Re: divergence functions

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Tue Jan 29 2013 - 17:47:47 MST

   1) div=uv2dvF(u,v)
is not appropriate. As noted in the documentation,
the uv2dvF function *requires* the input to be global.
Your data is not global. Hence, erroneous results!

   2) div1=uv2dv_cfd(u,v,lat,lon,2)

As noted in the documentation, this function uses
     dv = Dv/Dy + Du/Dx -(v/a)*tan(phi)

     dv(j,i) = (v(j+1,i)-v(j-1,i))/dy2(j)
               + (u(j,i+1)-u(j,i-1))/dx2(j)
               - (v(j,i)/a)*tan(phi(j))

On 01/29/2013 04:26 PM, Fiaz Ahmed wrote:
> I have horizontal wind fields u(time,level,lat,lon) and v on a fixed
> grid. (15S to 15N ; 40E to 160E). I computed the horizontal wind
> divergence using the following three functions:
>
> 1) div=uv2dvF(u,v)
> 2) div1=uv2dv_cfd(u,v,lat,lon,2)
> 3) div2=
> center_finite_diff_n(u,lon,False,0,3)+center_finite_diff_n(v,lat,False,0,2)
>
> Is there any reason why, the above values would not be approximately
> equal? My divergence values differ from each other by at least one order
> of magnitude.
>
> --
> Fiaz Ahmed
> Graduate Research Assistant
> Department of Atmospheric Sciences
> Texas A&M University
>
> <mailto:fiaz.500@tamu.edu>
>
>
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Received on Tue Jan 29 17:47:56 2013

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