docs/faq/faq.rst

Tue, 19 Feb 2013 20:50:16 +0200

author
Giannis <binietoglou@imaa.cnr.it>
date
Tue, 19 Feb 2013 20:50:16 +0200
changeset 23
fa3549c8ebea
child 24
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permissions
-rw-r--r--

Added a basic FAQ (not checked for format, not added to index.rst)

binietoglou@23 1 Frequently asked questions
binietoglou@23 2 ==========================
binietoglou@23 3
binietoglou@23 4 Is it necessary to provide only measurment periods with cloud free conditions and
binietoglou@23 5 homogeneous atmosphere or is this part of ELDA or the pre processing of the data?
binietoglou@23 6 For example in cases with scattered low cumulus clouds.
binietoglou@23 7
binietoglou@23 8 At moment you should provide cloud free data because the automatic cloud screening
binietoglou@23 9 is not yet implemented in the SCC. We are working on this issue and hopefully the new
binietoglou@23 10 module will be implemented at the end of ACTRIS project .
binietoglou@23 11
binietoglou@23 12 What is the definition of low range, ultra near range and high range channels?
binietoglou@23 13 Are there any threshold values?
binietoglou@23 14
binietoglou@23 15 There are no threshold values defined for the different range types. This information
binietoglou@23 16 is used only in the gluing procedures just to identify which channel should be taken
binietoglou@23 17 as low range and which one as far range. If no gluing is applied by the SCC the range
binietoglou@23 18 id flags are not taken into account.
binietoglou@23 19
binietoglou@23 20 Due to changes in the settings of our lidarsystem, the depolarization factor can
binietoglou@23 21 change during the measurement. Is it necessary to provide one SCC-file for each settings
binietoglou@23 22 or is it possible to set the Depolarization_Factor variable time dependent?
binietoglou@23 23
binietoglou@23 24 Unfortunately it is not possible to have time dependence on Depolarization_Factor variable.
binietoglou@23 25 So if this parameter changes you should provide different SCC files for each setting.
binietoglou@23 26
binietoglou@23 27 Is it possible for documentation purposes to put own parameters in the SCC-NetCDF file?
binietoglou@23 28 For example who created the file.... Are there any reasons against this?
binietoglou@23 29
binietoglou@23 30 Technically as long as you use not standard SCC variables for your own parameters there are
binietoglou@23 31 no problems for the SCC. It will just ignore these not standard variables.
binietoglou@23 32
binietoglou@23 33 Which NetCDF version is to use? NetCDF3, NetCDF3 Classic, NetCDF4, NetCDF4 Classic?
binietoglou@23 34
binietoglou@23 35 The NetCDF libraries 4.1.3 are used in all the SCC modules. So all the NetCDF formats you
binietoglou@23 36 have indicated should be compatible with the SCC (we have tested NetCDF3 and NetCDF4).
binietoglou@23 37
binietoglou@23 38 What are the values for the lidar ratio used in the SCC_DB?
binietoglou@23 39
binietoglou@23 40 The values of (fixed) lidar ratio used by the SCC in the elastic retrieval can be set by
binietoglou@23 41 the user using the SCC web interface. In particular you can define a lidar ratio value for
binietoglou@23 42 each elastic backscatter product: in the product page there is the section “Elastic Backscatter
binietoglou@23 43 options” in which there is the field “Fixed lr”. In case you want to use a lidar ratio profile
binietoglou@23 44 you should set LR_Input accordingly and provide an external LR profile NetCDF file
binietoglou@23 45 (see documentation on SCC file format).
binietoglou@23 46
binietoglou@23 47 In cases of measurements where Raman channels are available, the SCC will calculate the Raman
binietoglou@23 48 backscatter profile. If I want to retrieve Klett-retrievals for this channel, too (e.g 532nm)
binietoglou@23 49 is it sufficient to set the value in LR_input(channels) to 1 or 0 plus a LR-profile to get
binietoglou@23 50 both retrievals?
binietoglou@23 51
binietoglou@23 52 No. In general, for each lidar configuration you can define a set of optical products to be calculated
binietoglou@23 53 for that configuration using the SCC web interface. So suppose you have a system with 532nm and 607nm
binietoglou@23 54 channels. In this case you have 2 options:
binietoglou@23 55 #. Raman backscatter and extinction in the e532 file and Raman backscatter (full resolution) in the b532
binietoglou@23 56 file. In this case you should associate to the configuration a product of type “lidar ratio and will
binietoglou@23 57 produce the e532 file and a product of type “Raman backscatter” which will produce the b532 file
binietoglou@23 58 #. Raman backscatter and extinction in the e532 file and elastic backscatter in the b532 file.
binietoglou@23 59 In this case you should associate to the configuration a product of type “lidar ratio and extinction”
binietoglou@23 60 which will produce the e532 file and a product of type “elastic backscatter” which will produce the b532 file
binietoglou@23 61
binietoglou@23 62 Note: you cannot calculate a b532 file containing the Raman and elastic backscatters at the same time.
binietoglou@23 63 The reason is that the 2 products will produce an output file with the same name (according to the EARLINET rules).
binietoglou@23 64 Moreover in general, it makes no sense to calculate the elastic backscatter when you can calculate the Raman
binietoglou@23 65 one which usually is better.
binietoglou@23 66
binietoglou@23 67 What are the conventions for the filnames for the various files that need to be uploaded?
binietoglou@23 68
binietoglou@23 69 The following definitions apply:
binietoglou@23 70 - SCC raw lidar data file
binietoglou@23 71
binietoglou@23 72 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
binietoglou@23 73
binietoglou@23 74 - Sounding file
binietoglou@23 75
binietoglou@23 76 The file should be named as rs_measID.nc. Considering the above example the sounding file should be named rs_20130101cc00.nc
binietoglou@23 77
binietoglou@23 78 In this case you should also set the global attribute Sounding_File_Name in the raw lidar data file as:
binietoglou@23 79
binietoglou@23 80 Sounding_File_Name=rs_20130101cc00.nc
binietoglou@23 81
binietoglou@23 82 - Lidarration file
binietoglou@23 83
binietoglou@23 84 The file should be named as lr_measID.nc. Considering the above example the sounding file should be named lr_20130101cc00.nc
binietoglou@23 85
binietoglou@23 86 In this case you should also set the global attribute LR_File_Name in the raw lidar data file as:
binietoglou@23 87
binietoglou@23 88 LR_File_Name=lr_20130101cc00.nc
binietoglou@23 89
binietoglou@23 90 - Overlap file
binietoglou@23 91
binietoglou@23 92 The file should be named as ov_measID.nc. Considering the above example the sounding file should be named ov_20130101cc00.nc
binietoglou@23 93
binietoglou@23 94 In this case you should also set the global attribute Overlap_File_Name in the raw lidar data file as:
binietoglou@23 95
binietoglou@23 96 Overalp_File_Name=ov_20130101cc00.nc
binietoglou@23 97
binietoglou@23 98
binietoglou@23 99
binietoglou@23 100

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