[GRASS-user] running r.sun with ancillary layers.

[Giuseppe Amatulli]

Hi,
I need some suggestions to run r.sun and use the
Albedo-Modis<http://modis-atmos.gsfc.nasa.gov/ALBEDO/index.html>product
as an input for the r.sun albedo parameter.
Albedo-Modis <http://modis-atmos.gsfc.nasa.gov/ALBEDO/index.html> has two
main products: *White-sky and  ** Black-sky*
"

*White-sky is the bihemispherical reflectance under conditions of isotropic
illumination, so it has the angular dependency removed. Black-sky is the
directional hemispherical reflectance computed at local solar noon."*
Which one of these is the most appropriate to use?

Moreover, "white-sky" and "black-sky" are computed at 10 wavelengths
(0.47µm, 0.55µm, 0.67µm, 0.86µm, 1.24µm, 2.1µm, 0.3-0.7µm, 0.3-5.0µm, and
0.7-5.0µm).
Which one is the most appropriate to use?

The only info that i found for this is


*i.albedo calculates the Albedo, that is the Shortwave surface reflectance
in the range of 0.3-3 micro-meters. It takes input of individual bands of
surface reflectance from Modis, AVHRR, Landsat or Aster and calculates the
Albedo for those. This is an precursor to r.sun and any Energy-Balance
processing. *
so the 0.3-5.0µm should be the more suitable for this purpose. Correct?

My final aim is to use ancillary layers to "fill" all the different
parameters  of  r.sun.
All the examples that i found use constant or default values.
May anyone point to me some source of information?

Thanks in Advance


-- 
Giuseppe Amatulli, Ph.D.

Center for Earth Observation
ESC Room 119A
Yale University
P.O. Box 208109
New Haven, CT, 06520-8109
Teaching: spatial-ecology.net
Work:  <http://www.exeter.ac.uk/esi/people/casalegno/>
http://sbsc.yale.edu/training-and-support
<http://www.spatial-ecology.net>
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