revision r 2566 ) , based on a domain-averaged structure factor

In order to better simulate heat fluxes over multilayer ecosystems, in particular :: for :::::::: example, : tropical forests and savannahs, the next generation of Earth system models will likely include vertically-resolved vegetation structure and multilevel energy budgets. We present here a multi-level radiation ::: flux : transfer scheme which is capable of being used in conjunction with such methods. It is based on a previously established scheme which encapsulates the three dimensional nature of canopies, through the use of a domain-averaged structure factor, referred to here as the effective leaf area index. The :::::::: radiation fluxes are 5 tracked throughout the canopy in an iterative fashion until they escape into the atmosphere or are absorbed by the canopy or soil; this approach explicitly includes multiple scattering between the canopy layers. A series of tests show that the results from the two-layer case are in acceptable agreement with those from the single layer, although the computational cost is necessarily increased due to the iterations. :: For ::: the :: 2 :::: level :::: case ::::: fewer ::: than ::: 15% :: of ::::: results :::::: across ::: the :::::: variable ::::: range :::: have :: a ::::::::: divergence :::::: greater ::: than ::::: 0.01, ::::: fewer :::: than : 2% :::::: greater :::: than :::: 0.02, :::: and :::: none :::: have : a :::::::::: divergence :::::: greater ::: than ::::: 0.03. The ten-layer case is less precise, but 10 still provides results to within an acceptable range ::: (40% : of :::::: results ::::: across ::: the ::::::: variable ::::: range :::: have : a ::::::::: divergence :::::: greater :::: than ::::: 0.01, :: 10% ::::: across ::: the ::::::: variable ::::: range ::::: have : a :::::::::: divergence :::::: greater :::: than ::::: 0.03, :::::: though ::: just ::: 1.5% ::::: greater :::: than ::::: 0.05). This new approach allows for the calculation of radiation :::: flux transfer in vertically resolved vegetation canopies :: as simulated in global circulation