--- a/netcdf_file.rst Fri May 11 13:22:25 2012 +0200
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,1187 +0,0 @@
-The SCC netCDF file format
-==========================
-
-Rationale
----------
-
-The Single Calculus Chain (SCC) is composed by two different modules:
-
-- pre-processing module ( scc\_preprocessing)
-
-- optical processing module ( ELDA)
-
-To perfom aerosol optical retrievals the SCC needs not only the raw
-lidar data but also a certain number of parameters to use in both
-pre-processing and optical processing stages. The SCC gets these
-parameters looking at two different locations:
-
-- Single Calculus Chain relational database (SCC\_DB)
-
-- Input files
-
-There are some paramenters that can be found only in the input files
-(those ones changing from measurement to measurement), others that can
-be found only in the SCC\_DB and other ones that can be found in both
-these locations. In the last case, if a particular parameter is needed,
-the SCC will search first in the input files and then in SCC\_DB. If the
-parameter is found in the input files the SCC will keep it without
-looking into SCC\_DB.
-
-The input files have to be submitted to the SCC in NetCDF format. At the
-present the SCC can handle four different types of input files:
-
-1. Raw Lidar Data
-2. Sounding Data
-3. Overlap
-4. Lidar Ratio
-
-
-As already mentioned, the Raw Lidar Data file contains not only the
-raw lidar data but also other parameters to use to perform the
-pre-processing and optical processing. The Sounding Data file
-contains the data coming from a correlative radiosounding and it is used
-by the SCC for molecular density calculation. The Overlap file
-contains the measured overlap function. The Lidar Ratio file contains
-a lidar ratio profile to use in elastic backscatter retrievals. The
-Raw Lidar Data file is of course mandatory and the Sounding Data,
-Overlap and Lidar Ratio files are optional. If Sounding Data file
-is not submitted by the user, the molecular density will be calculated
-by the SCC using the “US Standard Atmosphere 1976”. If the Overlap
-file is not submitted by the user, the SCC will get the full overlap
-height from SCC\_DB and it will produce optical results starting from
-this height. If Lidar Ratio file is not submitted by the user, the
-SCC will consider a fixed value for lidar ratio got from SCC\_DB.
-
-The user can decide to submit all these files or any number of them (of
-course the file Raw Lidar Data is mandatory). For example the user
-can submit together with the Raw Lidar Data file only the Sounding
-Data file or only the Overlap file.
-
-This document provides a detailed explanation about the structure of the
-NetCDF input files to use for SCC data submission. All Earlinet groups
-should read it carefully because they have to produce such kind of input
-files if they want to use the SCC for their standard lidar retrievals.
-Every comments or suggestions regarding this document can be sent to
-Giuseppe D’Amico by e-mail at ``damico@imaa.cnr.it``
-
-This document is available for downloading at ``www.earlinetasos.org``
-
-In table tab:rawdata is reported a list of dimensions, variables and
-global attributes that can be used in the NetCDF Raw Lidar Data input
-file. For each of them it is indicated:
-
-- The name. For the multidimensional variables also the corresponding
- dimensions are reported
-
-- A description explaining the meaning
-
-- The type
-
-- If it is mandatory or optional
-
-As already mentioned, the SCC can get some parameters looking first in
-the Raw Lidar Data input file and then into SCC\_DB. This means that
-to use the parameters stored in SCC\_DB the optional variables or
-optional global attributes must not appear within Raw Lidar Data
-file. This is the suggested and recommended way to use the SCC. Please
-include optional parameters in the Raw Lidar Data only as an
-exception.
-
-In table tab:sounding, tab:overlap and tab:lr are reported all the
-information about the structure of Sounding Data, Overlap and
-Lidar Ratio input files respectively.
-
-Example
--------
-
-Let’s now consider an example of Raw Lidar Data input file. Suppose
-we want to generate NetCDF input file corresponding to a measurement
-with the following properties:
-
-+----------------------+-------------------------------------------+
-| Start Date | :math:`30^{th}` January 2009 |
-+----------------------+-------------------------------------------+
-| Start Time UT | 00:00:01 |
-+----------------------+-------------------------------------------+
-| Stop Time UT | 00:05:01 |
-+----------------------+-------------------------------------------+
-| Station Name | Dummy station |
-+----------------------+-------------------------------------------+
-| Earlinet call-sign | cc |
-+----------------------+-------------------------------------------+
-| Pointing angle | 5 degrees with respect to the zenith |
-+----------------------+-------------------------------------------+
-
-Moreover suppose that this measurement is composed by the following
-lidar channels:
-
-1. 1064 lidar channel
-
- +------------------------------+-------------------------------+
- | Emission wavelength=1064nm | Detection wavelength=1064nm |
- +------------------------------+-------------------------------+
- | Time resolution=30s | Number of laser shots=1500 |
- +------------------------------+-------------------------------+
- | Number of bins=3000 | Detection mode=analog |
- +------------------------------+-------------------------------+
- | Range resolution=7.5m | Polarization state=total |
- +------------------------------+-------------------------------+
-
-2. 532 cross lidar channel
-
- +-----------------------------+---------------------------------+
- | Emission wavelength=532nm | Detection wavelength=532nm |
- +-----------------------------+---------------------------------+
- | Time resolution=60s | Number of laser shots=3000 |
- +-----------------------------+---------------------------------+
- | Number of bins=5000 | Detection mode=photoncounting |
- +-----------------------------+---------------------------------+
- | Range resolution=15m | Polarization state=cross |
- +-----------------------------+---------------------------------+
-
-3. 532 parallel lidar channel
-
- +-----------------------------+---------------------------------+
- | Emission wavelength=532nm | Detection wavelength=532nm |
- +-----------------------------+---------------------------------+
- | Time resolution=60s | Number of laser shots=3000 |
- +-----------------------------+---------------------------------+
- | Number of bins=5000 | Detection mode=photoncounting |
- +-----------------------------+---------------------------------+
- | Range resolution=15m | Polarization state=parallel |
- +-----------------------------+---------------------------------+
-
-4. 607 :math:`N_2` vibrational Raman channel
-
- +-----------------------------+---------------------------------+
- | Emission wavelength=532nm | Detection wavelength=607nm |
- +-----------------------------+---------------------------------+
- | Time resolution=60s | Number of laser shots=3000 |
- +-----------------------------+---------------------------------+
- | Number of bins=5000 | Detection mode=photoncounting |
- +-----------------------------+---------------------------------+
- | Range resolution=15m |
- +-----------------------------+---------------------------------+
-
-Finally let’s assume we have also performed dark measurements before the
-lidar measurements from the 23:50:01 UT up to 23:53:01 UT of
-29:math:`^\mathrmth` January 2009.
-
-Dimensions
-~~~~~~~~~~
-
-Looking at table tab:rawdata we have to fix the following dimensions:
-
-::
-
- points
- channels
- time
- nb_of_time_scales
- scan_angles
- time_bck
-
-The dimension ``time`` is unlimited so we don’t have to fix it.
-
-We have 4 lidar channels so:
-
-::
-
- channels=4
-
-Regarding the dimension ``points`` we have only one channel with a
-number of vertical bins equal to 3000 (the 1064nm) and all other
-channels with 5000 vertical bins. In cases like this the dimension
-``points`` has to be fixed to the maximum number of vertical bins so:
-
-::
-
- points=5000
-
-Moreover only one channel (1064nm) is acquired with a time resolution of
-30 seconds, all the other channels have a time resolution of 60 seconds.
-This means that we have to define two different time scales. We have to
-set:
-
-::
-
- nb_of_time_scales=2
-
-The measurement is performed only at one scan angle (5 degrees with
-respect to the zenith) so:
-
-::
-
- scan_angles=1
-
-We have 3 minutes of dark measurements and two different time scales one
-with 60 seconds time resolution and the other one with 30 seconds time
-resolution. So we will have 3 different dark profiles for the channels
-acquired with the first time scale and 6 for the lidar channels acquired
-with the second time scale. We have to fix the dimension ``time_bck`` as
-the maximum between these values:
-
-::
-
- time_bck=6
-
-Variables
-~~~~~~~~~
-
-In this section it will be explained how to fill all the possible
-variables either mandatory or optional of Raw Lidar Data input file.
-
-Raw_Data_Start_Time(time, nb_of_time_scales)
- This 2 dimensional mandatory array has to contain the acquisition
- start time (in seconds from the time given by the global attribute
- ``RawData_Start_Time_UT``) of each lidar profile. In this example we
- have two different time scales: one is characterized by steps of 30
- seconds (the 1064nm is acquired with this time scale) the other by
- steps of 60 seconds (532cross, 532parallel and 607nm). Moreover the
- measurement start time is 00:00:01 UT and the measurement stop time
- is 00:05:01 UT. In this case we have to define:
-
- ::
-
- Raw_Data_Start_Time =
- 0, 0,
- 60, 30,
- 120, 60,
- 180, 90,
- 240, 120,
- _, 150,
- _, 180,
- _, 210,
- _, 240,
- _, 270 ;
-
- The order used to fill this array defines the correspondence between
- the different time scales and the time scale index. In this example
- we have a time scale index of 0 for the time scale with steps of 60
- seconds and a time scale index of 1 for the other one.
-
-Raw_Data_Stop_Time(time, nb_of_time_scales)
- The same as previous item but for the data acquisition stop time.
- Following a similar procedure we have to define:
-
- ::
-
- Raw_Data_Stop_Time =
- 60, 30,
- 120, 60,
- 180, 90,
- 240, 120,
- 300, 150,
- _, 180,
- _, 210,
- _, 240,
- _, 270,
- _, 300 ;
-
-Raw_Lidar_Data(time, channels, points)
- This 3 dimensional mandatory array has to be filled with the
- time-series of raw lidar data. The photoncounting profiles have to
- submitted in counts (so as integers) while the analog ones in mV. The
- order the user chooses to fill this array defines the correspondence
- between channel index and lidar data.
-
- For example if we fill this array in such way that:
-
- +-------------------------------------+------------------------------------------------------------+
- | Raw_Lidar_Data(time,0,points | :math:`\rightarrow` is the time-series of 1064 nm |
- +-------------------------------------+------------------------------------------------------------+
- | Raw_Lidar_Data(time,1,points | :math:`\rightarrow` is the time-series of 532 cross |
- +-------------------------------------+------------------------------------------------------------+
- | Raw_Lidar_Data(time,2,points | :math:`\rightarrow` is the time-series of 532 parallel |
- +-------------------------------------+------------------------------------------------------------+
- | Raw_Lidar_Data(time,3,points | :math:`\rightarrow` is the time-series of 607 nm |
- +-------------------------------------+------------------------------------------------------------+
-
- from now on the channel index 0 is associated to the 1064 channel,
- 1 to the 532 cross, 2 to the 532 parallel and 3 to the 607nm.
-
-Raw_Bck_Start_Time(time_bck, nb_of_time_scales)
- This 2 dimensional optional array has to contain the acquisition
- start time (in seconds from the time given by the global attribute
- ``RawBck_Start_Time_UT``) of each dark measurements profile.
- Following the same procedure used for the variable
- ``Raw_Data_Start_Time`` we have to define:
-
- ::
-
- Raw_Bck_Start_Time =
- 0, 0,
- 60, 30,
- 120, 60,
- _, 90,
- _, 120,
- _, 150;
-
-Raw_Bck_Stop_Time(time_bck, nb_of_time_scales)
- The same as previous item but for the dark acquisition stop time.
- Following a similar procedure we have to define:
-
- ::
-
- Raw_Bck_Stop_Time =
- 60, 30,
- 120, 60,
- 180, 90,
- _, 120,
- _, 150,
- _, 180 ;
-
-
-Background_Profile(time_bck, channels, points)
- This 3 dimensional optional array has to be filled with the
- time-series of the dark measurements data. The photoncounting
- profiles have to submitted in counts (so as integers) while the
- analog ones in mV. The user has to fill this array following the same
- order used in filling the array ``Raw_Lidar_Data``:
-
- +---------------------------------------------+----------------------------------------------------------+
- | Background_Profile(time_bck,0,points | :math:`\rightarrow` dark time-series at 1064 nm |
- +---------------------------------------------+----------------------------------------------------------+
- | Background_Profile(time_bck,1,points | :math:`\rightarrow` dark time-series at 532 cross |
- +---------------------------------------------+----------------------------------------------------------+
- | Background_Profile(time_bck,2,points | :math:`\rightarrow` dark time-series at 532 parallel |
- +---------------------------------------------+----------------------------------------------------------+
- | Background_Profile(time_bck,3,points | :math:`\rightarrow` dark time-series at 607 nm |
- +---------------------------------------------+----------------------------------------------------------+
-
-
-channel_ID(channels)
- This mandatory array provides the link between the channel index
- within the Raw Lidar Data input file and the channel ID in
- SCC\_DB. To fill this variable the user has to know which channel IDs
- in SCC\_DB correspond to his lidar channels. For this purpose the
- SCC, in its final version will provide to the user a special tool to
- get these channel IDs through a Web interface. At the moment this
- interface is not yet available and these channel IDs will be
- communicated directly to the user by the NA5 people.
-
- Anyway to continue the example let’s suppose that the four lidar
- channels taken into account are mapped into SCC\_DB with the
- following channel IDs:
-
- +----------------+--------------------------------------+
- | 1064 nm | :math:`\rightarrow` channel ID=7 |
- +----------------+--------------------------------------+
- | 532 cross | :math:`\rightarrow` channel ID=5 |
- +----------------+--------------------------------------+
- | 532 parallel | :math:`\rightarrow` channel ID=6 |
- +----------------+--------------------------------------+
- | 607 nm | :math:`\rightarrow` channel ID=8 |
- +----------------+--------------------------------------+
-
- In this case we have to define:
-
- ::
-
- channel_ID = 7, 5, 6, 8 ;
-
-id_timescale(channels)
- This mandatory array is introduced to determine which time scale is
- used for the acquisition of each lidar channel. In particular this
- array defines the link between the channel index and the time scale
- index. In our example we have two different time scales. Filling the
- arrays ``Raw_Data_Start_Time`` and ``Raw_Data_Stop_Time`` we have
- defined a time scale index of 0 for the time scale with steps of 60
- seconds and a time scale index of 1 for the other one with steps of
- 30 seconds. In this way this array has to be set as:
-
- ::
-
- id_timescale = 1, 0, 0, 0 ;
-
-Laser_Pointing_Angle(scan_angles
- This mandatory array contains all the scan angles used in the
- measurement. In our example we have only one scan angle of 5 degrees
- with respect to the zenith, so we have to define:
-
- ::
-
- Laser_Pointing_Angle = 5 ;
-
-Laser_Pointing_Angle_of_Profiles(time, nb_of_time_scales)
- This mandatory array is introduced to determine which scan angle is
- used for the acquisition of each lidar profile. In particular this
- array defines the link between the time and time scales indexes and
- the scan angle index. In our example we have a single scan angle that
- has to correspond to the scan angle index 0. So this array has to be
- defined as:
-
- ::
-
- Laser_Pointing_Angle_of_Profiles =
- 0, 0,
- 0, 0,
- 0, 0,
- 0, 0,
- 0, 0,
- _, 0,
- _, 0,
- _, 0,
- _, 0,
- _, 0 ;
-
-Laser_Shots(time, channels)
- This mandatory array stores the laser shots accumulated at each time
- for each channel. In our example the number of laser shots
- accumulated is 1500 for the 1064nm channels and 3000 for all the
- other channels. Moreover the laser shots do not change with the time.
- So we have to define this array as:
-
- ::
-
- Laser_Shots =
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _ ;
-
-Emitted_Wavelength(channels)
- This optional array defines the link between the channel index and
- the emission wavelength for each lidar channel. The wavelength has to
- be expressed in nm. This information can be also taken from SCC\_DB.
- In our example we have:
-
- ::
-
- Emitted_Wavelength = 1064, 532, 532, 532 ;
-
-Detected_Wavelength(channels)
- This optional array defines the link between the channel index and
- the detected wavelength for each lidar channel. Here detected
- wavelength means the value of center of interferential filter
- expressed in nm. This information can be also taken from SCC\_DB. In
- our example we have:
-
- ::
-
- Detected_Wavelength = 1064, 532, 532, 607 ;
-
-Raw_Data_Range_Resolution(channels)
- This optional array defines the link between the channel index and
- the raw range resolution for each channel. If the scan angle is
- different from zero this quantity is different from the vertical
- resolution. More precisely if :math:`\alpha` is the scan angle used
- and :math:`\Delta z` is the range resolution the vertical
- resolution is calculated as :math:`\Delta
- z'=\Delta z \cos\alpha`. This array has to be filled with
- :math:`\Delta z` and not with :math:`\Delta z'`. The unit is
- meters. This information can be also taken from SCC\_DB. In our
- example we have:
-
- ::
-
- Raw_Data_Range_Resolution = 7.5, 15.0, 15.0, 15.0 ;
-
-ID_Range(channels)
- This optional array defines if a particular channel is configured as
- high, low or ultranear range channel. In particular a value 0
- indicates a low range channel, a value 1 a high range channel and a
- value of 2 an ultranear range channel. If for a particular channel
- you don’t separate between high and low range channel, please set the
- corresponding value to 1. This information can be also taken from
- SCC\_DB. In our case we have to set:
-
- ::
-
- ID_Range = 1, 1, 1, 1 ;
-
-Scattering_Mechanism(channels)
- This optional array defines the scattering mechanism involved in
- each lidar channel. In particular the following values are adopted:
-
- +------+---------------------------------------------------------------------------------------------+
- | 0 | :math:`\rightarrow` Total elastic backscatter |
- +------+---------------------------------------------------------------------------------------------+
- | 1 | :math:`\rightarrow` :math:`N_2` vibrational Raman backscatter |
- +------+---------------------------------------------------------------------------------------------+
- | 2 | :math:`\rightarrow` Cross polarization elastic backscatter |
- +------+---------------------------------------------------------------------------------------------+
- | 3 | :math:`\rightarrow` Parallel polarization elastic backscatter |
- +------+---------------------------------------------------------------------------------------------+
- | 4 | :math:`\rightarrow` :math:`H_2O` vibrational Raman backscatter |
- +------+---------------------------------------------------------------------------------------------+
- | 5 | :math:`\rightarrow` Rotational Raman Stokes line close to elastic line |
- +------+---------------------------------------------------------------------------------------------+
- | 6 | :math:`\rightarrow` Rotational Raman Stokes line far from elastic line |
- +------+---------------------------------------------------------------------------------------------+
- | 7 | :math:`\rightarrow` Rotational Raman anti-Stokes line close to elastic line |
- +------+---------------------------------------------------------------------------------------------+
- | 8 | :math:`\rightarrow` Rotational Raman anti-Stokes line far from elastic line |
- +------+---------------------------------------------------------------------------------------------+
- | 9 | :math:`\rightarrow` Rotational Raman Stokes and anti-Stokes lines close to elastic line |
- +------+---------------------------------------------------------------------------------------------+
- | 10 | :math:`\rightarrow` Rotational Raman Stokes and anti-Stokes lines far from elastic line |
- +------+---------------------------------------------------------------------------------------------+
-
- This information can be also taken from SCC\_DB. In our example we have:
-
- ::
-
- Scattering_Mechanism = 0, 2, 3, 1 ;
-
-Acquisition_Mode(channels)
- This optional array defines the acquisition mode (analog or
- photoncounting) involved in each lidar channel. In particular a value
- of 0 means analog mode and 1 photoncounting mode. This information
- can be also taken from SCC\_DB. In our example we have:
-
- ::
-
- Acquisition_Mode = 0, 1, 1, 1 ;
-
-Laser_Repetition_Rate(channels)
- This optional array defines the repetition rate in Hz used to
- acquire each lidar channel. This information can be also taken from
- SCC\_DB. In our example we are supposing we have only one laser with
- a repetition rate of 50 Hz so we have to set:
-
- ::
-
- Laser_Repetition_Rate = 50, 50, 50, 50 ;
-
-Dead_Time(channels)
- This optional array defines the dead time in ns associated to each
- lidar channel. The SCC will use the values given by this array to
- correct the photoncounting signals for dead time. Of course for
- analog signals no dead time correction will be applied (for analog
- channels the corresponding dead time values have to be set to
- undefined value). This information can be also taken from SCC\_DB. In
- our example the 1064 nm channel is acquired in analog mode so the
- corresponding dead time value has to be undefined. If we suppose a
- dead time of 10 ns for all other channels we have to set:
-
- ::
-
- Dead_Time = _, 10, 10, 10 ;
-
-Dead_Time_Corr_Type(channels
- This optional array defines which kind of dead time correction has
- to be applied on each photoncounting channel. The SCC will correct
- the data supposing a not-paralyzable channel if a value of 0 is found
- while a paralyzable channel is supposed if a value of 1 is found. Of
- course for analog signals no dead time correction will be applied and
- so the corresponding values have to be set to undefined value. This
- information can be also taken from SCC\_DB. In our example the 1064
- nm channel is acquired in analog mode so the corresponding has to be
- undefined. If we want to consider all the photoncounting signals as
- not-paralyzable ones: we have to set:
-
- ::
-
- Dead_Time_Corr_Type = _, 0, 0, 0 ;
-
-Trigger_Delay(channels)
- This optional array defines the delay (in ns) of the middle of the
- first rangebin with respect to the output laser pulse for each lidar
- channel. The SCC will use the values given by this array to correct
- for trigger delay. This information can be also taken from SCC\_DB.
- Let’s suppose that in our example all the photoncounting channels are
- not affected by this delay and only the analog channel at 1064nm is
- acquired with a delay of 50ns. In this case we have to set:
-
- ::
-
- Trigger_Delay = 50, 0, 0, 0 ;
-
-Background_Mode(channels
- This optional array defines how the atmospheric background has to be
- subtracted from the lidar channel. Two options are available for the
- calculation of atmospheric background:
-
- #. Average in the far field of lidar channel. In this case the value
- of this variable has to be 1
-
- #. Average within pre-trigger bins. In this case the value of this
- variable has to be 0
-
- This information can be also taken from SCC\_DB. Let’s suppose in our
- example we use the pre-trigger for the 1064nm channel and the far
- field for all other channels. In this case we have to set:
-
- ::
-
- Background_Mode = 0, 1, 1, 1 ;
-
-Background_Low(channels)
- This mandatory array defines the minimum altitude (in meters) to
- consider in calculating the atmospheric background for each channel.
- In case pre-trigger mode is used the corresponding value has to be
- set to the rangebin to be used as lower limit (within pre-trigger
- region) for background calculation. In our example, if we want to
- calculate the background between 30000 and 50000 meters for all
- photoncounting channels and we want to use the first 500 pre-trigger
- bins for the background calculation for the 1064nm channel we have to
- set:
-
- ::
-
- Background_Low= 0, 30000, 30000, 30000 ;
-
-Background_High(channels)
- This mandatory array defines the maximum altitude (in meters) to
- consider in calculating the atmospheric background for each channel.
- In case pre-trigger mode is used the corresponding value has to be
- set to the rangebin to be used as upper limit (within pre-trigger
- region) for background calculation. In our example, if we want to
- calculate the background between 30000 and 50000 meters for all
- photoncounting channels and we want to use the first 500 pre-trigger
- bins for the background calculation for the 1064nm channel we have to
- set:
-
- ::
-
- Background_High = 500, 50000, 50000, 50000 ;
-
-Molecular_Calc
- This mandatory variable defines the way used by SCC to calculate the
- molecular density profile. At the moment two options are available:
-
- #. US Standard Atmosphere 1976. In this case the value of this
- variable has to be 0
-
- #. Radiosounding. In this case the value of this variable has to be 1
-
- If we decide to use the option 1. we have to provide also the
- measured pressure and temperature at lidar station level. Indeed if
- we decide to use the option 2. a radiosounding file has to be
- submitted separately in NetCDF format (the structure of this file is
- summarized in table tab:sounding). Let’s suppose we want to use the
- option 1. so:
-
- ::
-
- Molecular_Calc = 0 ;
-
-Pressure_at_Lidar_Station
- Because we have chosen the US Standard Atmosphere for calculation of
- the molecular density profile we have to give the pressure in hPa at
- lidar station level:
-
- ::
-
- Pressure_at_Lidar_Station = 1010 ;
-
-Temperature_at_Lidar_Station
- Because we have chosen the US Standard Atmosphere for calculation of
- the molecular density profile we have to give the temperature in C at
- lidar station level:
-
- ::
-
- Temperature_at_Lidar_Station = 19.8 ;
-
-Depolarization_Factor(channels)
- This array is required only for lidar systems that use the two
- depolarization channels for the backscatter retrieval. It represents
- the factor :math:`f` to calculate the total backscatter signal
- :math:`S_t` combining its cross :math:`S_c` and parallel
- :math:`S_p` components: :math:`S_t=S_p+fS_c`. This factor is
- mandatory only for systems acquiring :math:`S_c` and :math:`S_p`
- and not :math:`S_t`. For systems acquiring :math:`S_c`,
- :math:`S_p` and :math:`S_t` this factor is optional and it will
- be used only for depolarizaton ratio calculation. Moreover only the
- values of the array corresponding to cross polarization channels will
- be considered; all other values will be not taken into account and
- should be set to undefined value. In our example for the wavelength
- 532nm we have only the cross and the parallel components and not the
- total one. So we have to give the value of this factor only in
- correspondence of the 532nm cross polarization channel that
- corresponds to the channel index 1. Suppose that this factor is 0.88.
- Moreover, because we don’t have any other depolarization channels we
- have also to set all other values of the array to undefined value.
-
- ::
-
- Depolarization_Factor = _,0.88,_,_ ;
-
-LR_Input(channels)
- This array is required only for lidar channels for which elastic
- backscatter retrieval has to be performed. It defines the lidar ratio
- to be used within this retrieval. Two options are available:
-
- #. The user can submit a lidar ratio profile. In this case the value
- of this variable has to be 0.
-
- #. A fixed value of lidar ratio can be used. In this case the value
- of this variable has to be 1.
-
- If we decide to use the option 1. a lidar ratio file has to be
- submitted separately in NetCDF format (the structure of this file is
- summarized in table tab:lr). If we decide to use the option 2. the
- fixed value of lidar ratio will be taken from SCC\_DB. In our example
- we have to give a value of this array only for the 1064nm lidar
- channel because for the 532nm we will be able to retrieve a Raman
- backscatter coefficient. In case we want to use the fixed value
- stored in SCC\_DB we have to set:
-
- ::
-
- LR_Input = 1,_,_,_ ;
-
-DAQ_Range(channels)
- This array is required only if one or more lidar signals are
- acquired in analog mode. It gives the analog scale in mV used to
- acquire the analog signals. In our example we have only the 1064nm
- channel acquired in analog mode. If we have used a 100mV analog scale
- to acquire this channel we have to set:
-
- ::
-
- DAQ_Range = 100,_,_,_ ;
-
-Global attributes
-~~~~~~~~~~~~~~~~~
-
-Measurement_ID
- This mandatory global attribute defines the measurement ID
- corresponding to the actual lidar measurement. It is a string
- composed by 12 characters. The first 8 characters give the start date
- of measurement in the format YYYYMMDD. The next 2 characters give the
- Earlinet call-sign of the station. The last 2 characters are used to
- distinguish between different time-series within the same date. In
- our example we have to set:
-
- ::
-
- Measurement_ID= "20090130cc00" ;
-
-RawData_Start_Date
- This mandatory global attribute defines the start date of lidar
- measurements in the format YYYYMMDD. In our case we have:
-
- ::
-
- RawData_Start_Date = "20090130" ;
-
-RawData_Start_Time_UT
- This mandatory global attribute defines the UT start time of lidar
- measurements in the format HHMMSS. In our case we have:
-
- ::
-
- RawData_Start_Time_UT = "000001" ;
-
-RawData_Stop_Time_UT``
- This mandatory global attribute defines the UT stop time of lidar
- measurements in the format HHMMSS. In our case we have:
-
- ::
-
- RawData_Stop_Time_UT = "000501" ;
-
-RawBck_Start_Date
- This optional global attribute defines the start date of dark
- measurements in the format YYYYMMDD. In our case we have:
-
- ::
-
- RawBck_Start_Date = "20090129" ;
-
-RawBck_Start_Time_UT
- This optional global attribute defines the UT start time of dark
- measurements in the format HHMMSS. In our case we have:
-
- ::
-
- RawBck_Start_Time_UT = "235001" ;
-
-RawBck_Stop_Time_UT
- This optional global attribute defines the UT stop time of dark
- measurements in the format HHMMSS. In our case we have:
-
- ::
-
- RawBck_Stop_Time_UT = "235301" ;
-
-Example of file (CDL format)
-----------------------------
-
-To summarize we have the following NetCDF Raw Lidar Data file (in CDL
-format):
-
-::
-
- dimensions:
- points = 5000 ;
- channels = 4 ;
- time = UNLIMITED ; // (10 currently)
- nb_of_time_scales = 2 ;
- scan_angles = 1 ;
- time_bck = 6 ;
- variables:
- int channel_ID(channels) ;
- int Laser_Repetition_Rate(channels) ;
- double Laser_Pointing_Angle(scan_angles) ;
- int ID_Range(channels) ;
- int Scattering_Mechanism(channels) ;
- double Emitted_Wavelength(channels) ;
- double Detected_Wavelength(channels) ;
- double Raw_Data_Range_Resolution(channels) ;
- int Background_Mode(channels) ;
- double Background_Low(channels) ;
- double Background_High(channels) ;
- int Molecular_Calc ;
- double Pressure_at_Lidar_Station ;
- double Temperature_at_Lidar_Station ;
- int id_timescale(channels) ;
- double Dead_Time(channels) ;
- int Dead_Time_Corr_Type(channels) ;
- int Acquisition_Mode(channels) ;
- double Trigger_Delay(channels) ;
- int LR_Input(channels) ;
- int Laser_Pointing_Angle_of_Profiles(time, nb_of_time_scales) ;
- int Raw_Data_Start_Time(time, nb_of_time_scales) ;
- int Raw_Data_Stop_Time(time, nb_of_time_scales) ;
- int Raw_Bck_Start_Time(time_bck, nb_of_time_scales) ;
- int Raw_Bck_Stop_Time(time_bck, nb_of_time_scales) ;
- int Laser_Shots(time, channels) ;
- double Raw_Lidar_Data(time, channels, points) ;
- double Background_Profile(time_bck, channels, points) ;
- double DAQ_Range(channels) ;
-
- // global attributes:
- :Measurement_ID = "20090130cc00" ;
- :RawData_Start_Date = "20090130" ;
- :RawData_Start_Time_UT = "000001" ;
- :RawData_Stop_Time_UT = "000501" ;
- :RawBck_Start_Date = "20090129" ;
- :RawBck_Start_Time_UT = "235001" ;
- :RawBck_Stop_Time_UT = "235301" ;
-
- data:
-
- channel_ID = 7, 5, 6, 8 ;
-
- Laser_Repetition_Rate = 50, 50, 50, 50 ;
-
- Laser_Pointing_Angle = 5 ;
-
- ID_Range = 1, 1, 1, 1 ;
-
- Scattering_Mechanism = 0, 2, 3, 1 ;
-
- Emitted_Wavelength = 1064, 532, 532, 532 ;
-
- Detected_Wavelength = 1064, 532, 532, 607 ;
-
- Raw_Data_Range_Resolution = 7.5, 15, 15, 15 ;
-
- Background_Mode = 0, 1, 1, 1 ;
-
- Background_Low = 0, 30000, 30000, 30000 ;
-
- Background_High = 500, 50000, 50000, 50000 ;
-
- Molecular_Calc = 0 ;
-
- Pressure_at_Lidar_Station = 1010 ;
-
- Temperature_at_Lidar_Station = 19.8 ;
-
- id_timescale = 1, 0, 0, 0 ;
-
- Dead_Time = _, 10, 10, 10 ;
-
- Dead_Time_Corr_Type = _, 0, 0, 0 ;
-
- Acquisition_Mode = 0, 1, 1, 1 ;
-
- Trigger_Delay = 50, 0, 0, 0 ;
-
- LR_Input = 1,_,_,_ ;
-
- DAQ_Range = 100,_,_,_ ;
-
- Laser_Pointing_Angle_of_Profiles =
- 0, 0,
- 0, 0,
- 0, 0,
- 0, 0,
- 0, 0,
- _, 0,
- _, 0,
- _, 0,
- _, 0,
- _, 0 ;
-
-
- Raw_Data_Start_Time =
- 0, 0,
- 60, 30,
- 120, 60,
- 180, 90,
- 240, 120,
- _, 150,
- _, 180,
- _, 210,
- _, 240,
- _, 270 ;
-
- Raw_Data_Stop_Time =
- 60, 30,
- 120, 60,
- 180, 90,
- 240, 120,
- 300, 150,
- _, 180,
- _, 210,
- _, 240,
- _, 270,
- _, 300 ;
-
-
- Raw_Bck_Start_Time =
- 0, 0,
- 60, 30,
- 120, 60,
- _, 90,
- _, 120,
- _, 150;
-
-
- Raw_Bck_Stop_Time =
- 60, 30,
- 120, 60,
- 180, 90,
- _, 120,
- _, 150,
- _, 180 ;
-
-
- Laser_Shots =
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _ ;
-
-
- Raw_Lidar_Data = ...
-
- Background_Profile = ...
-
-Please keep in mind that in case you submit a file like the previous one
-all the parameters present in it will be used by the SCC even if you
-have different values for the same parameters within the SCC\_DB. If you
-want to use the values already stored in SCC\_DB (this should be the
-usual way to use SCC) the Raw Lidar Data input file has to be
-modified as follows:
-
-::
-
- dimensions:
- points = 5000 ;
- channels = 4 ;
- time = UNLIMITED ; // (10 currently)
- nb_of_time_scales = 2 ;
- scan_angles = 1 ;
- time_bck = 6 ;
- variables:
- int channel_ID(channels) ;
- double Laser_Pointing_Angle(scan_angles) ;
- double Background_Low(channels) ;
- double Background_High(channels) ;
- int Molecular_Calc ;
- double Pressure_at_Lidar_Station ;
- double Temperature_at_Lidar_Station ;
- int id_timescale(channels) ;
- int Laser_Pointing_Angle_of_Profiles(time, nb_of_time_scales) ;
- int Raw_Data_Start_Time(time, nb_of_time_scales) ;
- int Raw_Data_Stop_Time(time, nb_of_time_scales) ;
- int Raw_Bck_Start_Time(time_bck, nb_of_time_scales) ;
- int Raw_Bck_Stop_Time(time_bck, nb_of_time_scales) ;
- int LR_Input(channels) ;
- int Laser_Shots(time, channels) ;
- double Raw_Lidar_Data(time, channels, points) ;
- double Background_Profile(time_bck, channels, points) ;
- double DAQ_Range(channels) ;
-
- // global attributes:
- :Measurement_ID = "20090130cc00" ;
- :RawData_Start_Date = "20090130" ;
- :RawData_Start_Time_UT = "000001" ;
- :RawData_Stop_Time_UT = "000501" ;
- :RawBck_Start_Date = "20090129" ;
- :RawBck_Start_Time_UT = "235001" ;
- :RawBck_Stop_Time_UT = "235301" ;
-
- data:
-
- channel_ID = 7, 5, 6, 8 ;
-
- Laser_Pointing_Angle = 5 ;
-
- Background_Low = 0, 30000, 30000, 30000 ;
-
- Background_High = 500, 50000, 50000, 50000 ;
-
- Molecular_Calc = 0 ;
-
- Pressure_at_Lidar_Station = 1010 ;
-
- Temperature_at_Lidar_Station = 19.8 ;
-
- id_timescale = 1, 0, 0, 0 ;
-
- LR_Input = 1,_,_,_ ;
-
- DAQ_Range = 100,_,_,_ ;
-
- Laser_Pointing_Angle_of_Profiles =
- 0, 0,
- 0, 0,
- 0, 0,
- 0, 0,
- 0, 0,
- _, 0,
- _, 0,
- _, 0,
- _, 0,
- _, 0 ;
-
-
- Raw_Data_Start_Time =
- 0, 0,
- 60, 30,
- 120, 60,
- 180, 90,
- 240, 120,
- _, 150,
- _, 180,
- _, 210,
- _, 240,
- _, 270 ;
-
- Raw_Data_Stop_Time =
- 60, 30,
- 120, 60,
- 180, 90,
- 240, 120,
- 300, 150,
- _, 180,
- _, 210,
- _, 240,
- _, 270,
- _, 300 ;
-
-
- Raw_Bck_Start_Time =
- 0, 0,
- 60, 30,
- 120, 60,
- _, 90,
- _, 120,
- _, 150;
-
-
- Raw_Bck_Stop_Time =
- 60, 30,
- 120, 60,
- 180, 90,
- _, 120,
- _, 150,
- _, 180 ;
-
-
- Laser_Shots =
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, 3000, 3000, 3000,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _,
- 1500, _, _, _ ;
-
-
- Raw_Lidar_Data = ...
-
- Background_Profile = ...
-
-This example file contains the minimum collection of mandatory
-information that has to be found within the Raw Lidar Data input
-file. If it is really necessary, the user can decide to add to these
-mandatory parameters any number of additional parameters considered in
-the previous example.
-
-Finally, suppose we want to make the following changes with respect to
-the previous example:
-
-#. use a sounding file for molecular density calculation instead of “US
- Standar Atmosphere 1976”
-
-#. supply a lidar ratio profile to use in elastic backscatter retrieval
- instead of a fixed value
-
-#. provide a overlap function for overlap correction
-
-In this case we have to generate the following NetCDF additional files:
-
-rs_20090130cc00.nc
- The name of Sounding Data file has to be computed as follows:
- ``"rs_"``+``Measurement_ID``
- The structure of this file is summarized in table tab:sounding.
-
-ov_20090130cc00.nc
- The name of Overlap file has to be computed as follows:
- ``"ov_"``+``Measurement_ID``
- The structure of this file is summarized in table tab:overlap.
-
-lr_20090130cc00.nc
- The name of Lidar Ratio file has to be computed as follows:
- ``"lr_"``+``Measurement_ID``
- The structure of this file is summarized in table tab:lr.
-
-Moreover we need to apply the following changes to the Raw Lidar Data
-input file:
-
-1. Change the value of the variable ``Molecular_Calc`` as follows:
-
- ::
-
- Molecular_Calc = 1 ;
-
- Of course the variables ``Pressure_at_Lidar_Station`` and
- ``Temperature_at_Lidar_Station`` are not necessary anymore.
-
-2. Change the values of the array ``LR_Input`` as follows:
-
- ::
-
- LR_Input = 0,_,_,_ ;
-
-3. Add the global attribute ``Sounding_File_Name``
-
- ::
-
- Sounding_File_Name = "rs_20090130cc00.nc" ;
-
-5. Add the global attribute ``LR_File_Name``
-
- ::
-
- LR_File_Name = "lr_20090130cc00.nc" ;
-
-6. Add the global attribute ``Overlap_File_Name``
-
- ::
-
- Overlap_File_Name = "ov_20090130cc00.nc" ;
