Based on the theory of chaotic dynamics for nonlinear systems,and according to the yearly drought and flood level data within 1624 a(from 380～2003) in Xi’an area,a study on the chaotic characteristics and the predictability of the climatological system were investigated by calculating the associated dimension,Kolmogorov entropy and Lyapunov index of climatological attractor.

From the analyses,we can draw some conclusions as follows:(1)There existed some primary periods in the changes of the dryness and wetness in Guangdong from the viewpoint of the historical course,such as 7 years,15 years and 23 years and so on.

The characteristics of the interdecadal variations of drought and flooding disasters in China are analyzed by using the observed data.

Study on influence of arid climate change to drought disaster in Gansu and technique of preventing drought and reducing disaster;

It is found that the main features of arid climate change is that precipitation decreased obviously in the 1990s and aridity took place in the north,mainly in Hebei,Shanxi,Shandong provinces and the east part of Northwest.