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 2006A 1 13 260-370 ppb
SF6 2000 2006 2 13 0-10 ppt
CFC-12 2001 2008 3 15 150-650 ppt
CFC-11 1993 1992 8 20-320 ppt
CFC-113 2003 no change 10 20-110 ppt
CH3CCl3 2003 no change 10 10-180 ppt
CCl4 1996 2008 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
HCFC-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 2003 1 6-35 ppt
C2Cl4 2003 no change 8 5-14 ppt
COS 2002 2004 8 7 260-625 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 0.033 ppt higher than the 2000 scale at 4 ppt. See scale page for more information
3 The 2008 CFC12 scale is 1.3% higher than the 2001 scale, see scale page for more information. Update using Y = 1.002*X + 5.807 ppt
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.: Conversion 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., vol 112, D09035, doi:10.1029/2006JD007954.