Regridding CAM4 1 degree FV grid to Gaussian

From: Scott Capps <scapps_at_nyahnyahspammersnyahnyah>
Date: Fri Jun 03 2011 - 11:21:28 MDT

Greetings,

I want to regrid CCSM4 (CAM only) output to a Gaussian Grid (for input
to WRF's metgrid.exe) and wanted to make sure I am using the correct NCL
subroutine while preserving the resolution. The regridded output looks
good so, I just need a sanity check. Here is my understanding:

CAM4 was run and output at 1 degree resolution (0.9x1.25, a regular
lon/lat finite volume grid). Here are some of the lat and lon vectors:

Constant longitude grid spacing (1.25 degrees):
lon[0]=0 degrees_east
lon[1]=1.25 degrees_east
lon[2]=2.5 degrees_east
...
lon[285]=356.25 degrees_east
lon[286]=357.5 degrees_east
lon[287]=358.75 degrees_east

Quasi-constant spacing along latitude (varying slightly):

lat[0]=-90 degrees_north
lat[1]=-89.057591623 degrees_north
lat[2]=-88.1151832461 degrees_north
lat[3]=-87.1727748691 degrees_north
lat[4]=-86.2303664921 degrees_north
lat[5]=-85.2879581152 degrees_north
lat[6]=-84.3455497382 degrees_north
lat[7]=-83.4031413613 degrees_north
...
lat[185]=84.3455497382 degrees_north
lat[186]=85.2879581152 degrees_north
lat[187]=86.2303664921 degrees_north
lat[188]=87.1727748691 degrees_north
lat[189]=88.1151832461 degrees_north
lat[190]=89.057591623 degrees_north
lat[191]=90 degrees_north

Here is the script I am using to convert this grid to Gaussian:

begin
;
; Create regular spaced lon vector
nlon = 288 ; 360./1.25 degree
nlon@double = True
glon = lonGlobeF(nlon, "lon", "longitude", "degrees_east")
glon@long_name = "longitude"
glon = decimalPlaces(glon,3,True)
;
; Determine and build Gaussian Grid parameters: Want to preserve
; resolution of orig grid: lon=1.25dgr; lat=0.92dgr
nlat = 196 ; lat spacing ~0.92dgr
nlat@double = True
glat = latGau(nlat, "lat", "latitude", "degrees_north")
glat@long_name = "latitude"
;
; REGRID TO GAUSSIAN GRID:
flat = file1->lat
nflat = dimsizes(flat)
;
; Gather Variables:
RELHUM = file1->RELHUM
;
; FIXED TO GAUSSIAN GRID SUBROUTINE:
RH_gaus = f2gsh_Wrap(RELHUM,(/nlat,nlon/),0)

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Received on Fri Jun 3 11:22:15 2011

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