From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>

Date: Fri Apr 19 2013 - 14:06:43 MDT

Date: Fri Apr 19 2013 - 14:06:43 MDT

My suggestion would be interpolate your WRF grid to a rectilinear grid

via the ESMF regridding:

http://www.ncl.ucar.edu/Applications/ESMF.shtml

See example 5

Then use the center_finite_diff function to compute the quantities.

On 4/19/13 2:14 AM, Bogdan Antonescu wrote:

*> Hi,
*

*>
*

*> Thank you very much for your help. I have managed to calculate
*

*> Petterssen frontogenesis from GFS using "gradsf" and "advect_gradient"
*

*> from shea_util. Now I want to calculate Miller frontogenesis using WRF
*

*> output data. Basically I want to calculate these therms: dtheta/dx,
*

*> dtheta/dy, du/dx, du/dy, dv/dx, dv/dy. I am not sure how to do this, and
*

*> I don't think that I can use the spherical harmonic functions with WRF.
*

*>
*

*> Thank you very much,
*

*> Bogdan
*

*>
*

*>
*

*>
*

*> On 10/12/12 16:43, Dennis Shea wrote:
*

*>> 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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*

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*

*>>>>
*

*>
*

*>
*

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Received on Fri Apr 19 14:06:44 2013

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