Re: regrid Coupled Model Intercomparison Project 3 (CMIP 3) data

[1]
The g2fsh uses spherical harmonics to regrid. This
is adequate for continuous unbounded variables. It is
not appropriate for bounded variables such as precipitation
[lower bound is 0.0] or relative humidity [low bound = 0.0,
high bound=100].

It looks like you are using g2fsh for precipitation. If you
use spherical harmonics, you may get some grid points with
values less than 0.

As noted in documentation, g2fsh includes gridded points at the poles.
If the regridded variable is an appropriate variable, you would have
to use
         newgrid = f2fosh_Wrap( g2fsh_Wrap( orig, (/73,144/) )

[2]
I recommend using linint2_Wrap or area_hi2lores_Warp.

http://www.ncl.ucar.edu/Document/Functions/Contributed/linint2_Wrap.shtml
http://www.ncl.ucar.edu/Document/Functions/Contributed/area_hi2lores_Wrap.shtml

Good luck

Anandhi Aavudai wrote:
> Hi,
>
> I would like to regrid the daily data from the various AOGCMs in Coupled Model Intercomparison Project 3 (CMIP 3) having different gausian grids to a common grid at every 2.5 deg lat & 2.5 deg lon.
>
> My sample program for regriding 1 AOGCM is
>
> begin
> ;=========================================;
> ; step 1: read netcdf file
> ;=========================================;
>
> in= addfile (fili(1), "r")
> orig = in->pr
> time = in->time
> lat = in->lat
> lon = in->lon
> ;=========================================;
> ; interpolate to new grid
> ;=========================================;
> newgrid = g2fsh_Wrap(orig,(/72,144/))
> printVarSummary(newgrid)
> print(lat)
> end
>
> Some questions in this regard
>
> 1. Is "g2fsh_Wrap" the appropriate function for this purpose?
> 2. If answer to question 1 is yes, the numbers 72 & 144 did not give me the regridded values at every 2.5 deg lat & lon (lat = -87.5,-85,....85, 87.5)
> i obtained the numbers : 72 by dividing (all lat) 180 by 2.5;
> 144 by dividing (all lon) 360 by 2.5;
>
>
> printing the summary of newgrid
> printVarSummary(newgrid) gave me these results
>
> Variable: newgrid
> Type: float
> Total Size: 151455744 bytes
> 37863936 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 3652] x [lat | 72] x [lon | 144]
> Coordinates:
> time: [58804.5..62455.5]
> lat: [-90..90]
> lon: [ 0..357.5]
> Number Of Attributes: 7
> long_name : Accumulated Total Precipitation
> original_units : mm/day
> units : kg m-2 s-1
> missing_value : 1e+20
> _FillValue : 1e+20
> cell_methods : time: mean (interval: 30 minutes)
> standard_name : precipitation_flux
> -------printing lat---
> print(lat) gave--
> Variable: lat
> Type: double
> Total Size: 512 bytes
> 64 values
> Number of Dimensions: 1
> Dimensions and sizes: [lat | 64]
> Coordinates:
> lat: [-87.86380004999999..87.86380004999999]
> Number Of Attributes: 5
> long_name : Latitude
> standard_name : latitude
> axis : Y
> units : degrees_north
> bounds : lat_bnds
> (0) -87.86380004999999
> (1) -85.0965271
> (2) -82.31291199
> (3) -79.52560425
> (4) -76.73690033
> (5) -73.9475174
> (6) -71.15775299000001
> (7) -68.36775969999999
>
> 3. why did print(lat) not give fixed grid values at 2.5 degree spacing in latitudes? Are lat array values (printed above) represent the latitude values before the file is regridded?
> 4. how to access the values of 72 latitudes & 144 longitudes of newgrid array?
>
> Thanks in advance for the help.
>
> regards
> anandhi
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Received on Mon Oct 05 2009 - 08:59:56 MDT