Current calibration scales for a number of trace species measured by CMDL are summarized in Table 1

Last Update: April 26, 2007

by: Brad Hall

 

Current calibration scales for a number of trace species measured by GMD are summarized in the Table. The scales shown are tied to a specific set of primary standards [Hall et al., 2001] and named according to the year in which they were adopted.  Thus, the preparation and use of new primary standards for a particular compound results in a new scale for that compound.  Also shown in Table 1 is the number of primary standards used to define each scale and the concentration range of those standards.

 

Species

Previous Scale

Current Scale
Note

N

Range

N2O

2000

2006
1

13

260-370 ppb
SF6
2000
2006
2
13
0-10 ppt

CFC-12

2001

no change

15

150-650 ppt

CFC-11

1993

1992
3

8

20-320 ppt

CFC-113

2003

no change

10

20-110 ppt

CH3CCl3

2003

no change

10

10-180 ppt

CCl4

1996

2006
4

7

25-150 ppt

Halon-1211

1996

2006
5

5

3-7 ppt

Halon-1301

1990

2006
6

6

2-5 ppt

HCFC-22

1992

 2006
7

9

75-200 ppt

HCFC-141b

1994

no change

3

5-50 ppt

HCFC-142b

1994

no change

3

5-50 ppt

HFC-134a

1995

no change

2

5-10 ppt
HFC-152a
None
2004
2
5-11 ppt

CH3Cl

2003

no change

9

280-810 ppt

CH3Br

2003

no change

9

8-390 ppt

CHCl3

2003

no change

1

4-13 ppt

CH2Cl2

1992

no change

1

6-35 ppt

C2Cl4

2003

no change

8

5-14 ppt

COS

2002

2004
8

7

260­625 ppt

CHBr3

2003

no change

2

5-11 ppt
CH2Br2
2003
2004
9
2
10-20 ppt

Benzene

None

2006

2

50-100 ppt

Notes

1 The 2006 N2O scale is 0.19 ppb lower than the 2000 scale at 320 ppb.
2 The 2006 SF6 scale is equivalent to the 2000 scale over the range 3-8 ppt. See scale page for more information
3

The scale change is in name only. The scale should have been identified as 1992.

4 Seven standards prepared from 2001-2004 are now used to define te scale. These seven standards are consistent to withoiin 0.5%. Four standards prepared in 1996 have been removed from the scale. For ECD-based results the conversion in 0.9954 at 95 ppt. For GCMS results the conversion is 0.9853.
5 The 2006 scale is 1% higher than the 1996 scale. The conversion factor is 1.011.
6 The 2006 halon-1301 scale is 13% higher than the 1996 scale. The conversion factor is 1.13.
7 Five standards were added to the four than defined the 1992 scale. The 2006 scale is 0.5% higher than the 1992 scale.: Cocversion factor 1.005.
8 Two Aculife-treated standards were replaced by stainless steel standards in 2004.
9 The scale change is in name only. The original assigment of 2003 was in error.


Montzka, S.A., J.H. Butler, B.D. Hall, D.J. Mondeel, and J.W. Elkins, 2003, A decline in tropospheric organic bromine, Geophys. Res. Lett., 30(15), 1826, doi:10.1029/2003GL017745.

Hall, B.D., G.S. Dutton, and J.W. Elkins, (2007), The NOAA nitrous oxide standards scale for atmospheric observations, J. Geophys. Res., in press.