[GRASS-user] [GRASSLIST:1178] how to use cloud cover with r.sun?

[Hamish]

Massimiliano Cannata wrote:
> Actually I don't really know what is the influence of cloud cover on 
> radiation (linear function between cloud cover and energy
> filtered????),

on a cloudy day the direct sunlight is reduced, and the diffuse in
increased. e.g. in the fjords I study there are many places which
never get direct sunlight. We have deployed subsurface PAR light-loggers
in paired sunny/shaded sites and the shaded side actually gets more
light on cloudy days.


Hamish