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|
|CFC-113||2003||no change||10||20-110 ppt|
|CH3CCl3||2003||no change||10||10-180 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|
|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|
|CHBr3||2003||no change||2||5-11 ppt|
|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.