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(1) A carbon cycle model, a carbon cycle and a climatic change joint model subgroup

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(1) Terrestrial carbon cycle model

(2) Oceanic cycle model
(3) Dynamic vegetation model

The terrestrial biosphere absorbs atmospheric CO2 by photosynthesis, by breathing and soil organic matter decomposition of vegetation, returns CO2 to the atmosphere and bears main roles in a terrestrial carbon cycle. Between a terrestrial carbon cycle, and atmospheric composition and a climate change, various interactions, such as change of the energy balance which let CO2 concentration change, and the albedo and water loss change by net carbon balance change pass as change of the photosynthesis, breathing, and soil organic matter decomposition by the photosynthesis fertilization effect by air CO2 concentration increase and temperature variation, change of the photosynthesis and soil organic matter decomposition by water cycle change, and an action of the terrestrial -> atmosphere, are mentioned. Therefore, in order to perform more exact future prediction, the earth system integrated model which introduced the interaction of a carbon cycle needs climate and to be built.

In an earth system integrated model, the role of a terrestrial carbon cycle is important. By the result of Hadley Center and IPSL which did pioneering research in this field, prediction of a future air CO2 concentration and climate change shows a big difference in both. The difference in the response of a terrestrial carbon cycle model is mentioned to one of the factor of this. The present condition is that the result that even the marks of sink sauce differ depending on a model is obtained to a global carbon cycle. Therefore, it is necessary to also perform simultaneously improvement in accuracy of a terrestrial carbon cycle model.

This subgroup is advancing research for the purpose of two points, the improvement in accuracy of (1) terrestrial carbon cycle model, and joint 、 of (2) terrestrial carbon cycle and a general circulation model. The model of the first step is completed by combining both "Sim-CYCLE" and "MATSIRO" to whom development is given in our country in creation of a terrestrial carbon cycle model. Sim-CYCLE is a model which treats the biogeochemistry process of the seasonal variation and secular variation of a terrestrial living thing and soil from income and outgo, such as carbon and water. On the other hand, MATSIRO is a model which is developed as a land process model of GCM, simulates a canopy, radiation balance, an energy balance, a water balance in soil, etc., and treats the phenomenon of a short time scale. The water through the vegetation in terrestrial, CO2, and the integrated model about exchange with the atmosphere of energy are built in the form where MATSIRO uses LAI (leaf area index) predicted by Sim-CYCLE, and the soil temperature and soil water content predicted by MATSIRO are used by Sim-CYCLE.

FY 2003 is
    (1) Sim-CYCLE off-line evaluation
    (2) Combination of Sim-CYCLE and MATSIRO-AGCM
    (3) Inclusion examination of the carbon balance process by artificial land use change
Three points were performed.

About Sim-CYCLE off-line evaluation, analysis about the factor which brings about un-deciding [ of future prediction of a terrestrial carbon cycle ] was performed. This factor can consider four points, the uncertainty of model structure, the uncertainty of a model parameter, the uncertainty of a future climatic prediction, and the uncertainty of a future greenhouse gas delivery. Among these, it evaluated about three points, the uncertainty of a model parameter, the uncertainty of a future climatic prediction, and the uncertainty of a future greenhouse gas delivery. Consequently, changing sharply became clear by the temperature dependency parameter and the future climate scenario (it is dependent on GCM) of a decomposition process of a soil organic matter.

Moreover, in order to build the integrated model of a carbon cycle and climate, combination of CCSR/NIES GCM (included MATSIRO) and Sim-CYCLE was performed. It joined together as mentioned above through the coupler contained in GCM in the form which carries out mutual interpolation of Sim-CYCLE and the MATSIRO. By adding the transportation process of the atmosphere CO 2 to AGCM, and generating CO2 exchange in land, the seasonal variation of air CO2 concentration could be simulated and combination has been checked.

Model construction towards the participation to an international project has also been performed. About the model which unified the carbon cycle and climate like this subject, C4MIP (The Coupled Climate-Carbon Cycle Model Intercomparison Project; both carbon cycle-climate joint models comparison project) is trying to start. On the first stage of this project, it is to focus on a terrestrial carbon cycle. In order to participate in this project, it is necessary to include CO2 discharge process by land use change of converting into natural vegetation and cultivated land. In the current fiscal year, introduction of this process was considered to simple substance Sim-CYCLE.

It is necessary to advance immediately reappearance of evaluation of Sim-CYCLE and a MATSIRO joint model, and the past carbon cycle, and development and evaluation of the integrated model united with the C4MIP protocol as a future subject. Furthermore, change of the vegetation zone by earth environment change is also due to unify with the model of an ecosystem change process model subgroup, and to be included in a model from now on.


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(2) Oceanic carbon cycle model

(1) Terrestrial carbon cycle model
(3) Dynamic vegetation model

As a preceding paragraph story of carbon cycle process inclusion to an air sea joint model, the preliminary warming experiment was conducted using the carbon cycle model included in the sea simple substance model. That is, it was investigated how sea carbon-dioxide absorbed amounts when the carbon dioxide levels in the atmosphere increase according to an IS92a scenario about the case where marine environment changes with warming, and the case where that is not right would differ among both cases, using the wind stress and sea skin temperature which were obtained as a result of the carbon-dioxide gradual increase experiment conducted in the past using the air sea joint model as driving force of an oceanographic model. Consequently, the result that the influence which the ocean circulation change by warming has on a carbon-dioxide absorbed amount was small was obtained (Fig. 1). The result of having conducted the experiment even with the IPCC Third Assessment Report same at two or more models is reported, and according to it, a difference has the influence of warming by a model. However, compared with the result of having conducted the experiment which corresponds by a terrestrial carbon cycle model, the influence of the sea carbon cycle on warming is small intentionally, and every oceanographic model can be said that our result is not contradictory to the past thing at this point. The model adopted in this project finished with the warming experiment here confirming the past experimental findings, although description of a hydrographic table layer ecosystem was detailed rather than what is adopted by the IPCC Third Assessment Report. Although this very thing is not a gay result, it can be said that it has checked that our model showed the behavior which will seemingly be reasonable as a preceding paragraph story combined with a terrestrial carbon cycle.

This is received, a carbon cycle model transplant to an air sea joint model is also started, and it is in the stage which the prototype completed now (Fig. 2). From now on, tuning of a model parameter, maintenance of a code, and enough spins up are performed, and it will prepare for the participation to both the carbon cycle-climate joint models comparison project (C4MIP), as a result the contribution to the 4th IPCC report.

Fig. 1: Model prediction of sea carbon-dioxide absorbed amount when carbon dioxide levels in the atmosphere increase according to IS92a scenario. Fig. 1: Model prediction of sea carbon-dioxide absorbed amount when carbon dioxide levels in the atmosphere increase according to IS92a scenario. When there is no change of the marine environment by warming and it is presupposed by the red line that there is a black line.
Fig. 2: the earth surface by the air sea joint model incorporating carbon cycle process -- the annual carbon-dioxide flux in - sea surface.

Fig. 2: the earth surface by the air sea joint model incorporating carbon cycle process -- the annual carbon-dioxide flux in - sea surface. A unit is molC/m^2/yr. A red portion shows the place where carbon dioxide is emitted into the atmosphere, and a blue portion shows the place where carbon dioxide is removed from the atmosphere.

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(3) Dynamic vegetation model

(1) Terrestrial carbon cycle model
(2) Oceanic carbon cycle model

In the integrated model which is furthering development in the 2nd project of symbiosis, it is planning treating the ecosystem process in land by terrestrial carbon cycle model Sim-CYCLE. Sim-CYCLE assigns 18 sorts of vegetation types beforehand to each grid of land, and simulates the influence which change of climate has on the structure and the function of vegetation, and the feedback reaction which the change by the side of these vegetation gives to a climate system.

In Sim-CYCLE, it assumes that the vegetation type of each land grid is eternal. However, it feels it uneasy to enlarge such a potential error that it will become long if the period which is considered that the composition of the plant in each area also changes from 100 years gradually in the long time factor of hundreds of years, therefore simulates this assumption becomes long. So, in this subgroup, the constituent factor which predicts vegetation change is added to Sim-CYCLE, and it extends to all the so-called ball dynamic vegetation models (Dynamic Global Vegetation Model, DGVM).

In order for change of climatic conditions to simulate change of vegetation composition, and the effect which can be given to the speed, it is necessary to extend about the following four points at the lowest.

  • terrestrial vegetation is expressed as a vegetality type (Plant Functional Types, PFT) assortment.
  • Dynamic processes, such as death and fixing, are defined as a function of an environmental condition.
  • The disturbance process of a fire etc. in which it has had big influence on the vegetation dynamic state is incorporated.
  • The struggle for existence between PFT(s) or between individuals is incorporated clearly, and change of the composition of PFT and prediction of the period which it takes are enabled.
In this subgroup, in addition to the above extension, an arbor is treated with an individual base and the ambitious trial in which the space structure of a stand is taken in further clearly is performed. The direction of vegetation change and prediction of the period which it takes are expected to be obtained more appropriately by these. The competition for the plant which is a sticking tendency is because it is thought that that it is strongly specified to a very local environmental condition, and such locality is disregarded will change the direction of vegetation change and prediction of speed a lot.
The program which will simulate vegetation change of only one point by the present was completed. The ground of performing the simulation in a total ball level was prepared after the parameter estimation and adjustment which will be performed from now on, and work called vectorization.


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