[gradsusr] aave VS amean

Jennifer Adams jma at cola.iges.org
Mon Aug 17 11:18:55 EDT 2015

Use aave when your data is on a lat/lon grid, use amean when your data are on an abstract or non-earth-based grid. The amean function assumes all gridpoints have equal areas and get equal weights. The aave funciton applies a weighting based on the sine of the latitude. If you are looking at data on a curvilinear grid, then you are probably interpolating it to a regular lat/lon grid using PDEF, in which case you should use aave(). 

On Aug 7, 2015, at 3:29 PM, LI Qi <liqi123sh at qq.com> wrote:

> Dear grads community,
> Forgive what is probably a stupid question, but I do not really know the difference between the two.
> I check the docu, and it says:
> aave     area average with latitude weighting
> amean    area means are not weighted by latitude. Means are weighted by grid interval to account for non-linear grid spacing.
> My question is:
> [1] when to use aave and when amean? why?
> [2] if I have data A on a regular lon/lat grid, and data B on a curvilinear grid, both at regional scale, which function should I use? and what about at global scale?
> Thanks a lot!
> Qi
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Jennifer M. Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
111 Research Hall, Mail Stop 2B3
George Mason University
4400 University Drive
Fairfax, VA 22030 

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