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.TH caltra
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.SH NAME
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.B caltra -
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calculate air parcel trajectories
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.SH SYNOPSIS
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.B caltra
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.I startdate
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.I enddate
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.I startfile
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.I filename
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[
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.I optional arguments
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]
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.SH DESCRIPTION
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Calculate trajectories for the air parcels starting at the positions specified in
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.I startfile.
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The trajectories cover the time period from
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.I startdate
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to
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.I enddate
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and the trajectories are saved in the output file
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.I filename.
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Forward and backward trajectories can be calculated according to the order of the start and end date.
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.SH PARAMETERS
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.TP 15
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.I startdate
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start time of the air parcels in the format YYYYMMDD_HH(MM) (e.g. 20100101_00 or 20100101_0030 for 1 January 2010, 00 UTC and 00:30 UTC). Note that the minutes (MM) are optional.
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.TP 15
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.I enddate
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end time of the air parcels (same format as the
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.I startdate
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). If the end time is after the start time, forward trajectories are calculated; otherwise, i.e. for end date before the start date, backward trajectories result.
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.TP 15
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.I startfile
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file with the starting positions of the trajectories (possibly created with
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.B
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create_strartf
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). Different formats for the "startfile" are supported (see
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.B reformat
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for details). If no format specifier (appendix .[1234]) is given, a simple (longitude,latitude,pressure) list is expected.
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.TP 15
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.I filename
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output trajectory file with trajectories. Different formats are supported (see
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.B reformat
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for details).
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.SH OPTIONAL
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.br
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.TP 15
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.I -j
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Jumping flag: if a trajectory crosses the lower boundary, it is raised a little and hence is allowed to move on. Otherwise, i.e. no "-j" flag set, the trajectory would stick at the same position. The default is that "-j" is
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.B not
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set.
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.TP 15
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.I -i hours
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time increments (in hours) for input P and S files. If not explicitely specified, this is determined from the P and S files in the current directory.
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.TP 15
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.I -t min
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time step (in minutes) for trajcetory calculation. Per default, the time step is 1/12 the time increment of the input files. For instance, 6-h input P and S files result in a time step of 5 min. The time step must be consisten with the output interval (see next optional parameter "-o").
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.TP 15
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.I -o hours
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Output interval (in minutes) of the air parcel positions. Per default it is the same as the time increment between the input P and S files (see option "-i"). Note that the output interval must be a multiple of the time step for trajectory calculation (see optional argument "-t").
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.TP 15
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.I -p
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Periodicity flag. If set, a periodic domain is assumed in zonal direction. Per default, the flag is
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.B not
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set.
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.TP 15
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.I -changet
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flag whether the times of the P and S files should be changed or not before a calculation; the default is that the
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times are
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.B not
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changed.
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.TP 15
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.I -noclean
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flag whether parameter and criterion files should be kept; this is particularly helpful for debugging.
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.TP 15
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.I -notimecheck
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take the first time on the netCDF file - do no explicit test that the requested
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time is available on the file. This is particularly helpful if you have no write
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permission for the P files.
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.SH EXAMPLES
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.TP 5
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.B [1] caltra 19891020_00 19891020_18 startf OUT.1
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Calculate forward trajectories from 20/10/1989 00 UTC to 20/10/1989 18 UTC. The starting starting positions are given on the file "startf" as a list of (longitude,latitude,pressure) values. The output trajectories are written to the file "OUT.1", where the appendix 1 denotes ASCII format..B
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.TP 5
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.B [2] caltra 19891020_18 19891020_00 startf OUT.1
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As in example 1, but backward trajectories from 20/10/1989 18 UTC to 20/10/1989 00 UTC.
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.TP 5
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.B [3] caltra 19891020_00 19891020_18 startf OUT -j
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As in example [1], but with jumping flag set: if a trajectory crosses the lower boundary (topography), it is raised a little and then is allowed to move on.
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.TP 5
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.B [4] caltra 19891020_00 19891020_18 startf OUT -j -o 15 -t 15
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As in example [3], but the output interval is set to 15 min with the optional argument "-o". Note that the output interval (15 min) must be a multiple of the time step, which is here set explicitely to 15 min with "-t".
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.TP 5
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.B [5] caltra 19891020_0130 19891020_1730 startf1 OUT -j -o 15 -t 15 -changet
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Start from non-analysis time 01:30 UTC to non-analysis time 17:30 UTC. Furthermore, the times on the prinmary netCDF files are changed accordingly.
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.SH AUTHOR
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Written by Michael Sprenger and Heini Wernli (January 2011)
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