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.TH trace.SH NAME.B lidar - lidar of meteorological fields along trajectories.SH SYNOPSIS.B trace.I inpfile.I outfile[.I optional arguments].SH DESCRIPTIONGet pseudo-lidar of meteorological fields along the trajectories given in the input file.I inpfileand write the field to a netCDF file.I outfile.The horizontal axis in the netCDF file corresponds to the trajectory times, the vertical axis gives the pressure in hPa (by default, from 100 to 1000 hPa: it can be changet with optional argument '-pmin', '-pmax', '-centering'). By default, the pseudo lidar is taken at a fixed set of pressure levels between 100 and 1000 hPa. If the option '-centering' is selected, the pressure levels are relative to the trajectory position.The meteorological fields for the pseudo lidar are listed in a.Itracing file(default: tracevars). Note that the tracevars file has the same format as for.I tracebut that all online calculations in the tracing file are neglected..SH PARAMETERS.TP 15.I inpfileinput trajectory file; the appendix determines the format (see.B reformatfor details)..TP 15.I outfileoutput netCDF file for the pseudo-lidar fields..SH OUTPUT FIELDS.TP 5.B - [ FIELD_SUM | FIELD_MEAN ]Sum or mean of the lidar field FIELD, depending on the optional parameter '-sum' (default) or '-mean'. For instance, if potential temperature TH is passed as a lidar field, then TH_MEAN would contain the mean over all trajectories. The horizontal axis coincides with the times on the trajectory file; the vertical axis depends on the mode. By default, it goes from 100 hPa to 1000 hPa, within 100 steps. If '-centering' is passed as argument, the pressure levels are always relative to the trajectory position..TP 5.B - FIELD_CNTNumber of values contributing to FIELD_SUM and FIELD_MEAN. This value is variable because the following cases do not contribute to the output field FIELD_SUM/MEAN: (a) if the position is outside the data domain of the input P files; (b) if the position falls below topography; (c) if the trajectory position is invalid; and (d) if the lidar field has a missing value flag set..TP 5.B - POSITIONPosition of all trajectories contributing to the lidar composite. By default, the vertical position of the trajectories between 100 hPA and 1000 hPa can be visualised in this way. If '-centering' is selected, the POSITION corresponds to a single line because then all pressure positions are relative to the trajectory height, i.e. a pressure of 0 hPa on tghe vertical axis corresponds to the trajectory position..SH TRACING FILENormally the meteorological fields for tracing are listed in a file with name.B "tracevars".The name of the tracing file can be changed with the optional argument "-v" (see below). The format of the tracing file is as follows:.br.TP 5Format.I field.I scale.I computation.I prefix.TP 5Examples.B - TH 1. 0 S :pseudo lidar of potential temperature (TH), scale it with 1 (no scaling); it is available on the S file (no computation is needed: 0)..br.B - Q 1000. 0 P :pseudo lidar of specific humidity (Q), scale it with 1000 to have g/kg; it is available on the P file (no computation is needed: 0)..SH OPTIONAL ARGUMENTS.TP 15.TP 15.I -i hourstime 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..TP 15.I -v varfileChange the name of the tracing file from its default value "tracevars" to "varfile"..TP 15.I -f field scaleTrace field (with scaling scale) along the trajectories; the computation flag and the prefix for the data file is automatically set. This options allows the quick tracing of a field, without specifying a tracing file..TP 15.I -changetflag whether the times of the P and S files should be changed or not before a calculation; the default is that thetimes are.B notchanged..TP 15.I -nocleanflag whether parameter and criterion files should be kept; this is particularly helpful for debugging..TP 15.I -timecheckenforce a time check on the data files.TP 15.I -nearestDo no interpolation between grid points; just take the nearest neighbor! This option is useful, if a discrete input field is given (e.g. labels), where interpolated values are meaningless..TP 15.I [-sum|-mean]If '-sum' (the default) is chosen and several trajectories are on the input file, then the sum of all pseudo lidar fields is written to the output file; otherwise, for '-mean', the mean of all pseudo lidar fields is written..TP 15.I -zmin valueSet the lower limit for the pseudo lidar. Default is 100 m..TP 15.I -zmax valueSet the upper limit for the pseudo lidar. Default is 10'000 m..TP 15.I -nlev valueSet the number of pressure levels between 'zmin' and 'zmax. Default is 100..TP 15.I -centeringSelect the pressure levels relative to the trajectory position; by default the pressure levels are given as absolute heights between 100 and 1000 hPa. If '-centering' is chosen and no explicit limits are specified with 'pmin' and 'pmax', the limits are set to pmin=-500 hPa and pmax=500 hPa..SH VECTOR FIELDSNote for lidaring of vector fields, e.g wind (U,V), there are two options:.TP 5- the lidar variable in the tracing field can be given as U, for instance, and then the component U will be lidared along the trajectory; but this U is the wind component in the rotated coordinate system, i.e. the zonal wind along the rotated latitude circles!.TP 5- if the lidar variable is specified as U.V, a vectorial transformation is applied, i.e. the wind components are transformed into true zonal and meridional wind components. This option is physically more meaningful!.SH EXAMPLES.TP 5.B [1] lidar TRAJECTORY.1 LIDARRead the trajectory file TRAJECTORY.1 and get a composite pseudo-lidar from 100 to 1000 hPa along the the trajectories. If there are several trajectories on TRAJECTORY.1, the sum is written to the netCDF file LIDAR. The fields of which a pseudo lidar is calculated are listed in the file 'tracevars'..TP 5.B [2] lidar TRAJECTORY.1 LIDAR -zmin 200 -zmax 500As in [1], but the upper and lower limits of the pseudo lidar are set to 200 and 500 m..TP 5.B [3] lidar TRAJECTORY.1 LIDAR -centeringAs in [1], but the lidar pressure levels are not fixed: They are taken relative to the trajectory height..TP 5.B [4] lidar TRAJECTORY.1 LIDAR -f U.V 1.The wind (U,V) is 'lidared' along the trajectory; the two component U and V are treated as part of a vector (U,V) and the components are transformed into true zonal and meridional winds..SH AUTHORWritten by Michael Sprenger and Heini Wernli (April 2012).