[ncl-talk] Derivatives in NCL
Dennis Shea
shea at ucar.edu
Mon Feb 6 10:59:03 MST 2017
The is no need for a function. Re is a scalar
f = addfile("foo.grb","r")
h = f->GEOHGT ;[lv_ISBL0 | 37] x [ygrid_0 | 113] x [xgrid_0 | 151]
Re = 6356766.0
Z = (h*Re)/(Re-h)
; assign appropriate attributes
Z at long_name = "Geometric Height"
Z at units = "m"
; copy selected attributes
Z at coordinates = "gridlat_0 gridlon_0"
Z at forecast_time = h at forecast_time
Z at forecast_time_units = h at forecast_time_units
Z at initial_time = h at initial_time
; copy any coordinate variables
copy_VarCoords(h,Z)
printVarSummary(Z)
=============================
You may wish to create your own function
undef("geometric_height")
function geometric_height(h:numeric)
local Re, Z
begin
Re = 6356766.0
Z = (h*Re)/(Re-h)
; assign appropriate attributes
Z at long_name = "Geometric Height"
Z at units = "m"
; copy selected attributes
Z at coordinates = "gridlat_0 gridlon_0"
Z at forecast_time = h at forecast_time
Z at forecast_time_units = h at forecast_time_units
Z at initial_time = h at initial_time
; copy any coordinate variables
copy_VarCoords(h,Z)
return(Z)
end
=============
As an experiment, add
*setfileoption*("grb","SingleElementDimensions","Initial_time")
before
f = addfile("foo.grb","r")
h = f->GEOHGT
print(h)
===============
If you are new to NCL, please see the DKRXZ tutorials at:
https://www.ncl.ucar.edu/Document/Manuals/
On Mon, Feb 6, 2017 at 9:04 AM, Black, Forrest (LARC-D318)[UNIVERSITIES
SPACE RESEARCH ASSOCIATION] <forrest.black at nasa.gov> wrote:
> Hello all,
>
>
>
> I am trying to solve the following equation in NCL:
>
>
>
> Z = (h*Re)/(Re-h)’
>
>
>
> Z: Geometric Height
>
> h: Geopotential height (3D Array)
>
> Re: Radius of Earth, assumed constant (6356766m)
>
>
>
> I have looked at some old threads, but am still unsure of what functions I
> would use to calculate (Re-h)’.
>
>
>
> Can anyone give me some suggestions on how to tackle this?
>
>
>
> This is the Attribute data for Geopotential Height:
>
>
>
> Variable: Geopotential Height
>
> Type: float
>
> Total Size: 2525324 bytes
>
> 631331 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [lv_ISBL0 | 37] x [ygrid_0 | 113] x [xgrid_0 | 151]
>
> Coordinates:
>
> lv_ISBL0: [10000..100000]
>
> Number Of Attributes: 13
>
> center : US National Weather Service - NCEP (WMC)
>
> production_status : Operational products
>
> long_name : Geopotential height
>
> units : gpm
>
> _FillValue : 1e+20
>
> coordinates : gridlat_0 gridlon_0
>
> grid_type : Lambert Conformal can be secant or tangent, conical or
> bipolar
>
> parameter_discipline_and_category : Meteorological products, Mass
>
> parameter_template_discipline_category_number : ( 0, 0, 3, 5 )
>
> level_type : Isobaric surface (Pa)
>
> forecast_time : 0
>
> forecast_time_units : hours
>
> initial_time : 01/31/2017 (00:00)
>
>
>
>
>
> Thanks for any help.
>
>
>
> - Forrest
>
>
>
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