PM<sub>10</sub> Forecasting Using Soft Computing Techniques

Abstract

Air quality forecasting has acquired great significance in environmental sciences due to its adverse affects on humans and the environment. The artificial neural network is one of the most common soft computing techniques that can be applied for modeling such complex problem. This study designed air quality forecasting model using three-layer FFNN's and recurrent Elman network to forecast PM10 air pollutant concentrations 1 day advance in Yilan County, Taiwan. Then, the optimal model is selected based on testing performance measurements (RMSE, MAE, r, IA and VAF) and learning time. This study used an hourly historical data set from 1/1/2009-31/12/2011 collected by Dongshan station. The data was entirely pre-processed and cleared form missing and outlier values then transformed into daily average values. The final results showed that the three-layer FFNN with One Step Secant (OSS) training algorithm achieved better results than Elman network with Gradient Descent adaptive learning rate (GDX) training algorithm. Where, the FFNN required the less training time and achieved better performance in forecasting PM10 concentrations. Also, the testing performance measurements shown that the selected daily average input variables in previous day (PM_2.5), relative humidity, PM10, temperature, wind direction and speed is critical to give better forecasting accuracy. Whereas, the testing measurements RMSE = 6.23 μg/m₃, MAE = 4.75 μg/m₃, r = 0.943, IA = 0.964 and VAF = 88.80 in PM₁₀ FFNN forecasting model that used OSS training algorithm.