problems regridding CCSM CICE grid

From: David B. Reusch <dreusch_at_nyahnyahspammersnyahnyah>
Date: Mon Mar 18 2013 - 11:37:06 MDT


I have run into a problem trying to regrid CCSM CICE data to the CCSM
atmospheric grid. Inexperience with the CICE grid may be part of what's
going on but I'm also seeing weirdness in NCL plotting of regridded
data. (See for the atm grid I want to regrid to.)

The CICE grid (as I understand it and based on looking at plots, etc.)
is basically a normally spaced lat/lon grid in the SH (the part I care
about) and a shifted pole in the NH (to over Greenland so the sea ice
and ocean models can function over the North Pole). See

When I use ESMF to regrid (see define_src.ncl, define_tgt.ncl,
define_wts.ncl, do_regrid.ncl), the general picture looks "ok" but there
are gaps at ~40 deg W and 0 deg. The former is probably due to this
being the edge of the CICE grid, but the latter is a mystery. The SH
looks ok other than this. The NH starts to get weird beginning with
something at the equator, between the two longitude gaps that goes off
in a tail to the west. The Greenland pole area is also nearly free of
grid points, though I don't know if this is expected or not. See and for plots of the
regridded grid points.

I'd at least like to fix the gaps at ~40 deg W and 0 deg and I'd be
happier if the NH weirdness went away (but it's not essential, I think).

Ignoring the above gridpoint issues, when I proceed with
gsn_csm_contour_map_polar, things get ugly in the area west of 0 deg
with contours that just don't make any sense (see
Although cnFillMode only affects contour filling, not where the contours
go, I also tried cellfill and rasterfill to see what happened. In
raster fill this same area of wacky contours is left blank, making me
wonder if there's something going wrong in NCL vs. it just being my data

I've uploaded ncl_report2_dbr.tgz to the ftp site (ignore
ncl_report.dbr.tgz, it's missing ps files). In addition to the already
mentioned ncl and ps files, it has:
- the target grid
- the source grids and sea ice data to be regridded
- the regridded data
-,, ESMF files
- ccsm_atm_ll.ncl, ccsm_ice_ll.ncl, ccsm_plot.ncl NCL to plot atm grid,
ice grid, sea ice data
- ccsm_atm_ll*.ps atm grid plots
- ccsm_ice_ll*.ps ice grid plots, original and regridded

Note that the reason for this regridding is to take advantage of
existing code that uses the CCSM atm grid for creating WRF WPS
intermediate files from netCDF files.


Associate Research Professor of Climatology
Dept of Earth and Environmental Science
MSEC 304; 801 Leroy Place
New Mexico Tech
Socorro, NM 87801
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Received on Mon Mar 18 11:37:25 2013

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