摘要
Large vortices with scales ranging from hundreds meters to tens of kilometers are generally found in the atmospheric convective boundary layer(CBL). These vortices play important roles in the vertical transport of momentum,heat,water vapor and other tracers in the boundary layer.On the basis of the view of interaction between the convection in CBL and the gravity waves in the upper stable layer the authors developed a convection-wave theory on the formation of large vortices.According to the theory the wavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in both of the upper and lower layers,such as wind speed,wind direction shear,stratification as well as temperature jump. In the present paper satellite image and weather data in a case of cold air outbreak over warm ocean are analyzed to study every stage of the convective processes,such as cloud street, convective cell as well as their transformation.According to the theory the wavenumber compositions for cloud street and convective cell are calculated,respectively,on the basis of the atmospheric conditions at every stage.The distributions of vertical motions,convergent band and disturbed interface are obtained and compared with the cloud patterns in the convective processes. Thus the study seems to offer a likely explanation for the origin of large vortices in CBL.
Large vortices with scales ranging from hundreds meters to tens of kilometers are generally found in the atmospheric convective boundary layer(CBL). These vortices play important roles in the vertical transport of momentum,heat,water vapor and other tracers in the boundary layer.On the basis of the view of interaction between the convection in CBL and the gravity waves in the upper stable layer the authors developed a convection-wave theory on the formation of large vortices.According to the theory the wavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in both of the upper and lower layers,such as wind speed,wind direction shear,stratification as well as temperature jump. In the present paper satellite image and weather data in a case of cold air outbreak over warm ocean are analyzed to study every stage of the convective processes,such as cloud street, convective cell as well as their transformation.According to the theory the wavenumber compositions for cloud street and convective cell are calculated,respectively,on the basis of the atmospheric conditions at every stage.The distributions of vertical motions,convergent band and disturbed interface are obtained and compared with the cloud patterns in the convective processes. Thus the study seems to offer a likely explanation for the origin of large vortices in CBL.
基金
This research was supported by the National Natural Science Foundation of China
