基于时间序列模型与残差控制图的兰州市空气质量研究

Prediction of Air Quality in Lanzhou Using Time Series Model and Residual Control Chart

利用2003-2012年兰州市月均空气污染指数API和季节性时间序列模型SARIMA,对数据序列进行拟合并对其变化趋势进行了分析,研究其演变趋势并选取空气质量良好(月平均API<150)的月份(2012年6月2013年2月),选用时间序列模型ARIMA(1,1,1)进行拟合,再结合残差控制图,对2013年3月日平均API预测监控。结果表明,SARIM A(0,1,1)×(0,1,1)12模型较好的拟合了近10年兰州市API的变化趋势,兰州市的空气污染大致呈冬、春季污染相对较重,夏、秋季相对较轻,空气质量总体在逐渐好转。适合该地区短时间尺度的时间序列模型是ARIMA(1,1,1),结合残差控制图对2013年3月API进行预测监控,结果显示6,9,10,11,12和13日超出控制限,对6日和9日提出预警。预测结果与实际结果相吻合,证实了将时间序列模型与残差控制图结合预测监控大气污染的有效性。

The mean monthly air pollution index( API) in Lanzhou from 2003 to 2012 w as fitted by time series model SARIM A,and seasonal variation and trend of the API w as analyzed. Using combined SARIM A model and residual control chart method,a model has been established to forecast daily API in Lanzhou. This model firstly need to select an appropriate stage as a control state from the fitted API data series from 2003 to 2012 using the time series model ARIM A. In the present study,w e selected the months from June 2012 to February 2013 as the control state to establish control limits based on the ARIM A( 1,1,1) fitting for 2003 2012 API data. The model then employed a residual control chart method to forecast and monitor the average daily API in Lanzhou in M arch 2013. Results indicate that SARIM A( 0,1,1) ×( 0,1,1)12model yielded a better-fit to API in Lanzhou City,show ing higher air pollution in w inter and spring and relatively mild pollution during summer and autumn. Overall both modeled and monitored data revealed the improvement of air quality in Lanzhou for the last decade. Residual control charts model for M arch 2013 API established in this study predicted that API on 6,9,10,11,12,13 exceeded the control limits,and issued a w arning on API in 6 and 9 M arch,respectively. The model forecasting results are consistent with the monitored results,confirming the usefulness and reliability of the model using combined time series model and residual control chart.