Re: divergence functions

Yes, I now see why uv2dvF and the center_finite_diff_n would give me wrong
answers. Thank you for the reply Sir.

On Tue, Jan 29, 2013 at 6:47 PM, Dennis Shea <shea@ucar.edu> wrote:

>
> 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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>>
>

-- 
Fiaz Ahmed
Graduate Research Assistant
Department of Atmospheric Sciences
Texas A&M University
fiaz.500@tamu.edu

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Received on Wed Jan 30 09:33:15 2013