[gradsusr] Plotting EP Fluxes in GrADS

[Jason Furtado]

All -

I am running into an issue with plotting EP flux vectors on the 
latitude-by-pressure plane in GrADS.  I did the calculations in another 
language and wrote out relevant data (EPy, EPz, and the divergence of 
the flux) to a binary file to load and plot in GrADS.   I have checked 
my plot against a plot that I can generate on the NCEP website and the 
vertical direction of the arrows is reversed (they point down in the 
GrADS plot but should point up according to the NCEP plot).

Having checked the values plotted in GrADS (using gxout grid), many of 
the values of EPz are negative.  According to the Edmon et al. (1980) 
paper, in pressure coordinates, positive (negative) EPz should point 
toward higher (lower) pressure.  Is this an issue with GrADs?  Anyone 
else run into this issue?  My (abbreviated) script is below.

reinit
set background 1

open epfluxes_epdiv_2009_2010_obs.ctl

set t 390 390
set lat 10 90
set vpage 0 11 0 6
set annot 0

set gxout vector
set zlog on
set z 1 17
set xaxis 10 90 10
set xlabs 10N|20N|30N|40N|50N|60N|70N|80N|90N|
set ylevs 10 50 100 300 500 1000
set grads off
set grid off
set font 1
set ylopts 0 4 0.2
set xlopts 0 4 0.2

set arrscl 1 200
set ccolor 2
set cthick 6
set arrowhead -0.25
set arrlab on
set grid off
d skip(epy,2,1);skip(epz,2,1)

Thanks!
- Jason
-- 
Jason C. Furtado, Ph.D.
Staff Scientist
Atmospheric and Environmental Research (AER), a Verisk Analytics company
131 Hartwell Ave.
Lexington, MA 02421