**********************************************************************
*** Atmospheric CO concentrations (ppbv)  derived from flask       ***
*** samples collected at Alert, NWT, Canada                        ***
*** Source: L.P. Steele                                            ***
***              P.B. Krummel                                      ***  
***              R.L. Langenfelds                                  ***
***              Commonwealth Scientific,                          ***
***              and Industrial Research Organisation,             ***
***              Aspendale, Victoria,                              *** 
***              Australia  3195                                   ***                   
***                                                                ***   
*** February 2003                                                  ***
***                                                                ***
**********************************************************************

Year	Jan.	Feb.	Mar.	Apr.	May	Jun.	Jul.	Aug.	Sep.	Oct.	Nov.	Dec.	Ann. Ave.

1992		186.12	195.8	192.98	159.85	117.9	90.13	86.53	100.89	109.73	123.77	156.43	
1993	180.18	180.32	173.9	178.67	164.55	118.01	85.46	88.76	110.48	122.38	121.59	139.56	138.66
1994	160.85	170.95	185.09	186.69	154.9	113.13	90.29	90.41	110.43	127.61	131.63	148.81	139.23
1995	176.25	181.92	173.1	162.34	131.74	97.79	91.99	94.2	93.06	103.05	117.33	128.81	129.30
1996	145.02	167.56	175.32	158.15	134.22	106.46	86.32	90.78	106.91	123.32	131.42	134.85	130.03
1997	150.65	163.36	163.3	158.81	136.74	103.23	79.61	68.53	76.79	100.1	121.72	144.02	122.24
1998	170.33	182.77	176.86	167.44	152.35	122.12	97.41	103.72	142.41	173.84	174.72	171.94	152.99
1999	174.26	176.8	180.48	177.38	148.61	105.92	83.78	81.95	86.92	97.25	113.7	127.33	129.53
2000	142.87	158.67	162.04	156.4	135.08	101.11	80.07	76.43	84.49	97.47	102.86	118.24	117.98
2001	145.12	151.23	153.83	159.32	140.36	103.85	79.34	79.26	90.55	101.7	114.05	129.22	120.65
					
								
Monthly values, expressed in parts per billion by volume (ppbv), are linked to the gravimetrically derived 
scale of NOAA/CMDL using a single high-pressure cylinder standard with a CO mole fraction of 196 ppbv.  
Stability of the CSIRO scale and variations in instrument response are monitored with about 20 high 
pressure cylinder standards, with lifetimes of 4 to 10 or more years, spanning a CO range of 20 to 
400 ppbv.  Monthly values are calculated as the mean of the daily values from a smooth curve fit to 
the data using curve-fitting routines described by Thoning et al. 1989.  Annual values are the arithmetic 
means of the 12 monthly values.