1. Tracer transport simulation by an icosahedral grid model Center for Climate System Research, Univ. of Tokyo Yosuke Niwa R. Imasu, M. Satoh, S. Maksyutov, T. Machida, H. Matsueda

2. NICAM Nonhydrostatic ICosahedral Atmospheric Model NICAM was first developed by Satoh (CCSR/FRCGC) and H. Tomita (FRCGC). (H. Tomita and M. Satoh, 2004, M. Satoh et al., 2007) Developed as a global cloud resolving model (GCRM). The max resolution… dx~3.5km NICAM is also used as a low-resolution Atmospheric Circulation Model (AGCM) and as a regional model (Stretch- NICAM). I used NICAM as a AGCM and modified it an on-line tracer transport model. I added new tracers and developed nudging module resolution…dx~240km

3. Realistic experiment by NICAM OLR (by H. Miura) http://www.ccsr.u-tokyo.ac.jp/~satoh/nicam/index.html dx~3.5km A 3.5km-mesh global simulation was performed using the Earth Simulator. (H. Miura et al., 2007)

4. Grids of NICAM recursively divided Horizontal grid: Vertical grid: Terrain-following coordinate: It looks like σ coordinate, but doesn’t depends on pressures and is not time-variable. Regional model version: stretched grid icosahedral grid

5. Advantages of NICAM for tracer transport simulations High-resolution if I could use the Earth Simulator Tracer masses are completely conserved without a mass fixer Tracer advection is consistent with continuity Easy to develop adjoint code no limiters or fixers, not semi-Lagrangian scheme → good properties for high-resolving inverse method. Since NICAM is a new model, evaluation of the model performance is needed.

6. The setting of NICAM Horizontal resolution: dx~240km The number of vertical layers: 54 Time step: 20 min Advection scheme : Miura2004 scheme (horizontal) 2 nd order difference (vertical) Cumulus convection : simplified prognostic Arakawa- Schubert Vertical diffusion : Mellor-Yamada 2 with modification by Smith (Smith, 1990) Analysed fields used for nudging: NCEP, JRA (not submitted to TC cont.) Meteorological variables used for nudging: U, V (τ=0.7day), T (τ=3day) Nudged only for the free troposphere (12 th layer ~) not nudged in boundary layers

7. Evaluation of meridional transport comparison with TransCom 3 models ① The North-South gradient simulated by NICAM is smaller than other models. Surface500hPa tracer : fossil fuel 1990

8. Evaluation of meridional transport comparison with TransCom 3 models ② stronger inter-hemispheric transport TransCom 3 models NICAM tracer : fossil fuel 1990

9. CTL Nudged sub-grid transport by cumulus convection was reduced by half ½ cumulus effect dynamical field simulated by NICAM is not problem cumulus convection hardly affect! Large scale advection is the cause of inter-hemispheric transport Due to the advection scheme of NICAM ?

10. SF 6 simulation TransCom 2 experiment S. Denning et al., 1999 NICAM

11. Comparison with TransCom continuous data experiment models fossil98SF6 SF 6 observation data were downloaded from WDCGG site Inter-hemispheric transport of NICAM is still seemed to be stronger NICAM observation

12. Vertical transport: 222 Rn simulation Comparison with Jacob, et al., 1997 Green: other models, Blue: NICAM (V: not nudged, X: JRA, Y: NCEP) Although there is an uncertainty of radon fluxes, the vertical transport simulated by NICAM is seemed to be a little stronger than others in summer. summer winter PBL upper airobs.

13. Comparison with continuous data at Hateruma + R Observation data were downloaded from WDCGG site DJF JJA Except in summer, high CO 2 air from continental PBL was captured well. SiB CASA blue:SiB, green:CASA, red:observation

14. Comparison with aircraft data Vertical profile @ Novosibirsk (West Siberia) Upper air by JAL airplane (Tokyo-Sydney) Boundary layer was simulated well z S ← latitude → N convected high CO2 air OLR Siberia data were provide by T. Machida (NIES) JAL data were provided by H. Matsueda (MRI) NICAM observation

15. Summary and Perspective Introduction of NICAM  NICAM is a new model developed as a global cloud resolving model.  The grids of NICAM are very different. Comparison with TransCom models  Inter-hemispheric transport simulated by NICAM is stronger than other models  The model results are in the range of other model results and in good agreement with observations. Comparison with observations  Synoptic scale variations were captured well.  Small scale variation of atmospheric CO2 were reproduced. Perspective  Development of high-resolving inverse model

16. Thank you! Acknowledgement The datasets used for this study are provided from the cooperative research project of the JRA-25 long-term reanalysis by Japan Meteorological Agency (J MA) and Central Research Institute of Electric Power Industry (CRIEPI). NCEP Reanalysis data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.cdc.noaa.gov/. Aircrafts observation data at Siberia sites were offered from T. Machida (NIES) and JAL observation data were offered from H. Matsueda (MRI).