Typhoon vortices self-organization in a baroclinic environment.

A study is made for typhoon vortices self-organization in a baroclinic environment based on eight groups of numerical experiments with the fifth generation PSU/NCAR mesoscale numerical model MM5(V3) in this paper. The main results show that: in Experiment 1, there are only two separated meso-scale axisymmetric vortices with a radius 500km, and the distance between the two separated meso-scale axisymmetric vortices is 400km in the initial relative vorticity field. With the increase of model integration time, the two separated meso-scale axisymmetric vortices in initial field mutually exclude each other during the co-rotation, that is to say, the distance between the two initial axisymmetric vortices increases with the model integration time increasing. And finally, the two initial vortices exclude each other to an extent that the distance between them is greater than a critical distance, i.e. co-rotating critical distance, and the two vortices stop to co-rotate. In Experiment 2, there are a small vortex with a radius 80km between two meso-scale axisymmetric vortices in the initial field and the other initial conditions are kept the same with Experiment1. This dynamic system contains the interactions between vortices of the same and different scales. The two initially separated meso-scale axisymmetric vortices approach each other during their co-rotation, and self-organize into a typhoon-like/larger-scale vortex consisting of an inner core and spiral bands. This result supports both Zhou Xiuji’s point of view in 1994 and the research results of this kind of previous studies in a barotropic framework. Experiments 3-8 are the sensitive experiments of initial vortex parameters based on Experiments 1and 2. Among them, the effect of different initial positions of the small scale vortex on the typhoon vortex self-organization is tested in Experiments 3 and 4, and the influences of the distance and intensities of the initially axisymmetric binary meso-scale vortices are examined in Experiments 5 and 6, and 7 and 8, respectively. The results suggest that among all those initial vortex parameters, the distance between the initial axisymmetric meso-scale vortices is the most important parameter that influences the self-organizing process of the final typhoon-like vortex most. This conclusion is similar with the result of corresponding barotropical model experiments.