[gradsusr] Advection term in the moisture convergence equation

[Lyndon Mark Olaguera]

Dear All,

I'm trying to calculate the moisture flux convergence using the following
commands:

*At 850 mb

'set dfile 1'
'define q=shum(z=3)'

'set dfile 2'
'define u=uwnd(z=3)'

'set dfile 3'
'define v=vwnd(z=3)'

'color -0.2 0.2 0.02 -kind blue->white->red'
'define mconv=(1)*hdivg(u*q,v*q)*1e6'

According to this link, I have to add the advection term.

http://www.spc.noaa.gov/publications/banacos/mfc-sls.pdf

[image: Inline image 1]

Question:

1. Is there a way to do this in grads?
2. Or is there a function in GRADS that can calculate partial derivatives?

I'll appreciate any help.

Best,

*Lyndon Mark P. Olaguera*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20170128/a8cb8af3/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 11693 bytes
Desc: not available
Url : http://gradsusr.org/pipermail/gradsusr/attachments/20170128/a8cb8af3/attachment-0002.png 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screenshot from 2017-01-28 14-31-32.png
Type: image/png
Size: 13875 bytes
Desc: not available
Url : http://gradsusr.org/pipermail/gradsusr/attachments/20170128/a8cb8af3/attachment-0003.png