Ascending order of latitude when applying function such as "uv2dv_cfd" ?

Hi, all

      Recently I applied a function of "uv2dv_cfd" to calculate the divergence using 850hpa wind of Ncep analysis.

As to the introduction of the function (http://www.ncl.ucar.edu/Document/Functions/Built-in/uv2dv_cfd.shtml),

the latitude dimension of u and v should be in ascending order. When I print the latitude I found that it starts from 90 to -90.

however, the function work well and did not report any error when I apply it to the variable directly without reordering .

( the codes is : dv = uv2dv_cfd (u, v,u&lat,u&lon, 0) )

       Besides, I also search a similar case as below http://www.ncl.ucar.edu/Support/talk_archives/2009/2408.html

I revised my codes according to the above case,

    ( the codes is

   ux = u(:,::-1,:) ; The latitude dimension must be in ascending order when applying the function of us2dv_cfd
   vx = v(:,::-1,:)
   dv = uv2dv_cfd (ux,vx, ux&lat,ux&lon, 0) )

    and this time I got the same result .

      I am a little puzzled. Anyone can show me a hand? Thanks!

lin

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Received on Tue May 7 09:42:52 2013