EFFECTS OF THE AMBIENT TEMPERATURE GRADIENT ON DEVELOPMENT AND MOVEMENT OF TROPICAL DISTURBANCES

The effects of the ambient temperature gradient on the development and movement of tropical disturbances have been analysed through a two-layer model of the CISK.The results show that when the gradient exists in the external area of disturbances and directs to their center,it is favourable to the development of disturbances,but an unfavourable case occurs when the gradient exists not only in the external but also in the internal areas of the disturbances.It is also shown that the gradient makes the disturbances tend to move toward warm environments.These results coincide with the observational facts which take place when cold fronts approach typhoons or tropical cyclones.