Abstract:

Using the rainfall data provided by the Nanchang Weather Bureau and Statistical Yearbook Data by Nanchang city, Jiangxi Province, this paper analyzed the changes in rainfall time series and suburban rainfall characteristics in Nanchang city. In order to analyze rainfall data from 1951 to 2007, various methods have been used, including trend analysis, moving average and correlation analysis. It studied the multiple time scale features, periodic variation, different rainfall intensity and rainfall mutation characteristics about the rainfall in Nanchang city. There is another process which is made a prediction for the change of annual rainfall and the rainfall of the four seasons in the same time. The urbanization process is studied on the influence of rainfall characteristics through the outskirts of contrast analysis method. This paper also discussed the existence of “rain island effect” in Nanchang city. The results showed that, precipitation in flood season did not increase along with the urbanization. However, the seasonality of rainfall become more obvious. In spring and summer, the rainfall presents the downward trend in general. In contrary, rainfall in autumn and winter, tends to increase. Furthermore, the changes in seasonality of rainfall were found to be affected at both large and small scales. The results also showed that the overall trend in the seasonality of rainfall in the next few years will be consistent with the annual rainfall. The overall rainfall trends to slightly reduce, suggesting that there is no obvious “rain island effect” in Nanchang city. At the same time, urbanization was found to contribute 2.8% to the increased rainfall, indicating slight effect urbanization of rainfall. Further analysis suggested that rainfall has the tendency of centralization. The uneven rainfall distribution has become more obvious. Because of the influence of urbanization, rainfall frequency will increase Nanchang city’s urban. At the same time, the urban heavy rainfall frequency will increase as well and the probability will also become higher. 〖JP2〗Among them the biggest influence of torrential rain occurred frequency and probability, which will directly affect the urban drainage engineering standards existing and proposed but also will affect the safety of rain flood drainage design.