Abstract
A class of simple zonally symmetric models of increasing complexity viz. Webster and Chou (1980a), Gadgil and Srinivasan (1990) and Srinivasan et al. (1991) have yielded increasingly realistic simulation of the intraseasonal variation of the tropical convergence zone (TCZ) over the Indian region in the summer. A new model in this class, which incorporates the space-time variation of surface pressure is discussed in this paper. As in the earlier models, the prominent feature of intraseasonal variation in the Indian region viz. poleward propagations of the TCZ is simulated. The rate of propagations in this model is more realistic and the period between propagations is also more realistic being about thirty five days. A new feature simulated by this model is the active phase of the monsoon with the TCZ persisting over the continental trough for about 20 days. The underlying mechanisms, unravelled by analysis of this and earlier models of this class are discussed in this paper.
