[gradsusr] Area integral question

[Ryglicki, Dr. David]

Hi, GrADS users.

I'm brain locking on an area integral on a sphere. If I want to integrate something (Temperature, let's say) on a small section of the sphere (say, 20 N to 40 N, 110 E to 130 E) in mks units in GrADS, I'd start by issuing a command like...

define areaint  = pow(6371000,2)*atot(tmpprs,lon=110,lon=130,lat=20,lat=40)

Would I then have to also multiply by the area of that "square?" (130-110)*(pi/180) * (-cos(40*pi/180) + cos(20*pi/180))
Is this a redundancy with atot? Do I drop the cosine?

I suppose my question comes down to asum vs. atot and how the geometry of the planet is or isn't accounted for. I've read the documentation and I'm having trouble with picturing it mentally (always stunk at geometry).

Thanks.

~Dave
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