Material transports associated with large-scale waves and their seasonal and interannual variations

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Nonlinear behaviors of large-scale atmospheric waves in the troposphere and the stratosphere were investigated with a hierarchy of numerical models, which we have been developed and used. Material transport processes associated with these waves were also studied with some tracer models. Seasonal dependence, interannual variations, and trends of the wave behaviors were also clarified by analyzing long records of numerical time-integrations and global observation data.1. Model development : A numerical library to solve geophysical fluid motions in some typical geometries efficiently in supercomputers has been developed. As application tests of the models, 2-D decaying turbulence on a rotating sphere and gravity wave radiation in a rotating shallow water system are investigated.2. Planetary waves : A global circulation model with simplified physical processes was used to investigate the effects of the equatorial QBO winds on planetary waves and mean meridional circulation in the winter he … More misphere. It was demonstrated that large sample method based on long enough data is a powerful tool to show the statistical significance of the QBO effects. In order to study horizontal mixing and transport barrier in winter stratosphere, assimilated data for 9 years from 1990 were used to do local Lyapunov stability analysis and compute Lagrange trajectories of many particles. Interannual variations of the mixing were quantified with these analyzes.3. Baroclinic waves : Long time integrations of an atmospheric GCM were done with an idealized SST to investigate the dynamics of localized storm tracks. It was found that the most important factor to determine the localization is nonzonal (west-east) component of the meridional gradient of SST in mid-latitudes.4. Equatorial gravity waves : Generation, propagation and breaking processes of convectively generated gravity waves were firstly simulated with a meso-scale non-hydrostatic numerical model from the surface to the lower thermosphere (about 100 km height). An estimation method of convectively generated waves in the equatorial region based on satellite observations of IR radiation was developed and tested. Less