# Moisture flux convergence in GrADS

I want to calculate vertically integrated moisture flux convergence (VIMFC) in GrADS.

But when I give the following instruction it marks me errors:

sdfopen shum.mon.mean.nc
sdfopen uwind.mon.mean.nc
sdfopen vwind.mon.mean.nc

set lon 180 320
set lat 0 60
set t 763 766
set lev 1000 300

qu=vint(1000,shu,.1*uwnd.2,300)
qv=vint(1000,shu,.1*vwnd.3,300)

vimf=-hdivg(qu,qv)
d vimf

ga-> qu=vint(1000, shum.1*uwnd.2,600)


Error from VINT:

Incompatible grids.
*** glibc detected *** grads: double free or corruption (!prev): 0x0000000003707c40 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.

6(+0x7e846)[0x7f898ac4c846]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7f898abef76d]
======= Memory map: ========
00400000-00bcb000 r-xp 00000000 08:05 1573111
7f898bdc2000-7f898bdc3000 r--p 00017000 08:05 1572886                    /lib/x86_64-linux-gnu/libpthread-2.15.soAborted (core dumped)


Does anyone know how to fix it?

Best, Pablo Camarena

• have you checked the grids of your input files to see if they match? It does say "Incompatible grids."
– f.thorpe
May 31 '17 at 3:01
• That'd be my first guess too. I remember GrADS being annoyingly uninformative during errors like yours May 31 '17 at 6:02
• I have come across the same problem. Some time ago, I have started using Matlab and R. Things have become more transparent. For some starting reference, I suggest taking a look at this topic: earthscience.stackexchange.com/a/10667/8396 Jun 28 '17 at 13:53