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Large-scale simulation by the cloud-resolving model

Large-scale simulation by the cloud-resolving model Large-scale weather simulation has been performed on Earth Simulator(ES). In general, the weather model is divided roughly into two types, 1) a global model which computes a whole area of the earth (general circulation model: GCM), and 2) a regional model by which a limited area is calculated in detail. A global model employs hydrostatic approximation and cloud physical processes that consume a large amount of machine resources are parameterized. On the other hand, in a regional model, cloud physical processes are explicitly expressed without parameterizations in detail and non-hydrostatic equations are used for a dynamical process of the atmosphere. In the pre-ES era, the computation area of a regional model was several million square km at most because of the limitation of machine resources. Earth Simulator has broken this limitation and made it possible to simulate the weather of the whole globe.
In our this research, the computation area is the tropical and subtropical regions between 45°South/North around the whole globe from 45° to 45° as shown in Figure 1. The horizontal resolution is 5km, and 35 layers are taken in the vertical up to 35 km. Such a wide-area high-resolution simulation by a regional model that requires huge machine power scarcely exists in the world. The following figures are results of after ten days integration of an aqua planet. Figure 2 is a snap shot of precipitation. Equatorial precipitation observed by a weather satellite is successfully reproduced.
Fig.2(left)  Fig.3(right)
The pressure and the velocity of a part of the tropical area are shown in Figure 3. Figure 4 shows zonal mean horizontal mass flux. The mass flux to the high latitude at the tropopause (12-13) km corresponds to the Hadley circulation that was able to be reproduced by the conventional general circulation model. On the other hand, the mass flux to the high latitude at the middle troposphere (5-6 km) has been clarified by a detailed observation of a tropical region only in recent years, and the phenomenon was not clearly reproduced in the simulation of the past.
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  • Tohoku Univ. 1982-1989
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