Hi all,
I ran a simulation with BSSP585 compset using cesm2.1.2. I switched to use SP mode.
Now I am trying to calculate the effective emissivity for rural, tree, grass, and bare soil land tiles (the tree and grass land tiles include all the tree and grass PFTs). I know that the emissivity of bare soil is 0.96 and I can calculate the emissivity of vegetation by : emi_veg=1-exp(-(L+S)/mu) in the Eq.2.4.20 of CLM5 Tech note (2.4. Radiative Fluxes — ctsm release-clm5.0 documentation). The L and S stand for LAI and SAI, respectively, and mu is 1.0.
The way I calculate the rural emissivity is :
1. calculate the annual L+S for each PFT and CFT.
2. calculate the emissivity for each PFT and CFT using Eq.2.4.20
3. Calculate the area-weighed mean emissivity of all PFTs (including bare soil whose emissivity is 0.96) and CFTs.
I expect the rural emissivity to be 0.96-0.98 but I got some very low rural emissivity (0.4-0.6) in some mid- to high-latitude areas (Figure attached). I wonder if I missed something here (snow cover over vegetation?). What is the best way to calculate the effective rural (and tree/grass land tile) emissivity?
Thank you very much!
I ran a simulation with BSSP585 compset using cesm2.1.2. I switched to use SP mode.
Now I am trying to calculate the effective emissivity for rural, tree, grass, and bare soil land tiles (the tree and grass land tiles include all the tree and grass PFTs). I know that the emissivity of bare soil is 0.96 and I can calculate the emissivity of vegetation by : emi_veg=1-exp(-(L+S)/mu) in the Eq.2.4.20 of CLM5 Tech note (2.4. Radiative Fluxes — ctsm release-clm5.0 documentation). The L and S stand for LAI and SAI, respectively, and mu is 1.0.
The way I calculate the rural emissivity is :
1. calculate the annual L+S for each PFT and CFT.
2. calculate the emissivity for each PFT and CFT using Eq.2.4.20
3. Calculate the area-weighed mean emissivity of all PFTs (including bare soil whose emissivity is 0.96) and CFTs.
I expect the rural emissivity to be 0.96-0.98 but I got some very low rural emissivity (0.4-0.6) in some mid- to high-latitude areas (Figure attached). I wonder if I missed something here (snow cover over vegetation?). What is the best way to calculate the effective rural (and tree/grass land tile) emissivity?
Thank you very much!