GDCROSS displays a vertical cross section of scalar and/or vector grids. INPUT PARAMETERS CXSTNS *Cross-section station line GDATTIM *Grid date/time GVCORD *Grid vertical coordinate GFUNC *Grid function GVECT *Grid vector function GDFILE *Grid file WIND *Wind symbol/siz/wdth/typ/hdsz PTYPE *Plot type/h:w ratio/margins YAXIS *Ystrt/ystop/yinc/lbl;gln;tck CINT *Contour interval/min/max SCALE *Scaling factor LINE *Line color/type/width/label BORDER *Background color/dash/width TITLE *Title color/line/title CLEAR *Clear screen flag DEVICE *Graphics device TEXT *Text size/font/width/hw flag PANEL *Panel location/color/dash/width CONTUR *Contour attributes FINT *Fill interval/min/max FLINE *Fill colors CTYPE *Contour type: C/F PROGRAM DESCRIPTION GDCROSS draws a vertical cross section between two points in a grid field. The cross-section path is a line segment on the grid projection plane joining the two points. Gridded data are interpolated to the cross-section plane at intervals corresponding to approximately one grid increment. CXSTNS specifies the beginning and ending points of the cross section. Each point may be entered as a latitude and longitude separated by a semicolon, as station identifiers or numbers or as x and y grid coordinates separated by a semicolon and preceded by @. The two points are separated by >. The vertical coordinate, set in GVCORD, can be PRES, THTA, or HGHT. The data must be stored in that vertical coordinate in the grid file. No automatic vertical interpolation is included. The vertical axis scaling, set in PTYPE, can be LIN, LOG, KAP or STUVE. STUVE and KAP are the same; SKEWT may not be entered. The plot aspect ratio and margins may also be entered in PTYPE. Both scalar and vector fields can be displayed in the cross-section plane. Contour lines are drawn through the scalar field. Vector fields may be depicted using arrows or barbs. If M is entered in WIND, winds will be displayed in meters per second unless the KNOTV operator has been specified in GVECT, in which case the winds will be displayed in knots. IF K is entered in WIND, the wind is displayed in knots. The line contours and filled contours are specified as in GDCNTR. Circulations can be displayed in the cross-section plane by specifying GFUNC = CIRC ( V, W ), where V is a vector field and W is the scalar vertical motion in the GVCORD coordinate. The horizontal component of the circulation is the tangential component of V. The vertical component is W scaled up to account for the exaggerated aspect ratio of the display relative to that of the real atmosphere. For the CIRC operator, W is assumed to be pressure velocity in mb/s for PRES and THTA coordinates and cm/s for the HGHT coordinate. If the vertical component does not require scaling, the circulation can be specified explicitly in the form GVECT = VECR ( TANG ( V ), W )/VERT, where VERT is a flag indicating that the vector components should not be rotated to be north-relative. EXAMPLES 1. Plot temperature in Celsius on a log-P chart along the cross section from BWI to LAX. Plot the contours in color number 2, using thick, solid lines. Plot wind barbs for the wind. Plot the chart to 50 millibars using the default labels. Accept default values for the other parameters. CXSTNS = bwi>lax GDATTIM = last GVCORD = pres GFUNC = tmpc GVECT = wnd WIND = bm1 GDFILE = ngm.grd PTYPE = log YAXIS = /50 CINT = SCALE = LINE = 2/1/7 BORDER = TITLE = CLEAR = yes DEVICE = ps TEXT = PANEL = CTYPE = l 2. Now, using the same file, plot a log pressure cross section of the vorticity advection, scaled by 10**9. Also, plot the ageostrophic circulation using arrows. Use a cross-section line from grid point (1,1) to grid point (10,20). Use a height-to-width plot ratio of 2. CXSTNS = @1;1>@10;20 GFUNC = adv ( avor ( wnd ); wnd ) GVECT = circ ( age; omeg ) PTYPE = log/2 SCALE = 9 WIND = am1 ERROR MESSAGES [GDCROSS +2] Surface value of GVCORD is not available. [GDCROSS +1] WARNING. There are no contour levels. [GDCROSS -1] Fatal error initializing TAE. [GDCROSS -2] Fatal error reading TAE parameters. [GDCROSS -3] Fatal error initializing GEMPLT. [GDCROSS -4] Input for CXSTNS is invalid. [GDCROSS -5] Input for GDATTIM is invalid. [GDCROSS -6] Input for GVCORD is invalid. [GDCROSS -7] Input for PTYPE is invalid. [GDCROSS -8] Graph coordinates are incorrectly defined. [GDCROSS -9] No points found for cross section. [GDCROSS -10] LOG is not possible for this vertical coordinate. [GDCROSS -11] Cross-section coordinates are invalid. [GDCROSS -12] No levels--check input for GDATTIM and GVCORD. [GDCROSS -13] @LEVEL in-line parameter is not allowed. [GDCROSS -14] %VCORD in-line parameter is not allowed. [GDCROSS -18] GVECT cannot be evaluated. [GDCROSS -19] GFUNC cannot be evaluated. [GDCROSS -20] Input for YAXIS is invalid.