摘要
An ocean-atmosphere and land-air coupled numerical model system is used to study the basic properties and the monthly time variations of the summer quasi-stationary circulation systems. It is found that either at the upper or at the lower levels of the atmosphere, the circulation patterns have a two-wave structure in the zonal direction at the mid and high latitudes of the Northern Hemisphere. Such a structure of circulation is totally matchable to that of the land-sea distribution there. It is proved, hence, that the land-sea distributive pattern is the fundamental cause for the summer quasi-stationary circulation pattern. The topography in the globe is the secondary factor for circulation systems. The circulation centres of the quasi-stationary systems are always located in certain areas due to the thermodynamic contrast between land and sea.From the time evolutions of the circulation systems it is seen that the change is larger at the beginning period of the time integration, it is because of using the zonally averaged mean fields as the initial values of the model. As long as the basic simulated pattern of circulations reaches the state similar to that of the real climatic fields resulting from the coeffects of the land-sea distribution and the topography, the circulation systems modelled will change slowly and tend to a quasi-stationary state. Therefore, the time integration does not need to last for a very long time, if the purpose of numerical modellings is to test sensitivities of some factors influencing the climate, 20 model days may be enough for sensitive experiments.
An ocean-atmosphere and land-air coupled numerical model system is used to study the basic properties and the monthly time variations of the summer quasi-stationary circulation systems. It is found that either at the upper or at the lower levels of the atmosphere, the circulation patterns have a two-wave structure in the zonal direction at the mid and high latitudes of the Northern Hemisphere. Such a structure of circulation is totally matchable to that of the land-sea distribution there. It is proved, hence, that the land-sea distributive pattern is the fundamental cause for the summer quasi-stationary circulation pattern. The topography in the globe is the secondary factor for circulation systems. The circulation centres of the quasi-stationary systems are always located in certain areas due to the thermodynamic contrast between land and sea.From the time evolutions of the circulation systems it is seen that the change is larger at the beginning period of the time integration, it is because of using the zonally averaged mean fields as the initial values of the model. As long as the basic simulated pattern of circulations reaches the state similar to that of the real climatic fields resulting from the coeffects of the land-sea distribution and the topography, the circulation systems modelled will change slowly and tend to a quasi-stationary state. Therefore, the time integration does not need to last for a very long time, if the purpose of numerical modellings is to test sensitivities of some factors influencing the climate, 20 model days may be enough for sensitive experiments.
基金
Supported by National Fundamental Key Research Project:"Studies on dynamic climate and climate prediction theory".
