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+++ b/docs/_build/html/_sources/netcdf_file.txt Fri May 11 13:25:05 2012 +0200
@@ -0,0 +1,1187 @@
+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" ;
