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0.25 degree, daily SST from AVHRR for data ocean use

R

raeder

Member
I (with help from Bob Tomas and others) have developed domain and mapping
files between 1/4 degree AVHRR SSTs and a 1 degree CAM-FV from CESM1_5_beta03,
including CISM1 (20 km) and MOSART. I'd like this to become available as
a supported DOCN resolution, for use with DART, CAPT, and other short forecast
CAM applications. It would be great if it could be generalized to CAM-SE
and other resolutions of CAM. If this is a possibility for CESM2, how should
I go about it?

I've posted this in bugzilla too, issue 2300.

Thanks,
Kevin
 
R

raeder

Member
I've converted the current AVHRR data, "NOAA Optimum Interpolation 1/4 Degree
Daily Sea Surface Temperature Analysis" (NSF NCAR GDEX Dataset d277007),
into a new 0.25-degree daily file of SST and sea ice coverage for use by CESM.
It spans September 1981 through June 2025.
It was concatentated from several other files.
I checked the continuity of the times and SST field at the time boundaries
of the original files, and there appear to be no discontinuities.
It has not undergone extensive testing yet.

Hopefully this file (avhrr_v2.1.198109-202506_12Z_filled_c250709.nc)
will appear in the CESM input file dataset by end of 2025.
It file is ~36 Gb. If this is too cumbersome to use, I've split it into yearly files.
I've found those to be trickier to use; CESM has (had?) default settings
which allow it to run a different year than the SST file
by using just the first or last 2 dates in the file for every coupling time.
Be careful to understand the parameters that control the use of these files,
and check the log files for the correct date selection.

The scripts and programs which were used to convert this data are documented in
Contact raeder@ucar.edu if you need help getting the file.

There's at least one remaining hurdle to making this a supported resolution in CESM3.
The default CAM dycore is SE and there appear to be no grid files which map between
the 0.25 degree rectangular SST grid and any of the growing number of SE resolutions.
The SE resolution is controlled by both the number of elements along a cube face edge (ne#)
and the number of physics grid points along an element edge (pg#).
It seems that the number of spectral nodes (np#) along each element edge is not a factor.
This seems to imply that the other components interact with the physics grid and not the CAM-SE dycore grid.
There are currently at least 8 ne options
(/glade/campaign/collections/gdex/data/d651077/cesmdata/inputdata/share/scripgrids)
and up to 3 pg options for each.
It seems impractical to generate mapping and grid files for all of these combinations
with all of the other components' resolutions, (especially by me) so I'm wondering
whether there's a CSEG strategy for prioritizing these. @mlevy might be able to provide some context.
 
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