A 2-LEAF MODEL FOR CANOPY CONDUCTANCE, PHOTOSYNTHESIS AND PARTITIONING OF AVAILABLE ENERGY-I - MODEL DESCRIPTION AND COMPARISON WITH A MULTILAYERED MODEL
Yp. Wang et R. Leuning, A 2-LEAF MODEL FOR CANOPY CONDUCTANCE, PHOTOSYNTHESIS AND PARTITIONING OF AVAILABLE ENERGY-I - MODEL DESCRIPTION AND COMPARISON WITH A MULTILAYERED MODEL, Agricultural and forest meteorology, 91(1-2), 1998, pp. 89-111
An one-layered, two-leaf canopy model which calculates the fluxes of s
ensible heat, latent heat and CO(2)( )separately for sunlit and shaded
leaves is presented. The two-leaf model includes: (1) a simple but ro
bust radiation model, (2) an improved leaf model accounting for the in
teraction of conductance and photosynthesis and the response of stomat
a to water vapour pressure deficit and available soil water and (3) a
new parameterisation of radiative conductance which simplifies solutio
n of the leaf energy balance equation. Comparisons with a multi layere
d model show that predicted fluxes of CO2, latent and sensible heat fl
uxes usually agree within 5% over a range leaf area index typical of a
wheat crop grown in a temperate climate. The two-leaf model is comput
ationally 10 times more efficient than the multi-layered model and is
suitable for the incorporation into regional and global climate models
. For a hypothetical canopy with a leaf area index of 5 under very dry
(vapour pressure deficit of air of 2 kPa) and sunny conditions, the n
et canopy photosynthesis and latent heat fluxes calculated by the two-
leaf model agree with those by the multi-layered model within 10% for
the whole range of soil water conditions (from very dry to wet) and th
e sensible heat fluxes of the canopy calculated by the two-leaf model
agree with those by the multi-layered model within 25 W m(-2) (or usua
lly within 15%). For a canopy with leaf area index less than 2, the di
fferences in the modelled fluxes of canopy COP, latent or sensible hea
t are less than 5% between the multi-layered model and two-leaf model.
Our results show that the two-leaf model can predict net photosynthes
is, latent and sensible heat fluxes of a canopy quite accurately under
a wide range of soil water availability and meteorological conditions
, as compared with the multi-layered model. (C) 1998 Elsevier Science
B.V. Ah rights reserved.