sdfopen /grove3/iesuw/ccm1/CCM1-21KEXP-SEAE2025.nc
sdfopen /grove3/iesuw/ccm1/CCM1-CNTROLPI-SEAE2025.nc

*these plots maintain aspect/ratio

*want Altantic ocean in center of plot
set lon -180 180

*define variable we will be plotting
*in file, precip minus evap (pme) is 'p-e' and grads cannot read variable names with '-' in them
*so we must define pme ourselves
*set t to all times so that pme will be define for all time periods
*if we set t=1, pme will just be calculated for DJF

set t 1 5

*.1 and .2 tell what file the variable comes from
*since we opened the 21K file first, that is file 1 (prectmm.1)
*and the ctl file is file 2 (prectmm.2)
*you can use mathematical expressions in grads, as below

define pme21 = prectmm.1 - qflr.1/2.5105e9 * 86400000
define pmectl = prectmm.2 - qflr.2/2.5105e9 * 86400000  


*enable output file
enable print three_panel.prt

*turn grads grid off
set grid off

*set map line attributes: color, style, thickness
*we have increased map line thickness here (6)
set map 1 1 6

*set time to first in file (in this case, DJF)
set t 1

*draw strings on page to label plots
*draw string xpos ypos string
draw string 7.5 8.5 EXP 
draw string 7.5 5.5 CTL 
draw string 7.5 2 DELTA 

*set dimensions on page of first map
*top center of page
*set vpage xmin xmax ymin ymax
set vpage 0 8.5 6.5 11

*turn grads label off (must do this before every plot is drawn)
set grads off

*set explicit contour levels
set clevs -16 -8 -4 -2 -1 0 1 2 4 8 16

*set thickness of contour lines
set cthick 1

*turn off x axis labeling
set xlab %

*draw variable we defined earlier
d pme21 

*draw title
*putting in back slash makes text after the slash go onto a new line
draw title 21KEXP-CNTROLPI  P-E \ DJF 

*second plot
*must reset vpage
set vpage 0 8.5 3.25 7.75
set grads off
set clevs -16 -8 -4 -2 -1 0 1 2 4 8 16
set cthick 1
set xlab %
d pmectl 
print

*third plot
set vpage 0 8.5 0 4.5
set grads off
set clevs -16 -8 -4 -2 -1 0 1 2 4 8 16
set cthick 1

*draw delta of two files
d pme21-pmectl 

*print contour label at bottom
*could also use 'draw string' for this, but
*draw xlab gives nice big type and centers at bottom of plot
draw xlab ci +/- 0 1 2 4 8 16

print
disable print