Hi Markus,
I can think of a couple of things to be added to the manual page: much of
which I would be happy to write.
1. clarification on units : i.e. in light of current discussion (no pun
intended ! ) it would be good to give a brief overview of radiant energy:
comparing what r.sun models to the output of a common sensor.
2. a quick example on using monthly , or as hamish suggested daily
interpolated, linke turbidity values - i.e. bash style, or something like:
# next revision: based on visual inspection
linke_monthly[1]=5.9
linke_monthly[2]=5.8
linke_monthly[3]=5.6
linke_monthly[4]=5.6
linke_monthly[5]=5.3
linke_monthly[6]=5.0
linke_monthly[7]=4.8
linke_monthly[8]=5.0
linke_monthly[9]=5.0
linke_monthly[10]=5.2
linke_monthly[11]=5.4
linke_monthly[12]=5.6
-------- example script for modeling an entire year -----------------------
#load an array with monthly linke turbidity factors for a mountainous area:
for i in `seq 1 31`; do linke[$i]=${linke_monthly[1]}; done
for i in `seq 32 59`; do linke[$i]=${linke_monthly[2]}; done
for i in `seq 60 90`; do linke[$i]=${linke_monthly[3]}; done
for i in `seq 91 120`; do linke[$i]=${linke_monthly[4]}; done
for i in `seq 121 151`; do linke[$i]=${linke_monthly[5]}; done
for i in `seq 152 181`; do linke[$i]=${linke_monthly[6]}; done
for i in `seq 182 212`; do linke[$i]=${linke_monthly[7]}; done
for i in `seq 213 243`; do linke[$i]=${linke_monthly[8]}; done
for i in `seq 244 273`; do linke[$i]=${linke_monthly[9]}; done
for i in `seq 274 304`; do linke[$i]=${linke_monthly[10]}; done
for i in `seq 305 334`; do linke[$i]=${linke_monthly[11]}; done
for i in `seq 335 365`; do linke[$i]=${linke_monthly[12]}; done
export linke
#loop through each day in the year
time \
for x in `seq 1 365`
do
echo "Running r.sun for day $x: Linke turbidity factor= ${linke[$x]}"
r.sun --o -s elevin=$elev aspin=$aspect slopein=$slope \
diff_rad=diffuse_0$x beam_rad=beam_0$x insol_time=time_0$x refl_rad=refl_0$x \
day=$x \
lin=${linke[$x]}
done
-------- example script for modeling an entire year -----------------------
3. a bit of background / or ideas (i have the references handy) on calculating
estimated linke turbidity values from local weather station data. I have yet
to do this with my project, as i am having a tough time with the equations.
should have this worked out soon.
I need to write-up most of these things for my MS thesis anyways, so i would
be happy to contribute to the manual. Obviously review by Jaro and the solar
gang would be a good idea.
Cheers,
Dylan
On Friday 01 December 2006 00:26, Markus Neteler wrote:
hi Dylan,
since I soon have to work with r.sun, too, I would highly appreciate
if you could add your findings to the manual page.
You/others pointed out some things which should/could be clarified
there, please do so while memory is still fresh.
Probably also a small text chunk about the units doesn't harm.
thanks in advance
Markus
Dylan Beaudette wrote on 12/01/2006 06:10 AM:
> Sorry for the noise, it looks like this was an operator error on my part.
>
> Cheers,
>
> Dylan
>
> PS: with even better results from r.sun:
>
> http://169.237.35.250/~dylan/temp/11-yr_variation_vs_modeled.png
>
> when using longer term averages, the R^2 goes to 0.95 ! (right hand
> sub-figure), but still working on optimal Linke turbidity values.
>
> On 11/28/06, Dylan Beaudette <dylan.beaudette@gmail.com> wrote:
>> Hi everyone,
>>
>> I am repeating an experiment, originally conducted Feb 7th 2006,
>> comparing the
>> output from r.sun with real data from a weather station.
>>
>> On Feb 7th, 2006 the output from r.sun (computed with customized linke
>> turbidity values) very closely matched the weather station data.
>>
>> As of today the exact same experiment gives slightly different results:
>> 1. the correlation between r.sun and the weather station is nearly
>> identical
>> 2. the output from r.sun (specifically the beam component) is about 1500
>> Wh/sq. meter/day higher than it should be.
>>
>> The only thing that has changed since I last conducted this
>> experiment was
>> r.sun. From the CVS server it looks like r.sun/main.c was altered
>> shortly
>> after I did my original experiment:
>>
>> ------------------------------------------------------------------------
>>-----------------------
>>
>> Revision 2.14 / (as text) / (view) - annotate - [select for diffs] ,
>> Tue Feb
>> 21 10:00:52 2006 UTC (9 months ago) by markus
>> Branch: MAIN
>> Changes since 2.13: +28 -174 lines
>> Diff to previous 2.13
>>
>> Jaro Hofierka: new shadow algorithm; dist param changed to fixed value;
>> correction factor for shadowing to account for the earth curvature
>> ------------------------------------------------------------------------
>>-----------------------
>>
>> http://freegis.org/cgi-bin/viewcvs.cgi/grass6/raster/r.sun/main.c
>>
>>
>> In summary, the diffuse component of the modeled solar radiation is
>> nearly the
>> same as it was when computed by r.sun Feb 7 2006. The beam component
>> is now
>> about 1500 Wh/sq m / day higher than it was as on Feb 7 2006.
>>
>> This brings up an interesting question: which results from r.sun
>> where the
>> most representative of reality ? I noticed that the changes made to
>> r.sun
>> involved a shadow algorithm- yet my weather station (and modeled
>> area) are
>> not greatly affected by the shadowing of adjacent terrain.
>>
>> Any thoughts on how to best proceed would be greatly appreciated.
>>
>> PS:
>> the original results were mentioned in a previous message to the
>> GRASS list
>> on Feb 8 2006.
>> http://www.nabble.com/-GRASSLIST%3A10214--some-nice-results-from-r.sun-t
>>1087635.html
>>
>>
>> --
>> Dylan Beaudette
>> Soils and Biogeochemistry Graduate Group
>> University of California at Davis
>> 530.754.7341
>>
>> _______________________________________________
>> grass-dev mailing list
>> grass-dev@grass.itc.it
>> http://grass.itc.it/mailman/listinfo/grass-dev
>
> _______________________________________________
> grass-dev mailing list
> grass-dev@grass.itc.it
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--
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341
