ANN	Artificial neural network
CMAQ	Community multiscale air quality
CO	Carbon monoxide
CPC	Condensation particle counter
FFNN	Feed-forward neural network
LASSO	Least absolute shrinkage and selection operator
LSTM	Long short-term memory
MAE	Mean absolute error
MENA	Middle East and North Africa
NNs	Neural networks
NO${}_2$	Nitrogen dioxide
O${}_3$	Ozone
OPS	Optical particle sizer
P	Absolute pressure
PCC	Pearson correlation coefficients
PM	Particulate matter
PM${}_{10}$	Particulate matter smaller than 10 $\mathsf{\mu }$m
PM${}_{2.5}$	Particulate matter smaller than 2.5 $\mathsf{\mu }$m
PN	Particle number
R${}^2$	Coefficient of determination
ReLU	Rectified linear unit
RF	Precipitation
RH	Relative humidity
RMSE	Root mean squared error
RNN	Recurrent neural network
SMPS	Scanning Mobility Particle Sizer
SO${}_2$	Sulfur dioxide
T	Temperature
TDNN	Time-delay neural network
UAM	Urban airshed model
UFPs	Ultra-fine particles
WD	Wind direction
WHO	World Health Organization
WS	Wind speed