AQI	Air quality
EEMD	Ensemble empirical mode decomposition
IMF	Intrinsic mode function
ANN	Artificial neural networks
MLR	Multiple linear regression
PCR	Principal component regression
SVR	Support vector regression
GRNN	General regression neural network
IOWA	Induced ordered weighted averaging
NARNN	Nonlinear autoregressive neural network
ES	Exponential smoothing
MM	Mirror method
CFM	Combined forecasting model
MMA	Mean mode accuracy
DM test	Diebold–Mariano test
IR	Improvements of the proposed model
SSE	Sum of squared error
MAE	Mean absolute error
MAPE	Mean absolute percentage error
RMSE	Root mean squared error