7.1　Characteristics of DHR Model

The main features of the DHR model are the representation of trends and periodic components.The change of ozone content in the atmosphere is consistent with the time series analyzed by DHR.

On the one hand,as a result of human activities,the atmospheric ozone content in the long term there will be a significant trend of change.People to the atmosphere emissions of various gases such as：NO,OClO,etc.,making the ozone content of the atmosphere showing a decreasing trend in the annual rate of change is particularly evident.Then,people began to realize that the ozone layer on human survival and development significance.In the Montreal Protocol,people began to limit the emissions of pollutants,so the atmospheric ozone content of decreasing trend slowed down in recent years,the observation of the ozone content in the atmosphere has a gradual increasing trend.

On the other hand,another important reason for the change in ozone levels in the atmosphere is the activity of the sun.As the solar activity has obvious periodicity,the performance of ozone in the earth's atmosphere changes,there is more obvious volatility.

Therefore,in order to obtain two important characteristics of trend and cyclical change of atmospheric ozone content,the time series data composed of atmospheric ozone content with time are analyzed by using DHR model to predict the future ozone content.