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<div class="moz-cite-prefix">Hello,<br>
<br>
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:<br>
<br>
total average =
((averageA1*sizeA1)+(averageA2*sizeA2)+(averageA3*sizeA3))/3<br>
<br>
It looks to me that logic is valid.<br>
<br>
Ivan<br>
<br>
<br>
<br>
On 09/17/2013 08:43 PM, Kishore Ragi wrote:<br>
</div>
<blockquote
cite="mid:CAN4rXbQ+dK4QGavgaYLv88p5avPRrABBMB8xvTwvLj0aMdxViA@mail.gmail.com"
type="cite">
<div dir="ltr">Ivan,
<div><br>
</div>
<div>How can you find the area average with asum? If you can do
with asum, the same is with aave()/ave() ... </div>
<div><br>
</div>
<div>Anyway, I don't understand what you wanted to calculate. <br>
</div>
<div><br>
</div>
<div>Regards,</div>
<div><br>
</div>
<div>Kishore</div>
<div><br>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Tue, Sep 17, 2013 at 11:59 PM, Ivan
Toman <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:ivtoman@inet.hr" target="_blank">ivtoman@inet.hr</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Jeff,<br>
<br>
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.<br>
<br>
Best regards,<br>
Ivan
<div>
<div class="h5"><br>
<br>
<br>
On 09/17/2013 06:57 PM, Jeff Duda wrote:<br>
</div>
</div>
</div>
<div>
<div class="h5">
<blockquote type="cite">
<div dir="ltr">
<div>
<div>
<div>
<div>
<div>You could either...<br>
<br>
</div>
(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)<br>
<br>
</div>
OR<br>
<br>
</div>
(2) -Create a flat field of ones (e.g.,
'define ones = tmp2m/tmp2m')<br>
</div>
-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<br>
<br>
Then weight each areal average by the area and
compute the final weighted average.<br>
<br>
</div>
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.<br>
<div><br>
Jeff Duda<br>
</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Tue, Sep 17, 2013 at
11:45 AM, Ivan Toman <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:ivtoman@inet.hr"
target="_blank">ivtoman@inet.hr</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">Hello,<br>
<br>
If I want to find average value over a lat/lon
range, I would do:<br>
<br>
ave(variable,lat=20,lat=21),lon=70,lon=71)<br>
<br>
<br>
However, if I want to do average over multiple
areas, for example:<br>
<br>
Area 1: lat=20,lat=21 ; lon=60,lon=61<br>
Area 2: lat=30,lat=31 ; lon=70,lon=71<br>
Area 3: lat=40,lat=41 ; lon=80,lon=81<br>
<br>
how can I solve this problem? I can't simply
find three area averages,<br>
sum them together and divide by three, because
areas are not the same sizes.<br>
<br>
Thanks for any hint.<br>
<br>
Regards,<br>
Ivan Toman<br>
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<br>
<br clear="all">
<br>
-- <br>
Jeff Duda<br>
Graduate research assistant<br>
University of Oklahoma School of Meteorology<br>
Center for Analysis and Prediction of Storms<br>
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