GEMPAK Manual |
Programs
DCNLDN (Unidata)
DCNLDN decodes NLDN lightning data reports from a real-time data
feed, or from a file fed to the program through standard input, and
writes the data to a GEMPAK ship format file. The program is
controlled by inputs to the command line. Each NLDN report contains
the date, time, and location of the flash along with the requested
data values. Available data include: TSEC (Seconds since STIM
(station time)), MSEC (Milliseconds since TSEC), SGNL (Signal
strength and polarity where 150 units corresponds to approximately
30 KAmps), MULT (Multiplicity in strokes/flash), SMAJ (Semi-major axis
of ellipse), ECNT (Eccentricity of ellipse), ANGL (Angle in degrees),
and CHI2 (Chi-squared confidence measure). Which of the data values are
stored is determined by the parameter packing file. The STID field of the
GEMPAK surface file will contain a "+" character for positive SGNL values
and a "-" character for negative SGNL values.
The inputs are program options, and the output file name or template.
For example, for real-time data feeds:
dcnldn [options] output_file
For archived data
dcnldn [options] output_file < input_file
A template may be used to specify the output file name. The file
name template uses the date and time of the bulletin or report
to replace the following characters.
YY Year without the century
MM Month number
DD Day
HH Hour
NN Minute
@@ File Sequence Number
Because the number of lightning strikes that may occur in a
single hour can be very large, it is possible that the number
of strikes will exceed the size of the output file. By default,
when the size of the output file is exceeded, a new file is created
and a sequence number _## is appended to the file name, where
## is 01 for the first additional file created, 02 for the
second, etc.
The user may use the @@ template option to tailor the sequence
numbering to suite local tastes. When using @@, the initial file
will be numbered 00.
The default file size that will be created by dcnldn is 25,000.
Typical summer conditions may exceed 25,000 a few hours during the day.
The -m option may be used to create smaller files, which will be
more space efficient during less active periods.
By default, strikes are assigned hourly DATTIM stamps. The user
may specify data to be binned in NN minute bins by specifying
the storage method using the "-s minuteNN" option. For
example minute06 will generate DATTIMs with YYMMDD/HH00, YYMMDD/HH06,
YYMMDD/HH12, ... times.
The GEMPAK data file created by dcnldn is a SHIP-type surface file,