Variables

Total

Spring

Summer

Autumn

Winter

p value

PM_2.5, mean ± SD (μg/m³)

whole day (24 hours)

26.7 ± 19.2

30.7 ± 19.3

12.7 ± 10.0

29.7 ± 17.5

33.7 ± 20.5

<0.001

Daytime

27.5 ± 19.4

30.6 ± 19.5

13.0 ± 10.0

31.8 ± 17.4

34.6 ± 20.7

<0.001

Nighttime

25.9 ± 18.9

30.8 ± 19.2

12.5 ± 10.0

27.5 ± 17.2

32.8 ± 20.3

<0.001

PM_2.5, hourly records > Q3

whole day (24 hours)

10,580 (24.9%)

3598 (33.7%)

318 (3.0%)

2903 (27.3%)

3761 (35.2%)

<0.001

Daytime

5586 (13.1%)

1739 (16.3%)

166 (1.6%)

1705 (16.0%)

1976 (18.5%)

<0.001

Nighttime

4994 (11.8%)

1859 (17.4%)

152 (1.4%)

1198 (11.3%)

1785 (16.7%)

<0.001

Rainfall (per hour records), n (%)

whole day (24 hours)

2205/42,499 (5.2)

763/10,665 (7.2)

833/10,514 (7.9)

257/10,633 (2.4)

352/10,687 (3.3)

<0.001

Daytime

1145/21,028 (5.4)

384/5272 (7.3)

449/5204 (8.6)

136/5262 (2.6)

176/5290 (3.3)

<0.001

Nighttime

1060/21,471 (4.9)

379/5393 (7.0)

384/5310 (7.2)

121/5371 (2.3)

176/5397 (3.3)

<0.001

Temperature, mean ± SD (degree C)

whole day (24 hours)

23.9 ± 5.0

23.2 ± 4.0

28.7 ± 2.1

25.7 ± 3.1

18.0 ± 3.0

<0.001

Daytime

24.8 ± 5.2

24.1 ± 4.2

29.7 ± 2.2

26.7 ± 3.1

18.8 ± 3.1

<0.001

Nighttime

23.0 ± 4.7

22.3 ± 3.7

27.7 ± 1.5

24.8 ± 2.8

17.4 ± 2.8

<0.001

Relative humidity, mean ± SD (%)

whole day (24 hours)

81.4 ± 10.1

82.0 ± 10.6

82.8 ± 8.7

80.5 ± 10.0

80.2 ± 10.6

<0.001

Daytime

77.2 ± 10.3

77.4 ± 11.3

78.0 ± 9.0

76.6 ± 9.9

77.0 ± 10.9

<0.001

Nighttime

85.4 ± 7.9

86.5 ± 7.5

87.4 ± 5.3

84.4 ± 8.5

83.3 ± 9.2

<0.001

Wind direction, mean (degree)

Whole day

100.2

126.8

203.7

71.4

67.8

<0.001

Daytime

122.5

184.3

220.4

76.4

72.4

<0.001

Nighttime

88.9

94.6

178.6

67.5

63.4

<0.001

Wind speed, mean (m/second)

Whole day

0.58

0.34

1.30

0.92

1.79

<0.001

Daytime

0.42

0.37

1.68

0.83

1.77

<0.001

Nighttime

0.79

0.57

1.11

1.02

1.81

<0.001