Data Set Title: Atmospheric CO2 Concentrations - The Canadian Background Air Pollution Monitoring Network Principal Investigators: Neil B. A. Trivett Vicky C. Hudec Environment Canada Atmospheric Environment Service 4905 Dufferin Street Downsview, Ontario, Canada M3H 5T4 C. S. Wong Marine Carbon Research Centre Institute of Ocean Sciences Sidney, British Columbia, Canada DOI: 10.3334/CDIAC/atg.ndp034 Source and Scope of the Data: Atmospheric CO2 concentrations are provided for three Canadian sites including Alert, Northwest Territories (82 28'N, 62 30'W); Sable Island, Nova Scotia (43 56'N, 60 01'W); and Cape St. James, British Columbia (51 56'N, 131 01'W). The period of record varies by station. The beginning periods of record are July 1975 for Alert, March 1975 for Sable Island, and May 1979 for Cape St. James, respectively. All records extend into July or August of 1992. These concentrations are derived from air samples collected in 2 liter flasks. Approximately, once every week a pair of evacuated 2-L flasks are exposed around noon local time by Atmospheric Environment Service personnel to obtain samples of the ambient air. From each flask, two aliquots are analyzed. The samples are analyzed for CO2 concentration using a Siemans ULTRAMAT III non-dispersive infrared gas analyzer and CO2-in-air calibration gases. The measured concentrations are directly traceable to the WMO primary CO2 standards and each flask sample has been given classified for quality and possible contamination as described below. Data Format: Six ASCII files are provided in this subdirectory including this documentation file (NDP034.TXT); three data files containing atmospheric CO2 concentrations from Alert (ALERT.CO2), Sable Island (SABLE.CO2), and Cape St. James (JAMES.CO2); and a FORTRAN 77 (NDP034.FOR) and SAS (NDP034.SAS) retrieval code that will read and print any of the data files. There are no missing values in the data files and all atmospheric CO2 concentrations are expressed in parts per million by volume (ppm) and reported in the WMO 1983 scale. Each of the data files is formatted as: READ(5,10,END=99) YEAR,MONTH,DAY,JULIAN,DECYR,CO2,FLAG 10 FORMAT(I2,1X,I2,1X,I2,1X,I3,1X,F16.13,1X,F8.4,1X,A1) where: YEAR is the number of years since 1990 (e.g., 92), MONTH is the month expressed as a two-digit integer (i.e., January=1 ....... December=12), DAY is the day of the month, JULIAN is the Julian day, DECYR is the year expressed as a decimal (e.g. 87.23345). CO2 is the atmospheric CO2 concentration expressed in ppm relative to the WMO 1983 scale. FLAG is a single letter code that represents the secondary classification of the flask sample. The codes, their meaning, and the criteria they satisfy are as follows: A = Best Data - 2 flasks, 2 aliquots each - both flasks have an A classification - between flask averages is less than the limit set (i.e., less than 0.6 ppm) B = 2 flasks - one aliquot missing but other is less than CO2 limit - between flask averages is less than the limit set S = Probable sampling error - one flask may be broken (missing) - within flask difference is less than 0.3 ppm - between flask difference is greater than 0.6 ppm L = Probable laboratory analysis error - one aliquot missing and other is analyzed greater than CO2 limit or average of flask is greater than CO2 limit REFERENCES Higuchi, K. and S.M. Daggupaty. 1985. On variability of atmospheric CO2 at station Alert. Atmospheric Environment 19:2039-44. Trivett, N.B.A., and K. Higuchi. 1989. Trends and seasonal cycles of atmospheric CO2 over Alert, Sable Island, and Cape St. James, as analyzed by forward stepwise regression technique. pp. 27-42. IN The Statistical Treatment of CO2 Data Records, W.P. Elliott (ed.). Air Resources Laboratory, Silver Spring, Maryland. Trivett, N.B.A., D.E.J. Worthy, and K.A. Brice. 1989. Surface measurements of carbon dioxide and methane at Alert during an Artic haze event in April, 1986. Journal of Atmospheric Chemistry 9:383-97. Wong, C.S., Y.H. Chan, J.S. Page, R.D. Bellegay, and K.G. Pettit. 1984. Trends of atmospheric CO2 over Canadian WMO background stations at Ocean Weather Station P, Sable Island, and Alert. Journal of Geophysical Research 89:9527-39.