shaded and sunlit fractions

After updating the calculations, the VOM optimized towards extremely low LAI, close to zero. It has to do with the following.

The equation for the sunlit LAI is the following, from Campbell and Norman (1998):

the Kbe(phi) here is a function of zenith and leaf angle distribution. The function above looks like this then:

However, if we calculate the relative fractions of sun and shaded leaves, it is this:

So the VOM optimized towards a low LAI, to have a sunlit fraction close to 1.

@stanislaus.schymanski, do you think that we should actually multiply with LAIsun and LAIshade instead? Cause then the VOM would try to maximize LAIsun, but that goes together with the increasing cost of more shade.

Another approach could be to use LAIsun and LAIshade to calculate and fpar_sun and fpar_shade, with Lambert-Beer. And then multiply with those fractions instead. So like this:

                   fpar_sunt(ii) = 1.0d0 - p_E ** (-lat_sun(ii) * kappa * sqrt(i_alpha_abs) )                     
              
                
                   jactt(:,ii)   = (1.d0 - p_E ** (-(i_alpha * (pardir_h(th_) + pardiff_h(th_)) ) &    
        &             / jmaxt_h(:))) * jmaxt_h(:) * fpar_sunt(ii)

What do you think?