Sunshine hours data is not available in the study basin, but we do have sunshine hours information in El Yeso reservoir (located 82 Km. south of Navarro's creek basin, Location map can be found here.) for the complete study period.
We transferred sunshine hours information to solar radiation through the following expression.
Where:
n: sunshine hours [hours].
N: daily mean hours of the bright sunshine [hours].
Ra: Solar extraterrestrial radiation [W/m2].
Daily mean hours of the bright sunshine is a parameter that depends on the latitude and day of the year. Its values are tabulated for a range of latitudes; we did a linear interpolation in order to adjust this parameter to Navarro's creek location.
Figure: Daily mean hours of bright sunshine, adjusted to Navarro's creek location.
On the other hand, solar extraterrestrial radiation it is calculated at the top of the atmosphere assuming a flat and horizontal surface. The methodology applied is the same one proposed by University of Santa Clara. (more info.)
Figure: Extraterrestrial radiation Sept '07-Feb 08' adjusted to Navarro's creek basin.
Following the procedure described above, it is possible to obtain incident solar radiation distributed day by day. However, all the variables involved must be distributed both spatially and temporally.
In order to obtain a spatial distribution of the incident solar radiation, we applied a radiative gradient based on pixel elevation. (Dirección General de Aguas - Chile, 1995)
Finally obtained results are:
Figure: Spatially distributed incident solar radiation [W/m2] in Navarro's creek basin. To the left Sept 1st 2007, to the right October 7th 2007.
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