Re: regridding from WRF to WRF (one grid to another?)

Hi Kelly,

As suggested by Nicole, I'd suggest that you use the new
ESMF regrid functions. These are very high quality. Further,
the ESMF regrid offer 3 different methods for interpolation.

Most commonly, the bilinear or conservative methods are used.
You are going from a 'coarse' resolution (81km) to a fine
resolution (27km), In this case the bilinear method is adequate.
If you were interpolating from fine-to-coarse, I'd suggest
using the conservative method for variable like RAIN* due to
the 'fractal' nature of precipitation.

--
See the Climate Data Guide:
      http://climatedataguide.ucar.edu/
for general comments about interpolation.
      Click: Processing and, then, click Regridding
Good luck
On 09/19/2012 01:10 PM, Schiffer, Nicole June wrote:
> Kelly-
>
> I just did something similar using the new ESMF_regrid in version
> 6.1.0-beta. In my case, I regridded the topography from a 25km run to a
> 10km grid. I've attached my code for reference.
>
> -Nicole
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> *     Nicole Schiffer
> *     Science Writing Intern (NCSA)
> *     Graduate Research Fellow (Dept. of Energy)
> *     Department of Atmospheric Sciences
> *     University of Illinois, Urbana-Champaign
> *     Email: nschiff2 [at] illinois [dot] edu
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
>
>
> "Kelly Mahoney", 9/19/12 1:56 PM:
>
>> Hi,
>>
>> I am trying to interpolate one curvilinear (WRF) grid to another
>> curvilinear (WRF) grid (each with different grid spacing, dimensions,
>> etc.), but just realized that all of the NCL functions listed for
>> regridding curvilinear grids (e.g., rgrid2rcm, rcm2rgrid, rcm2points)
>> are designed to go to/from another (one-dimensional) type of grid.
>>
>> Am I missing a more basic way to do this?
>>
>> I realize that I can also interpolate them both to a standard grid and
>> compare them from there, but optimally I'd have one on the other.
>>
>> Thanks for any suggestions or info anyone might have!
>>
>> Kelly
>>
>> **************************************************************************
>> *********
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"
>>
>> ; Open two files
>>     a = addfile("81km_wrfout_d01_2010-01-22_18:00:00.nc","r")
>>     b = addfile("27km_wrfout_d01_2010-01-22_18:00:00.nc","r")
>>
>> ;km Read in rainc and rainnc, combine
>>     rainnc_a = a->RAINNC(:,:,:)
>>     rainnc_b = b->RAINNC(:,:,:)
>>
>>     rainc_a = a->RAINC(:,:,:)
>>     rainc_b = b->RAINC(:,:,:)
>>
>>     prec_a = rainc_a(:,:,:)+rainnc_a(:,:,:)
>>     prec_b = rainc_b(:,:,:)+rainnc_b(:,:,:)
>>
>> ;km get lat of 81km grid
>>      lat_a = a->XLAT(0,:,:)
>>      lon_a = a->XLONG(0,:,:)
>>
>> ;km get lat of 27km grid
>>      lat_b = b->XLAT(0,:,:)
>>      lon_b = b->XLONG(0,:,:)
>>
>>     prec_b_interp = rcm2rgrid_Wrap(lat_b,lon_b,prec_b,lat_a,lon_a,0)
>> ;km  27km onto 81kmgrid
>>
>>     prec_diff = prec_a - prec_b_interp
>>
>>     printVarSummary(prec_diff)
>>
>> end
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>
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