AT741 Class Project Computer Help


Updated 6 March 2002

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7 June 1995, 1812 MDT: Classic Severe Supercell Structure

This vertical cross-section is an example of what type of analysis you will be able to do with CSU-CHILL radar data. Reflectivity is contoured as marked and differential reflectivity is color shaded. The freezing/melting level is indicated by a dashed line.

Compare this with the classic Browning and Foote (1976) severe supercell model. The storm is tilted downshear with a pronounced overhang and weak echo region (or vault). The large hail cascade is defined by the areas with high reflectivity (Z > 55 dBZ) and negative Zdr (blue). CSU-CHILL storm chasers were located almost directly beneath this feature and collected hail up to 5 cm in diameter. After thin sectioning the collected hailstones, it was determined that approximately 30% of the large (D > 2 cm) hailstones contained frozen drop embryos. This is consistent with the presence of a Zdr column (Zdr > 0.5 dB above the freezing level) indicating the recirculation of supercooled rain drops into the weak echo region. It is very likely that many of these drops served as hailstone embryos.

The Computing Environment

You will have access to one Sun Workstation running Solaris 7, and three Linux Workstations. The workstations that are available for use are denali (Rm 226), longs (Rm 226), belford (Rm 226), and andes (Rm 203). Because these computers are also being used for research, we ask that priority to the workstation consoles be given to those using the machines for their research. (Note longs, and andes are located on people's desks. First use the ones that are publicly available: belford, and denali.) You will be able to remotely access the workstations.

Your disk space will be located on disks /scratch/AT741 on Belford and /u9/AT741 on Denali. The Sun Workstation, denali, can see /u9 and via automounting can also see /scratch/AT741. The Linux Workstations (shasta, belford, rainier, and longs) can see /scratch/AT741. When you log on a Sun Workstation you will end up on /u9/AT741/group*. When you log on a Linux Workstation you will end up on /scratch/AT741/group*.

IMPORTANT - Programs compiled on the Suns will not work on the Linux machines and vice-versa. You must re-compile on the appropriate machine.

Remotely Accessing the Computers

One can use ssh (ssh our_workstation) to access the group accounts on our workstations. To remotely display graphics on your Unix workstation (using X Windows), there are three things to do in order:

1) From your workstation type 'xhost +our_workstation'

2) From your workstation type 'ssh -l your_group our_workstation'

3) From our workstation type 'setenv DISPLAY your_workstation:0'

You also will need to use the xhost and setenv DISPLAY commands on Linux machines if you want to use RDSS editor while at their consoles, as editor is only available on the Suns.

Conserving Disk Space

The Sun group accounts are located on /u9/AT741/group*, where * is your group number. There is 50 Mb of space per group on the disk /u9. The Linux group accounts are located on /scratch/AT741/group*, where * is your group number. There is 10 Gb of space per group on the disk. It is strongly recommended that you use your belford's space for any large, uncompressed UF, editor, etc. files that you are currently using. Use /u9 for temporary storage of files for use on denali. From the denali you can access your belford space by 'cd belford' from your home directory on /u9. If you exceed your disk quota, you will be warned once and then some files will be deleted if you don't clean your directories. You can use 'du -k' to get your disk usage. Be sure to make liberal use of the 'gzip' UNIX command.

Using the Tape Drives

Because of the size of the radar files, you will be using our exabyte tape drives to pull files off of tape and to put files on to tape. The exabyte tape drives are available only on the machines where the tape drives reside, that is belford (Rm 226). Priority will be given to those using the machines for research. If you are not at the console of one of these machines, you must ssh to the machine.

Unix treats tape drives as if they were files. So the file name for the Belford tape drive is /dev/tape.

To pull a file off most tapes, like a CHILL tape, you first position the tape to the location of the file with 'mt fsf N', which will skip forward N files. Next you type 'dd if=/dev/tape ibs=65535 of=your_filename' to pull off the file.

To write a file or files to tape (as a tape archive), first postion your tape to the end of the files on tape by 'mt fsf N', where N is the number of tar files on tape. Next type 'tar cvf files_or_directories_to_put_on_tape' to create a tape archive on tape.

To rewind a tape, type 'mt rewind'. Note when you remove a tape from the tape drive the tape is automatically rewound. Also to check the status of a tape drive type 'mt status'.

See the web page on using local radar tools for more information.

Radar Data: Editing, Displaying, Plotting, Gridding, and Analysis Tools

For your class projects, you will have access to a variety of software packages for editing, gridding, analyzing and plotting radar data. Each groups software needs will be different depending on the subject and scope of the chosen project. At a minimum everyone will need to be able to display, edit, and plot their radar data.

Before using these tools, you should be aware of various radar data formats. Each software package usually requires one of the following specific types.

Radar Data Formats

1. UNIVERSAL FORMAT (UF): This is the most common format for radar data within our group. Data is organized in the natural coordinates for a radar [ie, spherical with azimuth angle (beam) relative to north, elevation angle (sweep), and slant range]. All data from the CSU-CHILL radar given to you on tape will be in UF format. There are several software packages that convert UF to other formats used by various analysis and plotting packages that will be discussed later.

2. NETCDF (*.cdf files): This is a standardized cartesian data format that we use for some plotting and analysis packages. Data is stored in a 3-dimensional cartesian grid (X,Y,Z). NETCDF format is used by our group to create plots with IDL and with pltgks. In order to convert a UF file into NETCDF, you need to run reorder which is discussed more later.

3. CEDRIC (*.ced files): These files are used by the CEDRIC software which is another general editting and viewing tool developed by NCAR that we primarily use for dual-Doppler synthesis of the 3-D wind field. Also, note that a CEDRIC file is actually an intermediate step between UF and NETCDF. The program CedToCDF or ced2nc converts data from CEDRIC to NETCDF format (see below).

4. DORADE (*.swp files): The radar data editing and perusal utility called solo uses a variant of the dorade data format so that each individual radar sweep is a separate file. You can convert UF files to dorade format via a script (see below).

Converting Radar Data: UF, CED, CDF, DORADE

1. UF to CEDRIC and/or NETCDF (reorder, CedToCdf): This is a multi-step process which actually produces cedric files via reorder, and then NETCDF files via CedToCdf. Here is a sample shell which converts a UF file with NETCDF as the final result. You can delete the intermediate result (e.g., the .ced file) if is not needed, which is usually the case for the purposes of this class.

#   Modify as needed
   foreach times (1904 1910 1916 1922 1928)
   set file = 'chill_7jun95_'$times
   mv $file.uf $file.tape
   /usr/local/bin/qreou < $file.inp >! $file.out
   ced2nc $file.ced
#   Optional delete
#   rm $file.ced
   mv $file.tape $file.uf
   compress $file.uf
   compress $

You need to have an input file (e.g., chill_7jun95_1904.inp) in the same directory. The following is an example using CHILL polarimetric data, a Cressman filter, and a variable radius of influence. Note that you can change the fields you wish to grid as desired. A complete description of this version of reorder and more information on setting up input files can be found in our reorder documentation ( postscript, pdf).

INPUT: "chill_7jun95_1904";
OUTPUT: "chill_7jun95_1904";
XMIN:-30.0; XMAX:40.0; XSPACING:0.5; AZRADIUS:1.0;
YMIN:-60.0; YMAX:10.0; YSPACING:0.5; ELRADIUS:1.4;
ZMIN:0.5; ZMAX:13.0; ZSPACING:0.5;
See this page for more .inp file examples that are relevant to the CHILL-Pawnee and SPOL-TOGA radar networks.

2. UF to DORADE: Here is a script that will convert UF files to DORADE format files that will be usable with solo. Note that you must input on the command line the UF file to be converted when you run this script (call it uf2dor for simplicity right now), as in "uf2dor your_file.uf". Note also that this script creates a number of dorade-format files, one for each sweep in the radar volume (There can easily be upwards of 20 sweeps in a radar volume.), thus you may want to create a special directory for any dorade files you create.

# $DISK1 will normally be $TMPDIR, but you may want
# to make it something like $TMPDIR/dorade
# to keep your main directory uncluttered
# $1 is the UF file as specified in the command line
# when this script is run 
setenv SOURCE_DEV $1
# Uncomment the following line if on Linux
# /local/usr/rdss/bin/xltrs
# Uncomment the following line if on the Suns
# /usr/local/radar/bin/xltrs

3. Regular NETCDF to vis5d-compatible NETCDF: This conversion can be accomplished by typing 'cdf2v5d outfile infile(s)'. The outfile name is whatever you choose it to be. You can have one or more files in the input category. Note that if you have more than one infile you will still only have one outfile. This way you can animate data from several radar volumes.

4. Kdp calculation: We have two programs available that can calculate specific differential phase. One is spol_uf_kdp.e and the other is chill_uf_kdp.e, developed by Larry Carey in the radarmet group. (mpplt, developed by CSU EE, is also available on the Suns.) Note that the input format is UF and the output is still UF. These scripts will create at least two new fields, specific differential phase (Kdp) and differential backscatter phase (delta), which can then be gridded, plotted,etc.

Editing, Displaying, and Plotting Radar Data

Once you have data in the proper format, then you are ready to edit, analyze, and plot. In the rest of this documentation, the input data format will be specified for each software package.

1. editor or RDSS

Input data Format: UF

Note: editor is not available on the Linux machines. To run editor on these consoles you must remotely log in to another machine, similar to if you were running editor on a machine outside the radarmet group.

2. solo

Input data format: dorade

3. pltgks

Note: Several examples of "mer" files for use are available in directory /u5/AT741/examples

To use:  pltgks example.mer XX		- X-windows
         pltgks example.mer PS		- prints to laserjet (black/white)
         pltgks example.mer PJ		- prints to deskjet (color)
         pltgks example.mer PF		- prints to a postscript file
         pltgks example.mer GF		- prints to a gif file

Input data Format: NETCDF (for radar data)

4. vis5d

Input format: NETCDF (special format, see above)

vis5d is available only on Linux machines, though the NETCDF conversion program must be run on denali or hood. Additional hard copy vis5d documentation is available from Paul Hein.

5. xv

6. cedric

Cedric the interactive version is available on the Suns, and cedric the batch version is available on the Linux machines.

Input format: CEDRIC

Cedric batch command file that works with CHILL-Pawnee network:

Cedric batch command file that works with SPOL-TOGA network: batch_2100_T2_inp.txt

7. IDL

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For additional help try consulting the Local Radar Tools Page, the Radar Meteorology Group FAQ or the Local Help Page.

This page will be updated throughout the 2002 Spring Semester.

Contact Information:

Paul Hein
Radarmet Sysop
Rm 226 Atmospheric Science
Ext. 8531