I just looked at the
EXTPAR
source code. As far as I understand now I have misinterpreted the sentence
*
Values that depend on the plant cover, such as
PLCOV
MX,
PLCOV
MN,
LAI
MN,
LAI
MX, RS
MIN
,
FOR
E,
FOR
D,
ROOTDP
and z0, are weighted with the plant cover maximum in addition to the pixel area.
*

This seems to hold only for
GLOBECOVER
and there is a general maximum plant cover in a grid cell defined for this. I mixed it up with the actual plant cover which is a different thing. Therefore I think you are right and for_e and for_d are fractions of the total grid cell and thus the long_names are OK.

From this the equation for zsnow_alb is clear now and it fits to your example for vegetation fraction of 0.8, for_e = 0.4, for_d = 0.3 and veg_low = 0.1.

What the equation for also concerns I can only suspect that the programmer assumed that the fractions for for_e and for_d hold also for the vegetation part not just for the whole grid cell.

Would the following be more appropriate?

zalso(i,j)= zsnow*zsnow_alb + & (1._ireals-zsnow)* & (for_e(i,j)*0.10_ireals + & for_d(i,j)*0.15_ireals + & (zvege-for_e(i,j)-for_d(i,j))*0.20_ireals+ & (1._ireals-zvege)*zalso(i,j))

What do you think?

Anyway, at the end the meaning can only be revealed by the programmer (whom I do not know).

I just looked at the EXTPAR source code. As far as I understand now I have misinterpreted the sentence

Values that depend on the plant cover, such as PLCOV MX, PLCOV MN, LAI MN, LAI MX, RS MIN , FOR E, FOR D, ROOTDP and z0, are weighted with the plant cover maximum in addition to the pixel area.This seems to hold only for GLOBECOVER and there is a general maximum plant cover in a grid cell defined for this. I mixed it up with the actual plant cover which is a different thing. Therefore I think you are right and for_e and for_d are fractions of the total grid cell and thus the long_names are OK.

From this the equation for zsnow_alb is clear now and it fits to your example for vegetation fraction of 0.8, for_e = 0.4, for_d = 0.3 and veg_low = 0.1.

What the equation for also concerns I can only suspect that the programmer assumed that the fractions for for_e and for_d hold also for the vegetation part not just for the whole grid cell.

Would the following be more appropriate?

What do you think?

Anyway, at the end the meaning can only be revealed by the programmer (whom I do not know).