A coupled model of land surface CO 2 and energy fluxes using remote sensing data

Abstract

Considering the coupling of plant transpiration with plant photosynthesis through stomatal opening, this paper develops a dual-source model that simulates the energy and CO 2 fluxes between a vegetated land surface and the lower atmosphere. Two versions of the CO 2-energy coupled model (CECM) are presented. The version CECM SM uses daily surface soil moisture measurements or estimates along with meteorological variables and vegetation parameters as inputs. The other version CECM Tr utilizes remotely sensed radiometric surface temperature instead of surface soil moisture estimates. The two versions of the model are evaluated by comparing their predictions of CO 2 ( F c), latent heat ( LE) and sensible heat ( H) fluxes and surface temperature ( T sf) with three datasets collected from two large-scale field experiments (FIFE’87 and Monsoon’90), which were conducted over two different types of land surface. For the three datasets, the correlation coefficients between the predictions of H, LE and T sf from both versions of CECM and their observations ranged from 0.77 to 0.97. The F c predictions from CECM SM had a correlation of 0.96 and a 16% mean absolute percent difference (MAPD) with the observations. For both CECM SM and CECM Tr the agreement with measured LE was generally better than H where MAPD values ranged from 15–35 to 20–55%, respectively. The values of some parameters in the stomatal conductance and leaf photosynthesis models obtained in the literature for general C 3 plants in the temperate areas were found inappropriate for the C 3 shrubs at the site of the Monsoon’90 experiment which have adapted to the semiarid environment. After these parameters were adjusted to give similar stomatal resistance from other work, the LE and H predictions from CECM were improved.