[gradsusr] Averaging over multiple dimension ranges

[Ricardo Hallak]

Hi, 
agreed, with exception that it should be: 
size=sizeA1+sizeA2+sizeA3 

since that A1, A2 and A3 are the weights. 
Regards, 
Ricardo 

----- Mensagem original -----

> De: "Bonan Antonino" <abonan at arpa.veneto.it>
> Para: "GrADS Users Forum" <gradsusr at gradsusr.org>
> Enviadas: Quinta-feira, 19 de Setembro de 2013 5:52:40
> Assunto: Re: [gradsusr] Averaging over multiple dimension ranges

> Maybe the correct formula is

> total average =
> ((averageA1*sizeA1)+(averageA2*sizeA2)+(averageA3*sizeA3))/(3*size)

> where

> size = sizeA2 + sizeA2 + sizeA2

> ?

> Dr. Antonino Claudio Bonan
> ----- Original Message -----
> > From: Ivan Toman
> 
> > To: gradsusr at gradsusr.org
> 
> > Sent: Tuesday, September 17, 2013 9:04 PM
> 
> > Subject: Re: [gradsusr] Averaging over multiple dimension ranges
> 

> > Hello,
> 

> > Jeff's idea was to find area sizes with atot function (or asum like
> > I
> > tried). When I know area sizes, I can weight them in total average
> > from three rectangular areas:
> 

> > total average =
> > ((averageA1*sizeA1)+(averageA2*sizeA2)+(averageA3*sizeA3))/3
> 

> > It looks to me that logic is valid.
> 

> > Ivan
> 

> > On 09/17/2013 08:43 PM, Kishore Ragi wrote:
> 

> > > Ivan,
> > 
> 

> > > How can you find the area average with asum? If you can do with
> > > asum,
> > > the same is with aave()/ave() ...
> > 
> 

> > > Anyway, I don't understand what you wanted to calculate.
> > 
> 

> > > Regards,
> > 
> 

> > > Kishore
> > 
> 

> > > On Tue, Sep 17, 2013 at 11:59 PM, Ivan Toman < ivtoman at inet.hr >
> > > wrote:
> > 
> 

> > > > Jeff,
> > > 
> > 
> 

> > > > Option (2) seems to be a logical approach and very nice idea.
> > > > It
> > > > looks to me that asum() also works OK for "measuring" area
> > > > sizes,
> > > > it
> > > > is probably accurate enough.
> > > 
> > 
> 

> > > > Best regards,
> > > 
> > 
> 
> > > > Ivan
> > > 
> > 
> 

> > > > On 09/17/2013 06:57 PM, Jeff Duda wrote:
> > > 
> > 
> 

> > > > > You could either...
> > > > 
> > > 
> > 
> 

> > > > > (1) Knowing the geometry of earth, set up a math problem and
> > > > > solve
> > > > > for the areas of a sphere bounded by such
> > > > > latitudinal/longitudinal
> > > > > coordinates to find the areas of those three regions (I would
> > > > > use
> > > > > spherical coordinates)
> > > > 
> > > 
> > 
> 

> > > > > OR
> > > > 
> > > 
> > 
> 

> > > > > (2) -Create a flat field of ones (e.g., 'define ones =
> > > > > tmp2m/tmp2m')
> > > > 
> > > 
> > 
> 
> > > > > -Use the atot function (grads 2.0.2+ only) to compute the sum
> > > > > of
> > > > > the
> > > > > ones field over your area, which I think should give you the
> > > > > area
> > > > > of
> > > > > each region
> > > > 
> > > 
> > 
> 

> > > > > Then weight each areal average by the area and compute the
> > > > > final
> > > > > weighted average.
> > > > 
> > > 
> > 
> 

> > > > > I've never tried this, so I'm not 100% sure it will work and
> > > > > be
> > > > > accurate. I would play around with the atot function first to
> > > > > see
> > > > > if
> > > > > it really does give you the areas of the regions.
> > > > 
> > > 
> > 
> 

> > > > > Jeff Duda
> > > > 
> > > 
> > 
> 

> > > > > On Tue, Sep 17, 2013 at 11:45 AM, Ivan Toman <
> > > > > ivtoman at inet.hr
> > > > > >
> > > > > wrote:
> > > > 
> > > 
> > 
> 

> > > > > > Hello,
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > If I want to find average value over a lat/lon range, I
> > > > > > would
> > > > > > do:
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > ave(variable,lat=20,lat=21),lon=70,lon=71)
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > However, if I want to do average over multiple areas, for
> > > > > > example:
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > Area 1: lat=20,lat=21 ; lon=60,lon=61
> > > > > 
> > > > 
> > > 
> > 
> 
> > > > > > Area 2: lat=30,lat=31 ; lon=70,lon=71
> > > > > 
> > > > 
> > > 
> > 
> 
> > > > > > Area 3: lat=40,lat=41 ; lon=80,lon=81
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > how can I solve this problem? I can't simply find three
> > > > > > area
> > > > > > averages,
> > > > > 
> > > > 
> > > 
> > 
> 
> > > > > > sum them together and divide by three, because areas are
> > > > > > not
> > > > > > the
> > > > > > same
> > > > > > sizes.
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > Thanks for any hint.
> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > > Regards,
> > > > > 
> > > > 
> > > 
> > 
> 
> > > > > > Ivan Toman
> > > > > 
> > > > 
> > > 
> > 
> 
> > > > > > _______________________________________________
> > > > > 
> > > > 
> > > 
> > 
> 
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> > > > > 
> > > > 
> > > 
> > 
> 
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> > > > > 
> > > > 
> > > 
> > 
> 
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> > > > > 
> > > > 
> > > 
> > 
> 

> > > > > --
> > > > 
> > > 
> > 
> 
> > > > > Jeff Duda
> > > > 
> > > 
> > 
> 
> > > > > Graduate research assistant
> > > > 
> > > 
> > 
> 
> > > > > University of Oklahoma School of Meteorology
> > > > 
> > > 
> > 
> 
> > > > > Center for Analysis and Prediction of Storms
> > > > 
> > > 
> > 
> 

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> > 
> 
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> > > 
> > 
> 
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> > 
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