# HG changeset patch # User Giannis # Date 1361299816 -7200 # Node ID fa3549c8ebeacafdd9e998de2633f1919135a19a # Parent 819d26010f63e97f9abfc30d3d64febb3fb7edd0 Added a basic FAQ (not checked for format, not added to index.rst) diff -r 819d26010f63 -r fa3549c8ebea docs/faq/faq.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/docs/faq/faq.rst Tue Feb 19 20:50:16 2013 +0200 @@ -0,0 +1,100 @@ +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 + + + +