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Frequently asked questions
==========================

  Is it necessary to provide only measurment periods with cloud free conditions and 
  homogeneous atmosphere or is this part of ELDA or the pre processing of the data? 
  For example in cases with scattered low cumulus clouds.

At moment you should provide cloud free data because the automatic cloud screening 
is not yet implemented in the SCC. We are working on this issue and hopefully the new 
module will be implemented at the end of ACTRIS project . 

  What is the definition of low range, ultra near range and high range channels? 
  Are there any threshold values?

There are no threshold values defined for the different range types. This information 
is used only in the gluing procedures just to identify which channel should be taken 
as low range and which one as far range. If no gluing is applied by the SCC the range 
id flags are not taken into account.

   Due to changes in the settings of our lidarsystem, the depolarization factor can 
   change during the measurement. Is it necessary to provide one SCC-file for each settings 
   or is it possible to set the Depolarization_Factor variable time dependent? 
   
Unfortunately it is not possible to have time dependence on Depolarization_Factor variable. 
So if this parameter changes you should provide different SCC files for each setting.

   Is it possible for documentation purposes to put own parameters in the SCC-NetCDF file? 
   For example who created the file.... Are there any reasons against this? 

Technically as long as you use not standard SCC variables for your own parameters there are
no problems for the SCC. It will just ignore these not standard variables.
 
   Which NetCDF version is to use? NetCDF3, NetCDF3 Classic, NetCDF4, NetCDF4 Classic? 

The NetCDF libraries 4.1.3 are used in all the SCC modules. So all the NetCDF formats you 
have indicated should be compatible with the SCC (we have tested NetCDF3 and NetCDF4).

   What are the values for the lidar ratio used in the SCC_DB? 

The values of (fixed) lidar ratio used by the SCC in the elastic retrieval can be set by 
the user using the SCC web interface. In particular you can define a lidar ratio value for 
each elastic backscatter product: in the product page there is the section “Elastic Backscatter 
options” in which there is the field “Fixed lr”. In case you want to use a lidar ratio profile 
you should set LR_Input accordingly and provide an external LR profile NetCDF file 
(see documentation on SCC file format).

   In cases of measurements where Raman channels are available, the SCC will calculate the Raman 
   backscatter profile. If I want to retrieve Klett-retrievals for this channel, too (e.g 532nm) 
   is it sufficient to set the value in LR_input(channels) to 1 or 0 plus a LR-profile to get 
   both retrievals? 

No. In general, for each lidar configuration you can define a set of optical products to be calculated 
for that configuration using the SCC web interface. So suppose you have a system with 532nm and 607nm 
channels. In this case you have 2 options:
#. Raman backscatter and extinction in the e532 file and Raman backscatter (full resolution) in the b532 
file. In this case you should associate to the configuration a product of type “lidar ratio and  will 
produce the e532 file and a product of type “Raman backscatter” which will produce the b532 file
#. Raman backscatter and extinction in the e532 file and elastic backscatter in the b532 file. 
In this case you should associate to the configuration a product of type “lidar ratio and extinction” 
which will produce the e532 file and a product of type “elastic backscatter” which will produce the b532 file

Note: you cannot calculate a b532 file containing the Raman and elastic backscatters at the same time. 
The reason is that the 2 products will produce an output file with the same name (according to the EARLINET rules). 
Moreover in general, it makes no sense to calculate the elastic backscatter when you can calculate the Raman 
one which usually is better.

   What are the conventions for the filnames for the various files that need to be uploaded?

The following definitions apply:   
- SCC raw lidar data file

This file should be named as measID.nc. For example if your measurement had a measurementID of 20130101cc00 the corresponding NetCDF file should be named 20130101cc00.nc 

- Sounding file

The file should be named as rs_measID.nc. Considering the above example the sounding file should be named rs_20130101cc00.nc

In this case you should also set the global attribute Sounding_File_Name in the raw lidar data file as:

Sounding_File_Name=rs_20130101cc00.nc

- Lidarration file

The file should be named as lr_measID.nc. Considering the above example the sounding file should be named lr_20130101cc00.nc

In this case you should also set the global attribute LR_File_Name in the raw lidar data file as:

LR_File_Name=lr_20130101cc00.nc

- Overlap file

The file should be named as ov_measID.nc. Considering the above example the sounding file should be named ov_20130101cc00.nc

In this case you should also set the global attribute Overlap_File_Name in the raw lidar data file as:

Overalp_File_Name=ov_20130101cc00.nc