Estimation of diffuse and direct radiation starting from the global radiation

[FrancescoP]

I don’t know if this one is the appropriate forum for the following question. If for this question it is better another section of the forum, point out to me, please.
I know the global radiation on a south oriented surface, in a German locality. Do you know methods to estimate the direct component and the diffuse component? I found an article very interesting

C.J.T. Spitters, H.A.J.M. Toussaint e J. Goudriaan, “Separating the diffuse and direct component of global radiation and its implications for modeling canopy photosynthesis Part I. Components of incoming radiation”, Agricultural and Forest Meteorology, Amsterdam, Elsevier Science Ltd., Volume 38, Issues 1-3, ottobre 1986, pp. 217-229

but unfortunately it isn’t useful in my case because as input data it presents the radiation on a horizontal surface, not on a south oriented surface.

With Regards
Francesco

 

[Andy Resnick]

Are referring to the direct component from the sun, and the diffuse component from everywhere else?

I was only able to pull up the abstract, but based on that, it agrees with my suspicion- given a single measurement of the total (hemispherical) incidance, you cannot uniquely separate the direct and diffuse component. Those guys have a model; there are many models. Mostly people try and model BRDFs, but the concept is closely related to your problem.

http://www.pa.op.dlr.de/ISIS/
http://www.ecd.bnl.gov/pubs/BNL67010.pdf
http://modis.gsfc.nasa.gov/about/design.php
http://www-modis.bu.edu/brdf/userguide/intro.html

Other applications are heat transfer and remote sensing, you may find some good information that way.