SNCROSS draws cross sections through sounding data.

INPUT PARAMETERS
 
    CXSTNS    *Cross-section station line
    SNPARM    *Sounding parameter list
    SNFILE    *Sounding data file
    DATTIM    *Date/time
    VCOORD    *Vertical coordinate type
    PTYPE     *Plot type/h:w ratio/margins
    YAXIS     *Ystrt/ystop/yinc/lbl;gln;tck
    TAXIS     *Time1-time2-tinc;lbl;gln;tck
    LINE      *Line color/type/width/label
    BORDER    *Background color/dash/width
    CINT      *Contour interval/min/max
    WIND      *Wind symbol/siz/wdth/typ/hdsz
    TITLE     *Title color/line/title
    PANEL     *Panel location/color/dash/width
    DEVICE    *Graphics device
    CLEAR     *Clear screen flag
    FILTER    *Filter data factor
    TEXT      *Text size/font/width/hw flag
    CURVE     *Curve fit type
    CONTUR    *Contour attributes
    FINT      *Fill interval/min/max
    FLINE     *Fill colors
    CTYPE     *Contour type:  C/F
 
 

PROGRAM DESCRIPTION
 
    SNCROSS draws cross sections using upper-air sounding data.
    The cross-section line, CXSTNS, must be specified as a list
    of stations separated with semicolons.  Alternatively, a
    single station may be entered in CXSTNS and a list of times
    in DATTIM.  In this case, a time section will be drawn.

    Any parameter that can be computed from the data set
    parameters can be displayed.  The parameter to be displayed
    is specified in SNPARM.  If the value of SNPARM is ISEN,
    isentropes will be drawn.  Note that SNPARM may also be
    THTA, in which case, potential temperature will be gridded
    and contoured.  ISEN will fit splines to the station data
    in plot space and then check for tangled lines and untangle
    them if necessary.  When SNPARM = ISEN, the results should
    be the same as in the GEMPAK4 version of SNCROSS.

    Contours may be displayed as lines or as a color fill.
    CTYPE must be set to C for lines.  If CTYPE = F, a color
    fill is produced.  If CTYPE = F/L, the color fill is
    produced and labelled contour lines are drawn using the
    input for CINT and LINE.  Filling is not available when
    SNPARM = ISEN.

    The attributes of the contour lines, including the color,
    line type, line width, and label frequency are specified
    in LINE.  The four attributes are separated with slashes;
    semicolons separate the values for each attribute.  If the
    line type is set to a single negative number, negative
    contour values will have the absolute value of the line type
    and positive values will be solid.  If the label type is set
    to a single number, n, then every nth value will be labeled.

    The attributes of the color fill are specified in FLINE.
    FINT specifies the interval or levels for the color fill.
    The first color specified in FLINE fills values less than the
    first level; while the last color fills values greater than
    the last level.  Hence, n levels requires n+1 colors.

    The plot background consists of a pressure axis, a horizontal
    axis with the station names, a hatched region indicating the
    part of the plot below the earth surface, and vertical lines
    at each station.  The station lines are solid up to the level
    at which wind data stop, and are dashed from there to the
    level at which temperature data stop.  The color for the entire
    background is given in BORDER.

    The horizontal axis represents a straight line between the
    first and last stations.  The positions of intervening stations
    are proportional to the perpendicular projections of the actual
    positions onto the section line.  All of these calculations
    are done in lat/lon coordinates.  If the plot is a time section,
    the times will be displayed on the x axis with the earliest
    time at the left.  If the first character in TAXIS is an R, the
    earliest time will appear on the right.

    The vertical coordinate may be specified as LIN, LOG, or STUVE;
    SKEWT is not valid in this program.  The bottom and top limits
    for the y axis are specified in YAXIS, but the axis labelling
    specifications are ignored.


EXAMPLES
 
     1.  Draw isentropes in color 5, line type 2, labelling
         every line.  Plot the background in color 1.  Use a
         logarithmic scale for the y axis and a 4 Kelvin
         interval for the isentropes.  Draw wind barbs in color
         number 2 at the stations.

         CXSTNS  =  sep;ggg;jan;ckl;ahn;chs
         SNPARM  =  isen
         SNFILE  =  sound.snd
         DATTIM  =  last
         VCOORD  =  pres
         PTYPE   =  log
         YAXIS   =
         TAXIS   =
         LINE    =  5/2/1
         BORDER  =  1
         CINT    =  4
         WIND    =  bm2
         TITLE   =
         PANEL   =  0
         DEVICE  =  xw
         CLEAR   =  yes
         FILTER  =  yes
         CURVE   =  2
         TEXT    =

     2.  Draw a time section using all the data in the file for
         IAD.

         CXSTNS  =  iad
         DATTIM  =  all

ERROR MESSAGES
 
    [SNCROSS  -1]   Fatal error initializing TAE.
    [SNCROSS  -2]   Fatal error reading TAE parameters.
    [SNCROSS  -3]   GEMPLT initialization error.
    [SNCROSS  -4]   Vertical coordinate for isentropes must be PRES.
    [SNCROSS  -5]   There are no times in the file.
    [SNCROSS  -6]   Fewer than four stations/times were selected.
    [SNCROSS  -7]   Data buffer is too small.
    [SNCROSS  -8]   Temperature or pressure data not available.
    [SNCROSS  -9]   The station ... cannot be found in the data set.
    [SNCROSS -10]   Error setting up graph; check invalid LOG axis.
    [SNCROSS -11]   Input ... for PTYPE is invalid.
    [SNCROSS -12]   Either input ... for YAXIS or input for VCOORD is invalid.
    [SNCROSS -13]   Parameter ... is not computable.
    [SNCROSS -14]   Parameter ... is a character.
    [SNCROSS -15]   The grid coordinates cannot be defined.
    [SNCROSS -16]   Multiple station entry is invalid for time sections.
    [SNCROSS -17]   Data at time ... is not in the file.
    [SNCROSS -18]   Wind data cannot be computed.