[gradsusr] area average method

[hersala]

Dear Satyaban:
An old printable manual for GrADS (V1.5.1.12) that can be found here:

ftp://grads.iges.org/grads/beta/doc/gadoc151.pdf

says in pages 71-72:

*3) The aave function assumes that the world coordinates are longitude in
the X dimension and latitude in the Y dimension, and does weighting in the
latitude dimension by the delta of the sin of the latitudes. Weighting is
also performed appropriately for unequally spaced grids.

*I hope this can solve your question.
Regards

Hernán



2010/8/16 Satyaban BishoyiRatna <satya_atmos at rediffmail.com>

>
> Dear Hernán Sala,
> I missed 'a' during typing for 'aave' in the second method.
> In both the methodology working for 'area average' but which method we
> should follow. I think the first method will use the map scale factor for
> calculate area average. Is it really required or 'aave' command will be
> enough ?
> I didn't find any document to use map scale factor for area average
> calculation.
>
> Thanks.
> Satyaban
>
> On Tue, 17 Aug 2010 05:36:19 +0530 wrote
>
> >Dear Satyaban:
> I suggest you to see the function aave. You will find more information in:
> http://www.iges.org/grads/gadoc/gadocindex
> I have used it, for instance, with temperatures from NCEP reanalysis model.
>
>
> Regards,
> Hernán Sala
> Instituto Antártico Argentino
>
>
>
> 2010/8/16 Satyaban BishoyiRatna
>
>
>
> Dear User,
>
> I saw some script, where people follow two method to calculate the area
> average value of a specific parameter.
>
>
>
> First method is:
>
> 'tmp1=ave(tmp*cos(lat*(3.14/180.)),lat=5,lat=50)'
>
> 'tmp2=ave(tmp1,lon=40,lon=120)'
>
> 'd tmp2'
>
>
>
> Second method is:
>
> 'tmp1=ave(tmp,lon=60,lon=100,lat=7,lat=40)'
>
> 'd tmp1'
>
>
>
> Which method one should follow and what the difference one should get.
>
>
>
> Thanks.
>
> Regards
>
> Satyaban
>
> ########################################################
>
> Dr. Satyaban Bishoyi Ratna
>
> CDAC, Pune, India
>
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> Dr. Satyaban Bishoyi Ratna
> CDAC, Pune, India
>
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