[gradsusr] Horizontal Temperature Gradient

[Ricardo Hallak]

Hy, Mano. Follow the instructions below, from the GrADS homepage. It will
fix your mistake.
*cdiff*

cdiff(*expr,dim*)

Performs a centered difference operation on *expr* in the direction
specified by *dim*. The difference is done in the grid space, and no
adjustment is performed for unequally spaced grids. The result value at
each grid point is the value at the grid point plus one minus the value at
the grid point minus one. The *dim* argument specifies the dimension over
which the difference is to be taken, and is a single character: X, Y, Z, or
T.

Result values at the grid boundaries are set to missing.

Usage Notes

Examples


   1. The cdiff function may be used to duplicate the calculation done by
   the hcurl <http://cola.gmu.edu/grads/gadoc/gradfunchcurl.html> function:

   define dv = cdiff(v,x)define dx = cdiff(lon,x)*3.1416/180define du =
   cdiff(u*cos(lat*3.1416/180),y)define dy = cdiff(lat,y)*3.1416/180display
   (dv/dx-du/dy)/(6.37e6*cos(lat*3.1416/180))

   The above example assumes an X-Y varying dimension environment. Note
   that the intrinsic variables lat and lon give results in degrees and
   must be converted to radians in the calaculation. Also note the radius of
   the earth is assumed to be 6.37e6 meters thus the U and V winds are
   assumed to have units of m/sec.

   2. Temperature advection can be calculated using the cdiff function as
   follows:

   define dtx = cdiff(t,x)define dty = cdiff(t,y)define dx =
   cdiff(lon,x)*3.1416/180define dy = cdiff(lat,y)*3.1416/180display -1*(
   (u*dtx)/(cos(lat*3.1416/180)*dx) + v*dty/dy )/6.37e6

   where the variable t is temperature, u is the U component of the wind,
   and v is the V component of the wind.

-- 
Prof. Ricardo Hallak
Laboratório de Meteorologia de Mesoescala - LMM
Departamento de Ciências Atmosféricas
Instituto de Astronomia, Geofísica e Ciências Atmosféricas
Universidade de São Paulo

Phone: +55(11)3091-4698


Em ter., 16 de jun. de 2020 às 23:25, lpasmanoranjan <
lpasmanoranjan at gmail.com> escreveu:

> Dear Users,
> I would like to calculate horizontal temperature gradient. The following
> script plots strange values. Perhaps I am making some mistake, would anyone
> please check the script.
>
> dtx = cdiff(t,x)
> dx = cdiff(lon,x)*3.1416*6.37e6*cos(lat*3.1416)
> d dtx/dx
>
> Thank you.
> --
> Kind Regards,
> Mano
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://gradsusr.org/pipermail/gradsusr/attachments/20200617/27be4966/attachment.html>