[Wrf-users] Metgrid SST interpolation

Dominikus Heinzeller climbfuji at ymail.com
Wed Mar 19 10:38:32 MDT 2014

Hi Ségolène,

The problem is that the coarse resolution ERA-INTERIM data (75km) is interpolated along with your finer resolution geogrid data. Along the coast, the two landmasks do not match up and you get strange effects. Trialling different interpolation options can help but often does not remove the problem. Depending on your simulation period, you can substitute the ERA-INTERIM SST field (and landmask for interpolating this field) with NCDC SST data at 25km resolution available from the GHRSST website (data from late 1981 to early 2014). Other SST data at even higher resolution (down to 1km!) is also available from this website, but mostly for much shorter periods.



On 19/03/2014, at 11:49 am, Ségolène Berthou <segolene.berthou at lmd.polytechnique.fr> wrote:

> Dear WRF users,
> I have some troubles with the generation of the SST in the met_em files : the interpolation is bad near the coasts with cold SST near the coasts. I feel like I have tried all the possible configurations of interpolation and landmask (LANDSEA and LANDMASK) in the METGRID.TBL.ARW.
> However, the problem seems to be recurrent. Do you have an idea of what interpolation/landmask I can use or where the problem comes from? Does it come from geogrid?
> I am using FILES generated from ERA-interim GRIB files.
> You can find attached
> - the SST in metgrid files: on the left, the one I get, on the right: the one I am looking for (older simulation)
> - the landmask: on the left, the one from ERA-interim, on the right: the one from WRF.
> Here is the METGRID.TBL configuration that corresponds to the figure shown:
>        interp_option=sixteen_pt+four_pt+nearest_neighbor+wt_average_4pt+search
>        mandatory=yes    # MUST HAVE THIS FIELD
>        masked=land
>        interp_mask=LANDMASK(1)
>        fill_missing=0.
>        missing_value=0.
> Thank you very much in advance,
> Ségolène Berthou
> <SST.png><LANDMASK.png>_______________________________________________
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