Development of a global cloud resolving model - a multi-scale structure of tropical convections -

We have developed a global cloud resolving model, that is a new high resolution atmospheric gen- eral circulation model. It is a grid model with icosahedral structure and is based on the non-hydrostatic equa- tions. The new model is called Nonhydrostatic ICosahedral Atmospheric Model (NICAM). At present, the first version of the model is almost completed. We evaluated the model performance by several test cases on the Earth Simulator, and found a very good computational efficiency. The main target is high-resolution climate simulations by improving representation of cumulus convec- tion with resolutions less than 5 km in horizontal directions. The global cloud resolving approach enables us to avoid use of cumulus parameterization that is one of the most ambiguous components of current climate modeling. We have performed global cloud-resolving simulations with super-high resolutions on an aqua planet setup using NICAM. We studied the resolution dependency of the results and found that the simulations with grid intervals of 7 km and 3.5 km well capture hierarchical structure of clouds from cloud resolving scale to global scale. These successful results suggest that the global cloud-resolving simulation becomes one of promising approaches in the climate research field in the near future.

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