Table 2.

Input combinations based on ranking of variable importance.

Variable set	t	SD	PM2.5	Month	CO	PM10	WS	SO2	NO2
A	+	+	+	+	+	+	+	+	+
B	+	+	+	+	+	+	+	+
C	+	+	+	+	+	+	+
D	+	+	+	+	+	+
E	+	+	+	+	+
F	+	+	+	+
G	+	+	+
H	+	+
I	+

SD sunshine duration, WS wind speed.