Period

Automatic

ppbv, X ± σ

Passive

ppbv

Differences

(%)

Period

Automatic

ppbv, X ± σ

Passive

ppbv

Differences

(%)

January

16.7 ± 8.2

17.4

−4

July

12.3 ± 3.0

10.2

21

February

10.8 ± 6.6

14.1

−23

August

12.7 ± 3.5

14.2

−11

March

19.2 ± 4.7

16.7

15

September

12.4 ± 3.4

16.2

−23

April

25.2 ± 2.9

24.6

2

October

14.3 ± 2.9

16.9

−15

May

20.7 ± 4.7

19.5

6

November

23.4 ± 10.2

19.4

20

June

14.9 ± 4.8

14.6

2

December

16.1 ± 9.4

15.2

6