Abstract. Despite recent progress of numerical air quality models,
accurate prediction of fine particulate matter (PM2.5) is still
challenging because of uncertainties in physical and chemical
parameterizations, meteorological data, and emission inventory databases.
Recent advances in artificial neural networks can be used to overcome
limitations in numerical air quality models. In this study, a deep neural
network (DNN) model was developed for a 3 d forecasting of 6 h average
PM2.5 concentrations: the day of prediction (D+0), 1 d after
prediction (D+1), and 2 d after prediction (D+2). The DNN model was
evaluated against the currently operational Community Multiscale Air Quality
(CMAQ) modeling system in South Korea. Our study demonstrated that the DNN
model outperformed the CMAQ modeling results. The DNN model provided better
forecasting skills by reducing the root-mean-squared error (RMSE) by 4.1, 2.2, and 3.0 µg m−3 for the 3
consecutive days, respectively, compared with the CMAQ. Also, the false-alarm
rate (FAR) decreased by 16.9 %p (D+0), 7.5 %p (D+1), and 7.6 %p (D+2), indicating that the DNN model substantially mitigated the
overprediction of the CMAQ in high PM2.5 concentrations. These results
showed that the DNN model outperformed the CMAQ model when it was
simultaneously trained by using the observation and forecasting data from
the numerical air quality models. Notably, the forecasting data provided
more benefits to the DNN modeling results as the forecasting days
increased. Our results suggest that our data-driven machine learning
approach can be a useful tool for air quality forecasting when it is
implemented with air quality models together by reducing model-oriented
systematic biases.