How do I create a user-defined SCRIP grid file?

[joanballester_ic3@gmail_com]

Hi all,

I want to create a new user-defined grid, but I need first to generate a SCRIP grid file for the atmosphere and ocean model components (point 1 in page 79 of the CESM1.2 user's guide).

I have successfully generated SCRIP grid files by using the following NCL function:
gridname = "output_filename.nc"
lat = 1d_vector
lon = 1d_vector
opt = True
opt@Mask2D = where(.not.ismissing(mask),1,0)
rectilinear_to_SCRIP(gridname,lat,lon,opt)
However, I need to specify the land/sea mask for the ocean. I assume that I have to interpolate it from a pre-existing out-of-the-box predefined grid file. Is it right? Where could I find this file? Is there any file with very large resolution so that the interpolation does not generate large errors? Should the land/sea mask be a 3D matrix depending on longitude, latitude and depth? (that is, taking into account the bathymetry?).

Many many thanks for your help.
joan

 

[mlevy]

Hi Joan,
If you are using NCL version 6.1 or later, you can use the landsea_mask function. There is a 1x1 mask provided with NCL, so I took your code and inserted the following two lines:

fmask = addfile("$NCARG_ROOT/lib/ncarg/data/cdf/landsea.nc","r")
opt@Mask2D = where(landsea_mask(fmask->LSMASK, lat, lon).eq.0,1,0)

Note that landsea_mask actually provides 5 different types of cells; the example I included will only mask ocean cells but you can include lakes, small islands, or ice shelfs in your mask as well.