[gradsusr] Plot a symbol on map where difference field exceeds a threshold

Tracey tdorian10 at gmail.com
Thu Dec 13 13:53:00 EST 2018

Hi GrADS users,

I was wondering if anyone knew if there was a way to plot a large enough
symbol on a global map in GrADS where a difference field exceeds a specific

For example, in my GrADS script I am plotting sea surface temperatures and
masking out land areas:

'set_parea 2 2 2 1 -margin 'margin
*'color -levs -15 -10 -5 5 10 15 -kind blue->white->red'
*'color -20 20 5 -kind blue->white-(0)->white->red'*
*'d (TMPsfc.2-TMPsfc.1)'*
'q gxinfo'
say '    (x1,x2) = ('x1','x2')'
say '    (y1,y2) = ('y1','y2')'
'xcbar 'x1' 'x2' 'y1-0.3' 'y1-0.2' -fw .06 -fh .06 -fs 1'
'draw title FV3-GFS'
* 'set rgb 73 80 80 80'
'set rgb 73 255 255 255'
** Plots ocean temperatures and masks land **
'basemap L 73 1 M'
** Plots land temperatures and masks ocean **
*'basemap O 0 1 H'

I want to say in GrADS, look at all points on the global map (not including
land) and plot a large enough star that the user can see anywhere in the
globe where the difference in surface temperature exceeds 10 degrees
Celsius, for example.  Does anyone know how I can do this?

Thank you,
Tracey Dorian
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