurement\_Start\_Time\_U*\ T is given.

Comments
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    This string can contain comments of the measurement session

Overlap\_File\_Name
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files for
               which an overlap file has been submitted by the data originator.

    The name of the overlap file to use for overlap correction.

LR\_File\_Name
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files
               corresponding to elastic only retrieval and for which an lidar ratio
               profile file has been submitted by the data originator.

    The name of the lidar ratio file containing the profile of
    particle lidar ratio values to use as input in the elastic only
    retrieval.

SCCPreprocessingVersion
    :Type: *string*
    :Location: Included in all the Low Resolution SCC L1 Product files

    The version of SCC used to produce the current Low
    Resolution SCC L1 Product

Low Resolution SCC L1 Product Filename
--------------------------------------

The filename of the Low Resolution SCC L1 Products has the following
format::

    measurementid_prodid.nc

The *measurementid* is a 12 characters alphanumeric string identifying
the measurement session at which the product refers to. The
*measurementid* (which is unique for a given measurement session) allows
to fully trance the SCC analysis performed on the current product. This
can be done because each measurement session is recorded in a SCC
database using the same string. In the same database the measurement
session is linked to the lidar configuration used to analyze the data
(which is recorded and fully characterized in the SCC database providing
all the channel details) and to a set of optical products to calculate.

The *prodid* is a numeric string identifying the optical product that
has to be calculated by SCC (in particular ELDA module) by applying the
optical retrieval algorithm on the current pre-processed L1 product.

Different product types are defined within the SCC. The contents of a
Low Resolution SCC L1 product depends on the type of the product
specified in the its filename by prodid string. In particular only the
**Aerosol Related Variables **\ and\ ** Polarization related variables**
specified in the section 2.2 can change depending on product type. In
Tab. 3.1 are reported the product-type related variables for each
optical product type.

To link the *prodid* string with the corresponding product type the SCC
database a proper query to the SCC database should be addressed.

**Table 3.1:** Possible variables that can be found in the SCC L1
Products for each optical product type

+--------------------------------------------------------------+---------------------------------------------------+
| Product type                                                 | Possible variables in Low Resolution L1 Product   |
+--------------------------------------------------------------+---------------------------------------------------+
| Extinction only                                              | vrRN2, vrRN2nr, vrRN2fr                           |
|                                                              |                                                   |
|                                                              | vrRN2\_err, vrRN2nr\_err, vrRN2fr\_err            |
+--------------------------------------------------------------+---------------------------------------------------+
| Elastic Backscatter                                          | elT, elTnr, elTfr                                 |
|                                                              |                                                   |
| Elastic Backscatter + Particle Linear Depolarization Ratio   | elT\_err, elTnr\_err, elTfr\_err                  |
|                                                              |                                                   |
|                                                              | elPR, elPRnr, elPRfr                              |
|                                                              |                                                   |
|                                                              | elPR\_err, elPRnr\_err, elPRfr\_err               |
|                                                              |                                                   |
|                                                              | elPT, elPTnr, elPTfr                              |
|                                                              |                                                   |
|                                                              | elPT\_err, elPTnr\_err, elPTfr\_err               |
+--------------------------------------------------------------+---------------------------------------------------+
| Raman Backscatter                                            | elT, elTnr, elTfr                                 |
|                                                              |                                                   |
| Raman Backscatter + Particle Linear Depolarization Ratio     | elT\_err, elTnr\_err, elTfr\_err                  |
|                                                              |                                                   |
| Lidar Ratio                                                  | elPR, elPRnr, elPRfr                              |
|                                                              |                                                   |
|                                                              | elPR\_err, elPRnr\_err, elPRfr\_err               |
|                                                              |                                                   |
|                                                              | elPT, elPTnr, elPTfr                              |
|                                                              |                                                   |
|                                                              | elPT\_err, elPTnr\_err, elPTfr\_err               |
|                                                              |                                                   |
|                                                              | vrRN2, vrRN2nr, vrRN2fr                           |
|                                                              |                                                   |
|                                                              | vrRN2\_err, vrRN2nr\_err, vrRN2fr\_err            |
+--------------------------------------------------------------+---------------------------------------------------+
