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TitleThe Coupling of a Three-dimensional Regional Atmospheric Model to a Biospheric CO2 Flux Model
AuthorChan, D; Liu, J; Yuen, K; Higuchi, K; Chen, J M; Cihlar, J
SourceInternational Science Conference: The Role of Boreal Forests and Forestry in the Global Carbon Budge, Edmonton, Alberta, Canada, 8-12 May; 2000.
Alt SeriesEarth Sciences Sector, Contribution Series 20042856
AbstractOver the last 150 years, various anthropogenic activities have significantly increased the level of greenhouse gases in the atmosphere. Specifically, the atmospheric CO2 concentration has risen exponentially since the mid-18th century, with a current globally averaged growth rate of about 1.4 ppmv/year. On average, about 40 to 45% of anthropogenic CO2 emissions from the burning of fossil fuels and deforestation activities appears to stay in the atmosphere. There is great scientific interest in determining the allocation of the remainder and the processes involved, as understanding these processes may lead to useful predictions of future CO2 concentrations in the atmosphere.

The main reservoirs of CO2 on daily to decadal time scales are the atmosphere, the land biosphere and the oceans. The fate of the anthropogenic CO2 is determined by the exchange processes among these major reservoirs. To study the exchange processes and their governing factors between the land biosphere and the atmosphere on daily to annual time scales, and on the mesoscale space scale, we are coupling a mesoscale atmospheric model to a mesoscale (landscape scale) biospheric CO2 flux model.

The atmospheric model is the Mesoscale Compressible Community (MC2) model (Benoit et al., 1997). The MC2 model is a full-elastic non-hydrostatic model; it solves a full set of Euler equations on a limited area domain with time-dependent nesting of the lateral boundary conditions supplied by a large-scale model. The nesting capability of MC2 allows the study of processes over a wide spectrum of scales.

The biospheric CO2 flux model is the Boreal Ecosystem Productivity Simulator (BEPS) (Liu et al., 1997). BEPS is a process model using the principles of FOREST biogeochemical cycles (FOREST-BGC) (Running and Couglan, 1988) for quantifying the biophysical processes governing ecosystems productivity, but with modifications to better represent canopy radiation processes (Liu et al., 1997) and canopy photosynthesis (Chen et al., 1999). The processed remote sensing data required by the model are the leaf area index (LAI) (10-day interval) and land cover type (annual). The meteorological data include hourly air temperature, incoming shortwave radiation, precipitation and humidity. The soil-data input is the available water-holding capacity.

In this paper, we will discuss the modifications to these models and compare the results of these models to the observation obtained at a mixed boreal forest CO2 monitoring site at Fraserdale in northern Ontario. We will also discuss the feasibility of quantifying regional forest carbon sinks using the diurnal and seasonal variability of atmospheric CO2 concentration, in combination with discrete isotope and planetary boundary layer profile measurements.


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