fPAR?

[cory_pettijohn@oregonstate_edu]

If someone could please remind me how to pull fPAR out of SurfaceRadiationMod.F90 in CLM3.5, I would greatly appreciate it. Given PAR = 1 - (PARbelowcanopy / PARabovecanopy), is this simply (in CLM state variables):

FPAR = 1 - [ (trd+tri) / (forc_solad + forc_solai) ]

which could probably be simplified... ?

 

[slevis]

Hi,

I'm not familiar with the formulation that you mentioned.

I used FPAR=1-exp(-0.5 LAI) in Levis et al. (1999) JGR-Atm. I'm not sure I included a reference for that in the paper... I think Jon Foley told me about it, and maybe Colin Prentice was using the same as well.

Sam

 

[cory_pettijohn@oregonstate_edu]

Maybe I am overcomplicating this. I want to compare CLM's fPAR against MODIS fPAR. I just need to review my 2-stream physics to understand whether the Beer-Lambert fPAR, calculated using CLM3.5-CN's LAI is necessarily the same fPAR calculated using actual difference between above canopy PAR and below canopy PAR. (by the way, i just realized that I omitted albedo from the forced solar terms above...). I probably am completely off-track on this and confusing radiation terms. thanks for feedback.