Cross section using maskout for terrain

[Dan Leins]

All,

I am attempting to draw a simple cross section showing temperature across a
model domain and I would like to maskout the area below ground. I have seen
some traffic on this issue. I see that I should be able to define the
terrain by subtracting pressfc/100 from lev, with all negative values being
areas that are underground. Then using maskout, I can do the following:

d maskout(tmpprs,t1pm1-lev)

This gives me something in the ballpark of what I'm looking for
(image1.png), but the shaded area looks very gridded in nature. When I
simply plot a contoured plot of 't1pm1-lev', it doesn't look gridded at all
and appears nice and smooth (image2.png). The model grid spacing is 4km and
I'm covering about 500km in my cross section so I'm guessing things should
appear relatively smooth.

Why does maskout produce results that look so gridded?   Is there any other
way I can maskout the underground areas but still have a nice crisp outline
of the terrain?

Thanks!
Dan Leins
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