Hi, I am working on a habitat-based PFT/ land cover map over Europe. We first map habitats for present and future conditions, and then translate them into CLM5 PFTs.
I understand that the sum of PCT_NATVEG, PCT_CROP, PCT_URBAN, PCT_GLACIER, PCT_LAKE, PCT_WETLAND needs to be 100%. Over the ocean (i.e. where landmask=0 and landfrac=0), usually PCT_WETLAND=100 and all other landunits =0. However, at the coast (i.e. where landmask=1 and landfrac=[>0,<1]), PCT_WETLAND=0 and all other landunits=[>0,<=100].
My interpretation is that PCT_WETLAND (which has been removed as a "wetland landunit" as of CLM4.5) just serves as a dummy landunit over pure ocean cells that do not run in CLM anyways. Land cells at the coast that do run have their land unit fractions specified for the land part only (e.g. a cell with 70% ocean and 30% land covered by trees would have landfrac=0.3 and PCT_NATVEG=100). Fluxes are calculated as if the full cell was forest (also reflected in the output) and are scaled by frac from the domain file at the coupler. Is it correct that all landunits are in relation to the land part only (except PCT_WETLAND over ocean acting as a dummy)?
Also, I understand that LANDFRAC_PFT appears in fsurdat for convenience and isnot used by CLM (instead, frac from the domain file is passed to the history files). They are allowed to differ theoretically and I think they do in practice (as noted in this thread). Anyway, how is LANDFRAC_PFT defined/calculated, and how can it be used? E.g. in my case for constructing a new land cover map, can/should I use it to separate land (natveg including wetland, crop, urban, glacier, lake) from ocean areas? Or should I rather use frac from the domain file for this?
I understand that the sum of PCT_NATVEG, PCT_CROP, PCT_URBAN, PCT_GLACIER, PCT_LAKE, PCT_WETLAND needs to be 100%. Over the ocean (i.e. where landmask=0 and landfrac=0), usually PCT_WETLAND=100 and all other landunits =0. However, at the coast (i.e. where landmask=1 and landfrac=[>0,<1]), PCT_WETLAND=0 and all other landunits=[>0,<=100].
My interpretation is that PCT_WETLAND (which has been removed as a "wetland landunit" as of CLM4.5) just serves as a dummy landunit over pure ocean cells that do not run in CLM anyways. Land cells at the coast that do run have their land unit fractions specified for the land part only (e.g. a cell with 70% ocean and 30% land covered by trees would have landfrac=0.3 and PCT_NATVEG=100). Fluxes are calculated as if the full cell was forest (also reflected in the output) and are scaled by frac from the domain file at the coupler. Is it correct that all landunits are in relation to the land part only (except PCT_WETLAND over ocean acting as a dummy)?
Also, I understand that LANDFRAC_PFT appears in fsurdat for convenience and isnot used by CLM (instead, frac from the domain file is passed to the history files). They are allowed to differ theoretically and I think they do in practice (as noted in this thread). Anyway, how is LANDFRAC_PFT defined/calculated, and how can it be used? E.g. in my case for constructing a new land cover map, can/should I use it to separate land (natveg including wetland, crop, urban, glacier, lake) from ocean areas? Or should I rather use frac from the domain file for this?
