The results show that the propagations of the atmospheric ISO in the East Asian monsoon region in summer include zonal propagation and longitudinal propagation.

On the intraseasonal oscillation(ISO) time scale,the zonal propagation of atmospheric ISO in 2006 had its own uniqueness;the westward and stationary ISO along the latitude belt of the Yangzi River valley was weaker while the eastward and stationary ISO precipitation in Southern China.

In this paper,in order to effectively speed up the weight convergence speed of neural network,a new back-propagation algorithm is proposed.

Based on the idea of standard back-propagation(BP) learning algorithm, an improved BP learning algorithm is presented.

Next, an Improved Back Propagation(IBP)algorithm is proposed, considering the drawbacks of the standard Back Propagation (BP) in the neural network theory.

Based on this framework, by making use of the back propagation method of computing partial derivatives, the maximization of mutual information can be achieved through the gradient ascent optimization process, and thus the discriminative training of HMM is performed.

In this study,the flood hydrograph at the forecasting section of tidal reach was considered as the superposition between flood waves from upstream and tide waves from downstream after bidirectional propagation.