(2) Subject 2: Development of Integrated Earth System Model for Global Warming Prediction

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1 d. Evaluation of the High-Resolution Atmospheric model An AMIP-type run (with the observed SST for ) and a time-slice 2xCO2 run (with the same observed SST plus distribution of SST change due to 2xCO2 estimated by a lower-resolution coupled model) of the atmospheric model have been performed and analyzed. A good reproducibility of daily precipitation intensity, tropical cyclones and convective activity coupled with equatorial waves are confirmed. An enhancement of intense precipitation in a 2xCO2 climate is projected. It is also shown that some suppression mechanism of cumulus convection plays an important role in representing realistic intensity of precipitation. e. Analysis of the Hawaiian Lee Counter Current in the coupled model The Hawaiian Lee Counter Current (HLCC) is clearly found in the model. It is analyzed as a good example of phenomena unique to a high-resolution coupled ocean-atmosphere model. When the mountains over the Hawaiian Islands are removed in the model as a sensitivity experiment, HLCC disappears. It suggests that the atmospheric response to the mountains is necessary to maintain HLCC. Figure 1: Global mean 2 m temperature (upper) and hemispheric mean sea ice cover (lower) in the zeroorder control and climate change (1%/year CO2 increase) runs. (2) Subject 2: Development of Integrated Earth System Model for Global Warming Prediction Person in Charge: T. Matsuno a. Development of a Coupled Carbon Cycle - Climate Change Model a 1. Terrestrial Carbon Cycle Model Members: A. Itoh, I. Ichii, T. Oikawa, K. Tanaka The objective of this group is to develop a model that estimates carbon budget of terrestrial ecosystem, which may exert short- to long-term effects on atmospheric carbon dioxide concentration. This model will be built in the integrated earth system model and should allow us to predict the global climate change induced by the anthropogenic greenhouse effect gases. In the fiscal year 2003, this group has conducted (1) the offline assessments of the Sim-CYCLE, (2) the builtin of the terrestrial model to the AGCM, (3) the functional expansion of the Sim-CYCLE for the participation to the integrated model intercomparison project. (i) The Offline Assessments of the Sim-CYCLE To investigate the response of terrestrial carbon budget to the future climate change, the offline simulations was performed, in which the Sim-CYCLE was forced by several climate scenarios derived from GCM simulations. Based on the SRES A2 and B2 scenarios, in which atmospheric CO2 concentration was prescribed from 2000 to 2100, the offline model runs were driven without carbon-cycle feedback. The results showed that plant biomass and soil carbon increased gradually in any GCM-scenario sets in the 20th century, however in the 21st century, terrestrial carbon responded significantly to global environmental change, with remarkable differences among the climate scenarios. Additionally in more detailed analysis, these differences were founded to be originated by the differences in the temperature input data, derived from the climate models. This study showed that the uncertainties in the climate projections, which were generated by the GCMs, influenced significantly the response of soil decomposition and carbon storage. This study also presented the responsiveness of soil carbon to the prescribed environmental change, but it may also be implicative for studies with models that couple the carbon cycle and climate. 49

2 (ii) The Built-in of the Terrestrial Model to the AGCM To integrate the terrestrial carbon cycle and the climate system, the Sim-CYCLE is combined with the CCSR/ NIES GCM (including MATSIRO). Through the coupler to the MATSIRO, the Sim-CYCLE exchanges the leaf-area index (LAI), soil water content and soil temperature data with the AGCM. Translation of the C language of the Sim-CYCLE code into the Formula Translator (FORTRAN) language has been already accomplished. Now this group is carrying out the attachment of the Sim-CYCLE to MATSIRO-AGCM in co-operation with the Integrated Modeling Research Program of FRSGC. Figure 1 shows the carbon dynamics of the global terrestrial ecosystem in the preliminary simulations with Sim-CYCLE-MATSIRO-AGCM coupled model. Simulations are conducted in the integrated model run, after the 2,000 years spin-up of the Sim-CYCLE run. Net Ecosystem Production (NEP) showed adequate seasonal changes consistently with the GCM climate fields (Figure 1a). Applying the land surface CO2 budgets in the wind fields derived from the GCM outputs, atmospheric CO2 concentrations present reasonable seasonal changes in the north hemisphere; summer increasing and winter decreasing (Figure 1b). (iii) The Functional Expansion of the Sim-CYCLE for the Participation to the Integrated Model Intercomparison Project Interactions between climate and the carbon cycle have the potential to provide major feedbacks on climate change, but major uncertainties in the magnitude of these feedbacks persists. Several climate research institutes of the foreign countries promote the Coupled Climate-carbon Cycle Model Intercomparison Project (C 4 MIP) that aims to investigate the plausible sensitivity range of the climate-carbon cycle system by using a number of independent models driven by a common set of forcings. To join in the C 4 MIP, the Sim-CYCLE is required for the installation of the land use change components according to the guideline (Grand Slam Protocol; Houghton, 1983). In that protocol, as the land use changing from natural vegetation to crop land, vegetation biomass are eliminated from there and distributed to three pools that keep carbon stocks for 1, 10 and 100 years respectively. As the crop land is abandoned, natural vegetation will recover. This group now proceeds the cording operation for that installation. In the next fiscal year, this group will promote: 1) the validation of the Sim-CYCLE with the field and satellite measurement data for improving the parameterization in co-operation with the Subject 3 of the Project for Sustainable Coexistence of Human, nature, and Earth (Kyosei Project), sponsored by the MEXT, Japan and the Subject 1 of the project sponsored by the Global Environment Research Fund of the Ministry of the Environment, Japan, 2) the interface maintenance and the validation of the integrated model for improving the affinity between Sim-CYCLE and MATSIRO-AGCM, and 3) the development and simulation runs of the integrated model for the C 4 MIP. Figure 1: Carbon dynamics of the global terrestrial ecosystem in the preliminary simulations with Sim- CYCLE-MATSIRO-AGCM coupled model in (a) net ecosystem production (NEP) and (b) Atmospheric CO2. Simulations are conducted in the integrated model run, after the 2,000 years spin-up of the Sim-CYCLE run. Data are shown for the initial three years of the simulations. 50

3 a 2. Development of an Oceanic Carbon Cycle Model a-3. Dynamical Global Vegetation Model Members: H. Satoh, A. Itoh, T. Kohyama Members: M. Kawamiya, M. Aita, C. Yoshikawa, Y. Yamanaka, M. Kishi Precedent to the inclusion of the carbon cycle to our coupled climate model, a preliminary experiment for future uptake of CO2 by the ocean is carried out using an ocean-only model with carbon cycle processes. The model is forced with and without the effect of global warming using results from a coupled climate model. The CO2 concentration is increased in both cases by 1% per year after The focus is on the differences in time evolution of the uptake between the two cases, which turn out to be small (Figure 2). The present result is not something that attracts many people s attention in that it only confirms the result of past experiments reported in the IPCC Third Assessment Report, but it is meaningful for the project in that it assures that the model shows a plausible behavior. Following the experiment with the ocean-only model, we have embarked on the incorporation of oceanic and terrestrial carbon cycle processes into our coupled climate model. A prototype of a coupled carbon cycle climate model is now completed. Parameter tuning, code tidying, and sufficient spin-up etc. will be further conducted to prepare for the C4MIP and contribution to the IPCC Forth Assessment Report. While climate condition can strongly influence terrestrial ecosystem, it can also affect the climate, particularly through changes in evapotranspiration, carbon cycle, and albedo. Thus, for providing reliable predictions for the change of global climate, integrated t e r re s t r i a l e c o s y s t e m m o d e l s t h a t i n c l u d e biogeochemical processes and vegetation dynamics would be required. To fulfill this need, we are developing a Dynamic Global Vegetation Model (DGVM) that can simulate changes in ecosystem functions (ex: carbon and water flux) as well as ecosystem structures (ex: distribution and composition). This model links several modules, which have different computation time steps. Some of the modules are functions of environmental factors, letting the model simulate ecosystem responses according to environmental changes. Because spatial hetero-structure plays a central role in vegetation dynamics, this model explicitly treat forest 3D structure using individual-basis modeling approach (Figure 3). Simulation will be conducted on the T42 global grid (128*64), each of which includes 10 replication forest stands. Thus, assuming 1/3 of the earth surface is terrene, about 27,000 independent forest stands will be independently simulated. To date, this would be the most complex ecosystem model that have ever made. It should be noted that the vast computation power of the Earth Simulator capacitates this project. By 2003 fiscal year, coding of one-point simulator was almost completed. We are currently estimating parameters through test running of the program. After vectorize, parallelize, and tuning, we will conduct simulation experiment on global grid within fiscal year Figure 2: Model projection of future CO2 uptake by the ocean under CO2 increase of 1% per year after The red line represents the result where the model is forced without the effect of global warming, and the black line with it. Figure 3: A snap shot of the simulated forest stand (30m*30m of template mixed-forest). Individual tree is composed of crown, stem, and root. Shape of crown and stem are approximated by cylinder. Simulation will be conducted on the T42 global grid (128*64), each of which contains 10 replication forests stands. 51

4 52 b. Development of a Coupled Atmospheric Composition Climate Change Model b-1. Development of a Coupled Atmospheric Chemistry Climate Change Model Members: M. Takigawa, S. Watanabe, K. Sudo, T. Nagashima (NIES), T. Takemura (Kyusyu University) The subgroup of coupled atmospheric compositionclimate model aims at simulation and prediction of atmospheric chemistry(involving tropospheric/ stratospheric ozone) and aerosol processes and their interaction with climate change and ecosystem change in the framework of the FRSGC integrated model named Kyosei Integrated Synergized System Model for the Earth (KISSME). This fiscal year, we started developing a chemistry-aerosol coupled climate model on the Earth Simulator using a global chemistry model CHASER (Sudo et al., 2002) and aerosol model, SPRINTARS (Takemura et al., 2000) which are both based on the CCSR/NIES AGCM. Since the chemistry component in CHASER, including 53 chemical species and 140 photochemical reactions in its present configuration, requires much computational time relative to the default AGCM, optimization of the CHASER code is also our critical issue in view of our planed long-term simulations on the Earth Simulator. This fiscal year we tuned the code of the CHASER chemistry component prior to coupling the aerosol component of SPRINTARS with CHASER. Owing to our tuning, the total Central Processing Unit (CPU) time required for the all processes in CHASER (including dynamics and physics) decreases by 35% on the Earth Simulator. We have also performed future simulations of tropospheric ozone with CHASER, focusing on the impacts of future climate change on tropospheric chemistry. Our simulations show that future tropospheric ozone distributions and budgets can be modulated significantly by climate change influences such as water vapor increases and large scale atmospheric circulation changes. In addition, we have evaluated the transport process (especially in the stratosphere this fiscal year) in the CCSR/NIES AGCM. We calculated distribution of age of air, a good measure of cross-tropopause and stratospheric transport, and evaluated it with the observation derived age distribution. The observed air age is well reproduced by the model in the tropics, but is underestimated in the extra-tropics. b-2. Global Warming Precise Assessment of Feedback between Cloud, Aerosol Particles and Radiation Members: N. Kuba, T. Suzuki, T. Nozawa(NIES), Y. Tsushima, K. Suzuki, T. Nakajima The assignment of this group is to develop the parameterization estimating the indirect radiative forcing of aerosol particles for GCM. Two kinds of parameterization (Abdul-Razzak et al., 1998 and Kuba, 2003) to predict the number of cloud droplets are installed to the CCSR/NIES/FRSGC AGCM with SPRINTARS (Takemura et al., 2000, 2002). The global distributions of annual mean of cloud droplet effective radius are compared between model results and satellite data. The lack of knowledge about the performance of organic carbon particles as cloud condensation nuclei (CCN) leads to the underestimation of cloud droplet number. To improve the parameterization, the cloud resolving global/ regional model is needed. To develop the cloud resolving global model, cloud microphysical model (bulk method) and radiation model (MSTRNX) are installed to Nonhydrostatic ICosahedral Atmospheric Model (NICAM). Besides, to develop the cloud resolving regional model, cloud microphysical model (2 moment bin method) is being installed to Cloud Resolving Storm Simulator (CReSS). c. Development of a Cryospheric Climate System Model Sub- group of Crysophere modeling Members: A. Abe-Ouchi (FRSGC/Universityof Tokyo) Co-workers: F. Saito (University of Tokyo), T. Segawa, R. Ohgaito, T. Ogura (NIES), H. Hasumi (University of Tokyo) In order to investigate the influence of global warming upon the cryosphere, such as ice sheet and sea ice this group has worked on 1) an ice sheet model called Ice Sheet Model for Integrated Earth System Studies (ICIES), (Saito and Abe-Ouchi, 2004) and 2) a GCM which is a coupled ocean-atmosphere-seaice model called MIROC, developed cooperatively with Kyosei- 1 and been running on the Earth Simulator. The ice sheet model, which is forced by temperature and precipitation was applied to the two major ice sheets, Antarctica and Greenland ice sheet. It has a resolution of 20 km to 40 km and successfully simulates the modern shape, flow and temperature of both ice sheets. The GCM which has a resolution of 2.8º latitudelongitude for atmosphere and 1 to 0.5º for ocean part, was used to estimate the change of temperature and precipitation over these polar regions as well as the sea ice distribution and it was forced with 1% per year compound CO2 increase for 140 years followed with constant CO2 level which is 4 times of present level (1380 ppm). It is shown that over Greenland, temperature increase due to doubling of CO2 and quadrupling CO2 were 4 and 8 ºC, respectively and they already cross the threshold that more than half of the ice sheet melts down after several hundred years. Over Antarctica, on the other hand, precipitation increase seems to cancel out or overcome the melting due to the warming. Since the result must be dependent on the climate sensitivity of GCM and also the expression of the North Atlantic Deep Water (NADW), we will repeat the analysis with other versions of our GCM which is now under investigation and also run our ice sheet model with the outputs of GCM as the next step. Also the work to couple directly the ice sheet model to GCM is in progress.

5 d. Improvement of the Physical Climate System Model Members: S. Watanabe, S. Emori, T. Nagashima (NIES), T. Suzuki, T. Suzuki, K. Takata, T. Matsuno, M. Kimoto (University of Tokyo), H. Hasumi (University of Tokyo) This sub-group aims at improvement of an AGCM used as a basic component of the Integrated Model. The AGCM is based on the CCSR/NIES/FRSGC AGCM version 5.7b, which has been developed for the IPCC assessments, i.e., a main objective of Subject 1 of the Kyosei Project. In order to predict long-term changes in chemical composition, e.g., stratospheric ozone, the model has been extended to include the middle atmosphere (up to about 80 km). There has been a prominent shortcoming in the previous version of the AGCM. Temperatures near the tropopause had a large cooling bias by about 10 km, so that distribution of moisture and clouds was quite unrealistic. In order to look for causes of such biases, Mini-Project for Physical Process Intercomparison (MIPPI) was conducted as a cooperative effort with Japan Meteorological Agency (JMA) and UK Hadley Centre. As a result, it was found that radiative heating rate near the tropopause was significantly underestimated in the previous version of our radiative transfer code mstrn-8 (see Nakajiama et al. 1995). Very recently, a new version of radiation code mstrn- X was released by CCSR radiation group (please refer Ph.d thesis for University of Tokyo; Sekiguchi 2004), in which following improvements were made; 1) an update of High Resolution Transmission Melecular Absorption (HITRAN) database for atmospheric absorption, 2) a replace of a program calculating continuum absorption (from LOWTRAN7 to MT_CKD_1), 3) a substantial increase of bands for calculations of atmospheric absorption, 4) a change in optimization method for a selection of integration points. The cooling biases near the tropopause and in the lower stratosphere are significantly reduced when the new radiation code is used (Figure 4). It is also found that appropriate tuning of orographic gravity wave drag parameterization is important to improve the temperature fields near the tropopause. Other efforts performed in this fiscal year are an implement of a non-orographic gravity wave drag parameterization and an estimation of gravity wave source distribution by using a very high resolution version of the AGCM. The non-orographic gravity wave drag parameterization is required for a better simulation of the middle atmosphere, because it represents effects of unresolved waves which accelerate/decelerate large-scale wind fields. A Doppler-spread parameterization proposed by Hines (1997) is employed, because it has been well tested by various modeling groups. Global distribution of horizontal root mean square (RMS) winds associated with small-scale (horizontal wave length: km) gravity waves are obtained from a T213L250 AGCM simulation. The RMS winds and propagation directions are derived using a hodographic method around 70 hpa, and averaged over a month. Realistic characteristics of gravity waves are realized; 1) large wind variances and a dominance of westward propagation over storm tracks, and some localized maxima over mountainous regions in mid latitudes of winter hemisphere, 2) broad maxima corresponding to large-scale precipitation patterns in the tropics and mid latitudes of summer hemisphere, which reflect importance of source distribution, 3) minima in high latitudes of both hemispheres. By use of this source information with the Hines parameterization, realistic circulations in the tropics are realized with a middle resolution version (T42L78) of the model (not shown). Figure 4: Zonal mean temperature biases [K]. T106L56 simulation using mstrn-8 (a), and mstrn-x without orographic gravity wave drag parameterization (b). See text. 53