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Title: A MODEL FOR STOMATAL CANOPY CONDUCTANCE COUPLED WITH CLASS-A CANADIAN LAND SURFACE SCHEME FOR GCM'S

Author
item MANUNTA, P - UNIVERSITY OF ALBERTA
item GRANT, R - UNIVERSITY OF ALBERTA
item VERSEGHY, D - CANADIAN CLIMATE CENTER
item Kimball, Bruce

Submitted to: American Meteorological Society
Publication Type: Proceedings
Publication Acceptance Date: 1/28/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: In order to predict accurately the consequences of present and future global environmental changes on the security of world food production and on future irrigation requirements, efforts are underway to improve the general circulation models (GCMs) that are used to predict climate change. These GCMs have predicted that increasing atmospheric CO2 will cause the earth to warm and that precipitation patterns will change. However, elevated CO2 is also known to alter the growth of plants and may affect their exchange of energy and water with the atmosphere, and these vegetation changes could feedback and affect the future climate. Accordingly, to improve the land-atmosphere interface simulation, another computer model called CLASS (Canadian Land Surface Scheme) was developed to predict the effects of elevated CO2 on vegetation water and energy exchange. This paper describes a specific validation test of the CLASS model comparing its predictions with actual data from a free-air CO2-enrichment experiment (conducted in an open field) on wheat at CO2 concentrations of 550 ppm and present-day ambient of about 370 ppm. The results showed that the model could track the temperature of the crop hour-by-hour reasonably well, as well as the rates of flow of energy and water vapor. Consistent with the data, future wheat water requirements may decrease slightly, perhaps 4%, if climate warming is minimal. This work should help future growers develop optimum management strategies and, of course, should ultimately benefit all future food consumers.

Technical Abstract: Canopy stomatal conductance plays an important role in controlling the energy and mass exchange between terrestrial ecosystem and the atmosphere. However, the stomatal conductance g, of single leaves and for the whole canopy is often represented in mathematical models of these ecosystems as an empirical function of environmental factors. Such a non-mechanistic representation of conductance may cause inaccuracies in the partitioning of the energy balance components. Thus the overall performance of an ecosystem simulation model may be inaccurate. Here we describe a stomatal conductance model as part of the land surface model CLASS (Canadian Land Surface Scheme) which can run in stand alone mode or be coupled with the Canadian Climate Center GCM.