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Wouter,<br>
<br>
I've done extensive work with precipitation data in the Ohio River
Valley in the U.S. (~450,000 km^2) looking at both raingauge and radar
derived precipitation accumulations. Generally, I have only looked at
monthly, seasonal, and annual amounts. In complex terrain I just have
no feel for the strength of the orographic influence at shorter time
scales. Having said that, however, from some research that has been
done, I know that for isolated storms (some flash flood producing
convective events) there can be terrain focusing of the storm cells.<br>
<br>
I have used the techniques suggested by Goovaerts (cited below) using
ordinary kriging with variable means, but I have not verified the
estimates independently yet.<br>
<br>
I certainly would like to have a better understanding of the orographic
influence at shorter time scales, especially in the Appalachian
Mountains of the U.S. which generally have local relief on the order of
1000 m.<br>
<br>
Regards,<br>
Tom Adams<br>
<br>
<br>
DrakeGis wrote:<br>
<blockquote type="cite"
cite="mid33455.141.211.77.230.1098968585.squirrel@cafemail.giscafe.com">
<pre wrap="">HI,
I'm not so sure about using Thiessen is a really good option. I know
that usually is the easier way, but Goovaerts, P (2000) in
"Geostatistical approaches for incorporating elevation into the spatial
interpolation of rainfall (Journal of Hydrology, 228 (1-2):113-129)"
presents a really good analysis of the different techniques (prior to
incorporate the elevation data) and some tools to improve the
estimations, toghether with analysis of accurancy. He also conclude that
Kriging is a better option.
D.
</pre>
<blockquote type="cite">
<pre wrap="">Hello,
I'm aware that my question is not really GRASS related, but none of our
GIS experts can help me, so I hope someone here can point me to a
relevant paper or study.
I want to aggregate daily rainfall data of 3 rain gauges in a small
catchment for input in a lumped hydrological model
Herefore, I am using a weighted average, based on the relative area of
the respective Thiessen polygons.
Now I'm looking for a technique to determine the uncertainty on the
result, based on the variability between the 3 rain gauges.
If someone can help me, this would be greatly acknowledged!
Thanks,
Wouter Buytaert
</pre>
</blockquote>
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<br>
<pre class="moz-signature" cols="72">--
Thomas E Adams
National Weather Service
Ohio River Forecast Center
1901 South State Route 134
Wilmington, OH 45177
EMAIL: <a class="moz-txt-link-abbreviated" href="mailto:thomas.adams@noaa.gov">thomas.adams@noaa.gov</a>
VOICE: 937-383-0528
FAX: 937-383-0033</pre>
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