Subject: Re: photosynthesis calculations
From: Charlie Zender (zender@heinlein.cgd.ucar.EDU)
Date: Fri Jul 04 1997 - 12:44:42 MDT
Dear Ranga,
You say you are using T31 horizontal resolution a "48x48 matrix", yet
when I check to see what the Gaussian grid is for T31, I find it is
48x96, not 48x48. Thus when I compute the area of a gridcell in the
southernmost latitude circle, -87.1591 degrees, I get an answer of
8375 km2, which is approximately half your value (I used
radius_earth=6.370e+06 m).
> T31x15 Resolution
> CCM LAT GRID CELL
> INDEX AREA (km*km)
> 1.0 17786.436
So either I do not understand the grid you are using or there maybe is
a factor of two missing from your calculations.
Also, I noticed that your values for surface area are not exactly
symmetric about the equator as they should be. This makes me wonder if
you are using Gaussian weights to calculate surface area? I recommend
doing so if you are not already. Contact me directly if the method for
doing so is unclear. The rest of your calculation method looks fine to
me, but I have never used "FPSN" before.
Good luck,
Charlie
-- Charlie Zender Voice, FAX: (303) 497-1612, 497-1324 NCAR ASP & CGD E-mail: zender@ncar.ucar.edu P.O. Box 3000 URL: http://www.cgd.ucar.edu/cms/zender Boulder CO 80307-3000 PGP: finger -l zender@heinlein.cgd.ucar.edu
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