# [ncl-talk] Calculation of Horizontal Moisture Flux Convergence

Dennis Shea shea at ucar.edu
Tue Aug 20 21:09:10 MDT 2019

```This '*MFC* question' has been sent to ncl-talk in the past....several
times!
You should look at the archives.One *MFC* answer is here:

*http://mailman.ucar.edu/pipermail/ncl-talk/2014-December/001686.html*
<http://mailman.ucar.edu/pipermail/ncl-talk/2014-December/001686.html>

Extracted from this response, is the expansion of  *DIV*(U*Q) within the
integral into two separate components.

>    *MFC = Moisture Flux Convergence*>>    *MFC_advect** = -( u*(dq/dx)+v*(dq/dy) )    ; advection term
*>    *MFC_conv **  = -q*( (du/dx)+  (dv/dy) )    ; con(div)-vergence
*>>    *MFC = MFC_advect + MFC_conv*

*==========*

I created two examples at:
*https://www.ncl.ucar.edu/Applications/wind.shtml*
<https://www.ncl.ucar.edu/Applications/wind.shtml>

*mfc_div_1.ncl *which implements the *DIV*(*v*q) form
*mfc_div_2.ncl *which implements the components form.

'Luckily', they give the same 'answer'.

Another example of implementing 'vector'/'divergence' operators/functions
is just above these examples. See:: *wind_6.ncl*
=========

I suggest that you and others who are interested in
'budgets'/fluxes/vertical-integration' carefully read Dave Stepaniack's::*
http://www.cgd.ucar.edu/cas/catalog/newbudgets/*
<http://www.cgd.ucar.edu/cas/catalog/newbudgets/>

On Fri, Aug 16, 2019 at 4:48 AM Atul Saini via ncl-talk <ncl-talk at ucar.edu>
wrote:

> Hi NCL-talk,
>                        * Is there any function available in NCL to
> calculate the Horizontal Moisture Flux Convergence?* Please have a look
> at the method provided below and suggest the function in NCL-
>
> [image: image.png]
>
>
>
> Regards,
>
>
>
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