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uacalplt - Upper air calculation and plotting program


uacalplt [parameters...] filename


Command Line Resource Default Description
-h help No Lists basic help information.
-df=filename default .wxpdef Sets the name of the resource file.
-na=name name uacalplt Specifies the name used in resource file parsing.
-ba batch No Run program in batch mode
-me=level message out2 Specifies level of messages to be displayed
  • file information - mess
  • significant and mandatory sounding data - out1a, out1b
  • standard sounding parameters and indices - out1c, out1d
  • parcel information - out2a, out2b
  • wind parameters - out2c
  • wind level data - out3a, out3b
  • wind/storm layer data - out3c
-fp=filepath file_path current directory Specifies location of database files.  
-dp=datapath data_path current directory Specifies the location (path) of the input raw data files. This may be modified in the name convention file.
-cp=conpath con_path current directory Specifies the location (path) of the input surface converted data files. This may be modified in the name convention file.
-rp=rawpath raw_path current directory Specifies the location of the output raw files generated by the program. These files will not be generated unless the out_file resource is specified and the output is plotted data.
-ip=imagepath image_path current directory Specifies the default location of the output GIF images generated by the program.
-nc=name_conv name_conv name_conv The name convention file specifies how files are named in WXP. This sets which name convention file to use.
-if=in_file in_file upa_cvt Specifies the input file name tag. The default is upa_cvt, but it can be modified to any value in the filename convention file. A full name convention can be specified as well.
-of=out_file[,out...] out_file upa_snd Specifies what type of raw sounding file to create. By default, no output file is generated when the program. This specifies an output file name tag. The default is upa_snd. A full filename can be specified which can contain name convention tags.
-cu=[hour|la] current None This specifies to use current data files. The current filename is based on the name convention. An optional hour can be specified for older data. If la is specified, the program will search back to find the most recent available file.
-ho=hour hour None This resource specifies the exact hour that a data file is valid for. This locks in the start hour for a multi-file sequence.
-id=identifier identifier None Specifies the station to use in the program.Used to plot a specific observation. If not specified, all stations will be plotted.
-pd=domain plot_domain None.
Full plot
This specifies the plotting domain. The projection, aspect ratio and the domain size are specified.
-pl=plot_type plot_type User prompt
Batch: skewt
Specifies the type of output thermodynamic plot. By default, this is a Skew T diagram.  The available plot types are:
  • skewt -- Skew T log P diagram
  • ema -- Emagram
  • stuve -- Stuve diagram
  • hodo -- Hodogram
  • none -- for no output plot
-sc=scale_factor plot_scale 1.0 Specifies a scaling factor for all plotted text, symbols, vectors, etc.
-fm=format plot_format None Specifies the output format of the plots.  This is generally used to specify how many decimal places get displayed on the plot and in the output raw files.
-pp=param[,param...] plot_param None Specifies additional plotting parameters. See the plot_param resource for more details.
-dr=drawable[,...] draw all Specifies which part of the plot is to be drawn.
-la=label[,...] label Program defaults Specifies the labels to be plotted around the plot. By default, labels are generated by the program and plotted above and below the plot. This resource overrides these labels.
-fl=font_list font_list modern.fnt Specifies a list of fonts to use in the plots.
-ct=color_table color_table wxp.clr Specifies the color table to use in the plot. This maps color names to actual RGB color values.
-cot=color[:attr] color_text white
for inverse plots.
Specifies the text color for labels above and below the plot.
-coth=color[:attr] color_therm blue, blue, green, cyan, yellow This resource is used to specify the color and attributes for the thermodynamic plot. There are 5 possible values:
  1. pressure lines (default blue)
  2. temperature lines (default blue)
  3. potential temperature lines -- dry adiabats (default green)
  4. equivalent potential temperature lines -- moist adiabats (default cyan)
  5. mixing ratio lines (default yellow or brown on inverse color plots)
-cott=color[:attr] color_thrmtxt lblue, lblue, off, off, yellow This resource is used to specify the color and attributes for the labels on the thermodynamic plot. There are 5 possible values:
  1. pressure lines (default blue)
  2. temperature lines (default blue)
  3. potential temperature lines -- dry adiabats (default off - does not plot normally)
  4. equivalent potential temperature lines -- moist adiabats (default off - does not plot normally)
  5. mixing ratio lines (default yellow or brown on inverse color plots)
-cosd=color[:attr] color_sound white, white, yellow This resource is used to specify the color and attributes for the sounding plot. There are 3 possible values:
  1. temperature sounding (default white or black for inverse plots)
  2. dewpoint sounding (default white or black for inverse plots)
  3. parcel sounding (default yellow or brown on inverse color plots)
-cowd=color[:attr] color_wind white
for inverse plots.
Specifies the color for wind barbs on thermodynamic plots.
-coho=color[:attr] color_hodo blue, blue, white, cyan, red This resource is used to specify the color and attributes for the hodograph plot. There are 5 possible values:
  1. direction lines (default blue)
  2. speed circles (default blue)
  3. sounding line up to 700 mb (default white or black for inverse plots)
  4. sounding line above 700 mb (default cyan)
  5. marker "+" denoting each level (default red)
-coht=color[:attr] color_hodtxt lblue, lblue, lred This resource is used to specify the color and attributes for the labels on the hodograph plot. There are 3 possible values:
  1. direction labels (default lblue)
  2. speed labels (default lblue)
  3. sounding labels denoting pressure level (default lred)
-de=device[,...] device User prompt
Batch: display
Specifies the output device.
-ti=title title Program name Specifies the window title.
-ic icon Off Specifies whether to open window in iconified mode.
-bg=color background black
white for inverse plots
Specifies the background color of the window.
-ge=geometry geometry 640x480 Specifies the window and paper geometry.
filename[#seq] filename None
User Pompt
Batch: current=la
The name of the upper air converted data file to be plotted. An optional sequence number can be added to designate the time for non-WXP files.


This program plots upper air sounding data on a thermodynamic diagram or hodograph. The input to the program is a upper air converted file produced by the uacvt programs.

The programs starts off by prompting the user for input converted file name.  The user may specify the input file either via the command line of through the current resource. The input naming convention is specified by the upa_cvt tag but this can be changed with the in_file resource.

Next, the user enters a station identifier. A list of available stations from the converted file is displayed. The stations are listed by their 3/4 letter IDs and not the 5 digit WMO number for ease of selection. Once the station is selected, the program prints out sounding information, and standard sounding parameters and indices.

Text Output

The first section is the station location information which is printed at message level out1a:

Date:0000Z 30 SEP 97
Station: ILX
WMO ident:  74560
Latitude:   40.15
Longitude: -89.33
Elevation: 178.00

The next section is the raw sounding data. This is a merged set of mandatory and significant level data.  Additional computations are performed.  Here is a list of the columns printed (all printed at mess level out1a [see red text] unless specified)

  • LEV -- level number. Special levels are denoted with SFC (surface), TRP (tropopause), WND (max wind).
  • PRES -- pressure of level in mb
  • HGHT -- geopotential height in m (intermediate levels interpolated using hypsometric approximation)
  • TEMP -- temperature in C
  • DEWP -- dewpoint in C
  • RH -- relative humidity in %
  • DD -- dewpoint depression in C (mess level out1b)
  • WETB -- wetbulb temperature in C (mess level out1b)
  • DIR -- wind direction in deg (intermediate levels interpolated using significant wind level data)
  • SPD -- wind speed in knt (intermediate levels interpolated using significant wind level data)
  • THETA -- potential temperature in K (mess level out1b)
  • THE-V -- virtual potential temperature in K (mess level out1b)
  • THE-W -- wetbulb potential temperature in K (mess level out1b)
  • THE-E -- equivalent potential temperature in K (mess level out1b)
     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg
  0 1000    -1                                                                 
SFC  980   178  26.4   6.4  28 20.0  14.7 280  19 301.3 302.4 288.6 319.7  6.15
  2  925   678  22.2   2.2  27 20.0  11.3 280  47 302.0 302.9 287.6 316.6  4.85
  3  850  1403  15.2  -0.8  33 16.0   7.1 280  46 302.1 302.8 287.1 315.0  4.24
  4  700  3001   0.0  -6.0  64  6.0  -2.6 295  50 302.5 303.1 286.5 313.2  3.49

The next section displays standard sounding parameters and indices. Most of the information is printed at message level out1d except for thickness, lifted, Showalter, total totals and K indices which is at message level out1c (red text).

Sounding variables and indices
1000-500 mb thick:      5631.00 m
Freezing level:          700.00 mb =  3001.00 m =  9845.68 ft
Wetbulb zero:            740.60 mb =  2536.94 m =  8323.18 ft
Precipitable water:        0.65 inches
Sfc-500 mean rel hum:     36.73 %
Est. max temperature:     27.28 C =   81.10 F
Sfc-Lift cond lev (LCL): 729.89 mb =  2656.89 m =  8716.74 ft T: 3.27 C
700-500 lapse rate:        4.68 C/km
ThetaE index:             11.23 C Layer  925.0- 598.0 mb
Conv cond level (CCL):   689.45 mb =  3121.77 m = 10241.90 ft
  Mean mixing ratio:       5.11 g/kg
  Conv temperature:       27.64 C =   81.75 F
Cap Strength:              3.86 C
Lifted Index:              5.67 C Risk: None
Lifted Index @300 mb:      7.03 C
Lifted Index @700 mb:      0.59 C
Showalter Index:           6.96 C Risk: None
Total Totals Index:       39.00 C Risk: None
  Vertical Totals Index:  27.50 C
  Cross Totals Index:     11.50 C
K Index:                  20.70   Risk: 20-40 % chance of thunderstorms
Sweat Index:             178.00   Risk: None
Energy Index:              1.12   Risk: None

The next section involves a parcel trajectory. The parcel is taken from some initial condition and raised vertically to the top of the sounding. The default parcel uses a 100 mb mean layer above the surface. The parcel type can be changed with the par plot parameter:


Temperature and dewpoint are optional. If not specified, the sounding temperature
and dewpoint are used.

Type   Pres   Temp  Dew
pressure level   pres  temp   dew
surface level   sfc   temp dew
max temperature   maxt   --   --
pressure layer   layer   thick   --

The data are printed at message level out2b except for CAPE, convective inhibition and cap strength which is printed at level out2a (red text).

Parcel Indices
Parcel: using 100 mb layer
CAPE (B+):                10.89 J/kg
Max Up Vert Vel:           4.67 m/s
Conv Inhibition (B-):     30.45 J/kg
Cap Strength:              5.49 C
Lift Cond Lev (LCL):     696.21 mb =  3044.15 m =  9987.25 ft
Lev Free Conv (LFC):     681.21 mb =  3217.42 m = 10555.70 ft
Equ Level (EL):          631.21 mb =  3818.50 m = 12527.73 ft
B at Equ Level:            7.84 J/kg
Max Parcel Lev (MPL):    611.21 mb =  4071.09 m = 13356.44 ft

The next section displays significant wind level data. Storm relative winds are computed based on a mean storm motion. This is computed using the mean wind of the lower 6km of the atmosphere. The storm direction is deflected 30 deg clockwise and the speed is 75% of the 6km mean speed. The output is at message level out3a (red text) except for the storm relative winds which is at out3b.

Wind level data
   Storm motion: 325 at  43 knt
                   TRUE/GROUND REL   |     STORM REL
 LEV   P    H    DIR SPD   U     V   | DIR SPD   U     V
       mb   m        knt     m/s     |     knt     m/s
  0   980   178  280  19  18.7  -3.3 | 170  32  -5.6  31.9 
  1   966   305  280  30  29.5  -5.2 | 190  30   5.3  30.0 
  2   932   610  275  46  45.8  -4.0 | 215  38  21.6  31.2 
  3   925   678  280  47  46.3  -8.2 | 219  35  22.0  27.0 

The next section is wind parameters and indices. This is printed at message level out2d except for mean winds, storm direction, helicity and energy-helicity index which are at level out2c (red text)

Wind Parameters
Mean winds (0-6000m):            295.4 at   57.0 knts
Storm direction:                 325.4 at   42.8 knts
Shear (0-3000m)              pos:    2.6 neg:    4.7 tot:    7.3 10-3/s
Storm rel Dir Shear (0-3000m):      69.6 deg
Storm rel helicity (0-3000m) pos:  310.7 neg:   -7.0 tot:  303.7 m^2/s^2
                             ave:  101.2 10^-3 m/s^2 rel:   0.84
Storm rel vorticity (0-3000m) horiz:    8.0 stream:    6.7 10^-3/s
Energy-Hel index:          0.02
Bulk Rich Number:          0.13
Bulk Shear:               85.84 m/s

The next section shows storm layer parameters.  All of this information is printed at message level out3c.

Storm Parameters
Depth  Mean    Inflow|    Shear      |           Helicity           | Vorticity
 AGL  Dir Spd Dir Spd|  Pos  Neg  Tot|  Pos   Neg   Tot   Ave   Rel |  Hor Strm
  m       knt     knt|     10^-3/s   |       m^2/s^2     m/s^2      | 10^-3/s
 500  278  36 200  32|  0.0 28.8 28.8|225.6   0.0 225.6  451.2  1.00| 29.7 29.6
1000  279  41 210  33|  0.0 14.0 14.0|225.6  -7.0 218.6  218.6  0.94| 15.3 14.4
1500  280  43 213  33|  0.9  9.3 10.2|229.6  -7.0 222.6  148.4  0.88| 11.1  9.8
2000  281  44 215  33|  1.1  7.0  8.1|249.4  -7.0 242.5  121.2  0.89|  9.0  7.9
2500  282  45 217  32|  1.7  5.6  7.3|280.2  -7.0 273.2  109.3  0.89|  8.0  7.1
3000  284  45 219  31|  2.6  4.7  7.3|310.7  -7.0 303.7  101.2  0.84|  8.0  6.7
4000  289  47 225  28|  2.8  4.6  7.3|351.2  -7.0 344.3   86.1  0.75|  7.9  6.0
5000  294  51 237  26|  3.3  4.6  7.9|458.4  -7.0 451.4   90.3  0.73|  8.5  6.2
6000  295  57 248  29|  2.7  5.6  8.4|458.4-100.4 358.0   59.7  0.50|  9.0  4.5

Sounding Plots

After the text is displayed, the user is prompted for the output plot type. The selections are:

  • skewt -- Skew T log P diagram
  • ema -- Emagram
  • stuve -- Stuve diagram
  • hodo -- Hodogram

A thermodynamic diagram is plot showing the temperature and dewpoint plotted versus pressure (or height).  A hodograph is a plot of wind speed versus direction on a polar grid.

Skew-T log-P: The skew-T log-P diagram is an energy conserving diagram in which the temperature and potential temperature lines are nearly perpendicular. The pressure lines are plotted horizontally in blue and are also on an inverse log scale. The concept of Skew T means that the temperature is not plotted vertically but angles off to the right at a 45 degree angle. The temperature lines of the Skew T are in blue. The dry adiabats slope off to the upper left and are plotted in green. The light blue dashed curved lines are saturation adiabats. The yellow dashed lines are lines of constant mixing ratio.

The sounding is displayed in white, with the white line on the left of the plot representing the dewpoint line and the white data line on the right representing the temperature line. When printed, these are bold lines for easier viewing. The wind barbs on the right-hand side of the diagram represent the winds at various elevations, with the top of the diagram representing north. The winds at mandatory levels are plotted at their pressure levels, whereas the winds at height levels are plotted at their standard atmosphere pressure level.

Emagram: An emagram is very close to a skewT except the temperature lines are vertical, not skewed to the right.  It is also an energy conserving diagram.

Stuve: In the Stuve diagram format, the diagram is much the same as the Skew T plot except that the temperature lines are vertical. Pressure lines are spaced so that potential temperature lines are straight. This is not an energy conserving diagram.

Wind plot: The winds at selected levels are plotted on the right side of the diagram. Standard directions are used with up being north and right being to the east.  These are plotted in white but can be changed with the color_wind resource.

Data plot: The geopotential heights are plotted at a 50 mb interval on the left side of the plot. The color of the data can be changed with the color_wind resource. On the right side of the plot, specific parameters and indices are plotted. These values are:

Station information:

WMO WMO number
LAT Latitude of station
LON Longitude of station
EL Elevation of station in meters

Key information:

TP Tropopause level (mb)
MW Max wind level (mb)
FRZ Lowest freezing level (mb) or BG for below ground
WB0 Wet bulb zero (mb) or BG
PW Precipitable water (in)
RH Mean RH surface to 500 mb (%)
MAXT Estimated max temperature (C) using a 150mb layer
TH 1000-500mb thickness (m)
L57 700-500mb lapse rate (C/km)
LCL Lift condensation level (mb) from surface data
LI Lifted index (C) using 100 mean layer above surface
SI Showalter index (C)
TT Total totals index
KI K index
SW Sweat index
EI Energy index

This is a parcel trajectory (the yellow line on the sounding) based on 100 mb mean layer.

CAPE Convective available potential energy
CINH Convective inhibition (open ended)
LCL Lift condensation level (mb)
CAP Cap strength (C)
LFC Level free convection (mb)
EL Equilibrium level (mb)
MPL Maximum parcel level (mb)

Wind parameters

STM Estimated storm motion (knts) from 0-6000m AG mean layer, spd 75% of mean, dir 30 deg veer from mean.
HEL Storm relative helicity 0-3000m AG (total value)
SHR+ Positive shear magnitude 0-3000m AG (sum of veering shear values)
SRDS Storm relative directional shear 0-3000m AG (directional difference of storm relative winds)
EHI Energy helicity index (prop to positive helicity * CAPE)
BRN Bulk Richardson number 500-6000m AG (prop to CAPE/bulk shear)
BSHR Bulk shear value (magnitude of shear over layer)

The amount of data plotted can be regulated by using the data plot parameters:

  • nodata -- no data plotted
  • data -- all data plotted
  • data1 -- minimal data plotted
  • data2 -- important data plotted

Parcel Trajectory: A parcel trajectory is plotted with each sounding as a thick yellow line.  If no parcel trajectory is needed, specifying the noparcel plot parameter will eliminate it from the plot. The type of parcel can changed by specifying the par plot parameter.

Wind hodograph: The wind hodograph is a polar plot of wind speed and direction. The radius directly reflects wind speed. The hodograph is plotted for all mandatory and wind at height levels with the plot annotated with plus signs at each level and labeled with the mandatory level pressures above and to the right of the plus sign. The lowest level data (below 700 mb) is plotted in white.

The plot type can be changed. If the thermodynamic diagram is visible, the hodograph can be plotted by hitting <Meta>n. By hitting <Meta>n again, the thermodynamic plot will reappear.

Sounding Modification

Once the data are plotted, the sounding can be modified. This can be done by moving the cursor to the line which is to be modified, holding down the <Shift-right button> and moving the cursor to where the new value will be.  If the cursor is right of the temperature line, the temperature sounding is modified. If the cursor is left of the dewpoint line, the dewpoint is modified. This can only be done on the existing levels. This can also be done on the hodograph.

In many cases, the sounding has too much detail to effectively select a level or data point.  It is recommended that the user zoom the plot by using the <Shift-left button> and dragging a box around the area to be zoomed. Remember to start at a corner.

Once the sounding is modified, the plotted data/parameters/indices will update to reflect the changed sounding.  The parcel will not automatically update.  This can be done with the <Meta>r refresh command. The modified sounding can be saved to a raw file using the <Meta>s save command. This can be read in by uacalplt to be replotted.

Output Files

By default, this program does not produce output files.  A raw file can be generated using the <Meta>s command in the plot window.  The out_file resource specifies a filename, a file tag (lookup in file name convention file) or a name convention (with wildcards). The output can be GIF file by specifying gif as the file type. It may be desirable to turn plotting of when producing output files. To do this, specify none for the plot_type resource.


   uacalplt -cu=la -id=ILX -pl=skewt -de=d

This plots a skewT diagram for ILX.


  • upa.cty - the surface station location database file


  • uacvt - the upper air decoding program

For further information about WXP, email technical-support@weather.unisys.com
Last updated by Dan Vietor on Sept 29, 1997