Re: Petterssen frontogenesis

Forgot to mention ....

If you do use the spherical harmonic functions, they do
require that the grids be ordered south->north.

Likely, the GFS are N->S. Use NCL syntax to reorder

if x(time,lev,lat,lon)

    x = x(:,:,::-1,:)

if x(time,lat,lon)

    x = x(:,::-1,:)

    printVarSummary(x)

On 12/10/12 8:56 AM, Dennis Shea wrote:
> There is no builtin Petterssen frontogenesis equation.
>
> However, the GFS is a global grid and the spherical harmonic
> functions could be used to accurately calculate some of the
> various terms.
>
> gradient terms: du/dx, dv/dx, dy/dy, du/dy
> http://www.ncl.ucar.edu/Document/Functions/Built-in/gradsf.shtml
>
> There is an **unsupported** function in shea_util.ncl
>
> function advect_gradient (u:numeric, v:numeric, x:numeric \
> ,gridType[1]:integer, con[1]:numeric \
> ,long_name:string, units:string, iopt[1]:integer)
> ;
> ; linear advection of a scalar quantity: UV.GRADIENT(X)
> ; : U*(dX/dlon) + V*(dX/dlat)
> ======
> The documentation is embedded in the library. You can read vis:
>
> %> less $NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl
>
> search for 'advect_gradient'
>
> Don't know about the calculation of the angles.
>
>
> On 12/9/12 3:56 AM, Adrian Antonescu wrote:
>> Hi,
>>
>> Does anyone have a NCL script to calculate Petterssen frontogenesis?
>> I am trying to calculate Petterssen frontogenesis using the GFS 0.5
>> degrees data.
>>
>> Thank you so much.
>>
>> Bogdan Antonescu
>>
>> The University of Manchester
>> Simon Building, Oxford Road
>> Manchester, M13 9PL, United Kingdom
>> Room 3.16, Simon Building
>> +44 (0)161 306 3911
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Received on Tue Dec 11 02:34:28 2012