This section describes the content and format of each of the 163 files that
compose this NDP and the NOAA/CMDL flask CO2 database.
Data Files
This NDP consists of the following 163 files:
The file names are the appropriate 3-letter codes with the extension .co2
(e.g., alt.co2 identifies the file for Alert, Northwest Territories, Canada). For
the shipboard programs, the data have been grouped into 5-degree (PAC, PAW) or 3-degree (SCS) latitude bins.
The file names consist of the appropriate 3-letter code plus an additional 3 characters identifying the
latitude bin and the .co2 extension. The first additional character specifies the
hemisphere (n = northern, s = southern) and the two digits specify the
latitude on which the 5-degree (PAC, PAW) or 3-degree (SCS) latitude bins are centered. The equator
is specified by 000.
Data Format for Files Containing CO2 Mixing Ratios from Individual Flask Samples
This numeric data package contains 101 data files containing CO2 mixing ratios in air samples collected in glass flasks at NOAA/CMDL flask network sites. The mixing ratios were determined by a nondispersive infrared absorption technique. One data file (all.co2) contains measurements from all 42 past and present NOAA/CMDL fixed-position sampling sites. Individual files are also provided for each sampling site (*.co2) and for each latitude band covered by shipboard measurements (e.g., pacn05.co2). The individual files are named according to the station codes used by NOAA/CMDL (see description of the variable STA below). For the shipboard programs the data have been grouped into 5-degree (PAC, PAW) or 3-degree (SCS) latitude bins. The file names consist of the appropriate 3-letter code plus an additional 3 characters identifying the latitude bin and the .co2 extension. The first additional character specifies the hemisphere (n = northern, s = southern) and the two digits specify the latitude on which the 5-degree (PAC, PAW) or 3-degree (SCS) latitude bins are centered. The equator is specified by 000.
All data files have the same format. Each file is sorted by sample collection date and may be read with the following FORTRAN 77 code:
CHARACTER STA*3,FLASKID*8,SMETHOD*1,DATASEL*3,INSTRU*2,DAYFILE*6
READ(5,100,END=99) STA,YYYY,MM,DD,HR,MIN,FLASKID,SMETHOD,CO2,
1 DATASEL,INSTRU,SAMYY,SAMMM,SAMDD,DAYFILE
100 FORMAT(A3,1X,I4,1X,I2,1X,I2,1X,I2,1X,I2,1X,A8,1X,A1,2X,
1 F7.2,1X,A3,1X,A2,1X,I4,1X,I2,1X,I2,1X,A6)
The following SAS® input statement may also be used to read these files:
input sta $ 1-3 yyyy 5-8 mm 10-11 dd 13-14 hr 16-17 min 19-20 flaskid $ 22-29
smethod $ 31 co2 34-40 datasel $ 42-44 instru $ 46-47 samyy 49-52
sammm 54-55 samdd 57-58 dayfile $ 60-65;
________________________________________________________________________________
Variable Variable Starting Ending
Variable type width column column
________________________________________________________________________________
STA Character 3 1 3
YYYY Numeric 4 5 8
MM Numeric 2 10 11
DD Numeric 2 13 14
HR Numeric 2 16 17
MIN Numeric 2 19 20
FLASKID Alphanumeric 8 22 29
SMETHOD Character 1 31 31
CO2 Numeric 7 34 40
DATASEL Character 3 42 44
INSTRU Alphanumeric 2 46 47
SAMYY Numeric 4 49 52
SAMMM Numeric 2 54 55
SAMDD Numeric 2 57 58
DAYFILE Alphanumeric 6 60 65
________________________________________________________________________________
where
STA is the three-letter station or ocean cruise code. The codes and the stations or ocean
cruises they denote are as follows:
ALT Alert, Northwest Territories, Canada
AMS Amsterdam Island, Indian Ocean (France)
ASC Ascension Island, Atlantic Ocean (United Kingdom)
AVI St. Croix, Virgin Islands, United States
AZR Azores (Terceira Island), North Atlantic Ocean (Portugal)
BAL Baltic Sea (Poland)
BME Bermuda (east), North Atlantic Ocean (United Kingdom)
BMW Bermuda (west), North Atlantic Ocean (United Kingdom)
BRW Point Barrow, Alaska, United States
CBA Cold Bay, Alaska, United States
CGO Cape Grim, Tasmania, Australia
CHR Christmas Island, (Kiribati)
CMO Cape Meares, Oregon, United States
CRZ Crozet, Indian Ocean (France)
GMI Guam, Pacific Ocean (United States)
GOZ Dwejra Point, Gozo, Malta
HBA Halley Bay, Antarctica
HUN Hegyhatsal, Hungary
ICE Heimaey, Vestmannaeyjar, Iceland
ITN Grifton, North Carolina, United States
IZO Iza¤a Observatory, Tenerife, Canary Islands, Spain
KEY Key Biscayne, Florida, United States
KUM Cape Kumukahi, Hawaii, United States
MBC Mould Bay, Northwest Territories, Canada
MHT Mace Head, County Galway, Ireland
MID Sand Island (Midway Islands), Pacific Ocean (United States)
MLO Mauna Loa Observatory, Hawaii, United States
NWR Niwot Ridge, Colorado, United States
OPC shipboard measurements in the Pacific Ocean aboard the California Star
PAC shipboard measurements in the Pacific Ocean aboard the Southland Star
PAW shipboard measurements in the Pacific Ocean aboard the Wellington Star
PSA Palmer Station (Anvers Island), Antarctica
QPC Qinghai Province, Peoples Republic of China
RPB Ragged Point, Barbados
SCS shipboard measurements in the South China Sea aboard the Carla A. Hills
SEY Seychelles (Mahe Island), Indian Ocean
SGI South Georgia Island, South Atlantic Ocean (United Kingdom)
SHM Shemya Island, Alaska, United States
SMO American Samoa (United States)
SPO South Pole (Amundsen Scott), Antarctica
STC Ocean Station "C," North Atlantic Ocean (United States)
STM Ocean Station "M," Norwegian Sea (Norway)
SYO Syowa Station, Antarctica
TAP Tae-ahn Peninsula, South Korea
UTA Wendover, Utah, United States
UUM Ulaan Uul, Mongolia
YYYY is the four-digit Greenwich Mean Time (GMT) year when the air sample was collected.
MM is the two-digit GMT month when the air sample was collected. Missing values are
denoted by 99.
DD is the two-digit GMT day when the air sample was collected. Missing values are
denoted by 99.
HR is the two-digit GMT hour when the air sample was collected. Missing values are
denoted by 99.
MIN is the two-digit GMT minute when the air sample was collected. Missing values are
denoted by 99.
FLASKID is the flask sample identification number. These identification numbers may be
numeric, character, or alphanumeric with one to eight characters.
SMETHOD is a one-letter code that identifies the sample collection method. The codes and their
meaning are as follows:
P is a sample collected by means of a portable, battery-powered pumping unit.
Two flasks are connected in series, flushed with air, and then pressurized
to 1.2-1.5 times ambient pressure.
T is an evacuated flask filled by opening an O-ring sealed stopcock.
S are flasks filled at NOAA/CMDL observatories by sampling air
from the in situ CO2 measurement air-intake system.
N are flasks filled, before 1981, by means of a hand-held aspirator bulb and,
since 1981, by means of a pump different from those used in method P.
F are 5-L evacuated flasks filled by opening a greased, ground-glass stopcock.
CO2 is the atmospheric CO2 mixing ratio expressed in parts per million (ppm) relative to
the SIO X93 manometric scale. Missing values are denoted by -999.99.
DATASEL is a three-character code that reflects the results of the NOAA/CMDL data selection
process. Because samples are collected in pairs, the pair difference is calculated, and
samples with a pair difference >0.5 ppm are flagged. Through 1988,
one or both members of a bad pair were sometimes retained if they fell within ±3
sigma from a fitted curve. However, from 1989 to the present, both members of bad
pairs have been automatically rejected. Retained and rejected flasks are flagged as
follows. (NOTE: if either the first or second of these three characters is not a period,
the sample has been rejected.)
Flag Description
Retained ... (3 periods) good pair (D less than or equal to 0.5 ppm)
..H high member of bad pair; retained
..L low member of bad pair; retained
..S single flask; retained
rejected .X. rejected as not representative of
background conditions (>3 sigma from a
fitted curve)
+.. high member of bad pair; rejected
-.. low member of bad pair; rejected
R.. single flask; rejected
*.. off scale or broken flask; rejected
N.. rejected due to error in sampling
or analysis
T.. sample collected as part of a methods test;
not used in data analysis
***************************************** WARNING ******************************************To avoid erroneous analysis and interpretation of these data, users should read and understand these codes before using the data files. It is also strongly recommended that users consult the relevant published literature. NOAA/CMDL has attempted to provide the most accurate and precise measurements possible in a timely manner. However, NOAA/CMDL reserves the right to adjust the data in these files on the basis of recalibrations of reference gases and instruments.
Users of these data should be aware that data selection is a difficult but necessary aspect of the analysis
and interpretation of atmospheric trace gas data sets, and the specific data selection scheme used may be
determined by the goals of a particular investigation. It is possible, and even likely, that some of the
rejected values are valid measurements but represent poorly mixed air masses influenced by local anthropogenic
sources or strong local biospheric sources or sinks. The retained values compose the data set that Tom Conway,
Pieter Tans, and the NOAA/CMDL Carbon Cycle Group staff feel best represents the CO2 distribution
in the remote, well-mixed global troposphere. These are the values they use in their studies of the global
carbon cycle to calculate long-term trends and interannual and seasonal variations.
*********************************************************************************************
INSTRU is a two-character code that identifies the instrument used for the
CO2 determination. The codes and the instruments they denote are as follows:
L1 Lira 200 #1809
L2 Lira 202 #20719
S1 Siemens Ultramat3 #U08-450
U1 UNOR 2 #631710
U2 UNOR 2 #631521
U3 UNOR 4N #719
SAMYY is the year in local time of the CO2 measurement.
SAMMM is the month in local time of the CO2 measurement.
SAMDD is the day in local time of the CO2 measurement.
DAYFILE is a six-character number that identifies the daily file for this analysis date.This numeric data package provides 57 data files containing monthly CO2 mixing ratios derived from individual flask measurements. One data file (allmm.co2) contains monthly CO2 mixing ratios from all the past and present fixed-position NOAA/CMDL sampling sites. Separate files are also provided for each sampling site (*mm.co2) and for each latitude band covered by shipboard measurements in the Pacific Ocean taken aboard the Wellington Star and Southland Star (e.g., pocn05mm.co2). Because the sampling frequency for each 5-degree latitude band covered by the Wellington Star and Southland Star cruise lines is insufficient to calculate monthly means, the measurements from these two cruise lines were merged to calculate monthly means for fourteen 5-degree latitude bands from 30° N to 35° S. No monthly mean file for South Georgia Island exists because there is not sufficient data to calculate monthly means for this site. The individual files are named according to the station codes used by NOAA/CMDL (see description of the variable STA on pages 32-33). The data for the shipboard measurements have been grouped into 5-degree latitude intervals. The file names consist of the appropriate 3-letter code plus an additional 5 characters identifying the latitude band, monthly data (i.e., mm), and the .co2 extension. The first additional character specifies the hemisphere (n = northern, s = southern). The next two digits specify the 5-degree latitude band. The equator is specified by 000. All data files have the same format with one line for each monthly value. Each file is sorted chronologically and may be read with the following FORTRAN 77 code:
C
C SKIP HEADER RECORD THAT IDENTIFIES CONWAY AND TANS AS
C THE DATA SOURCE - PLEASE CREDIT CONWAY & TANS WHEN USING
C THESE DATA!
C
READ(5,75)
75 FORMAT(/,/,/,/,/,/,/,/,/)
C
C READ AND WRITE DATA
C
1 CONTINUE
READ(5,100,END=99) STA,YYYY,MM,CO2
100 FORMAT(A3,1X,I4,1X,I2,2X,F7.2)
These files may also be read with the following SAS® input statement:
________________________________________________________________________________
Variable Variable Starting Ending
Variable type width column column
________________________________________________________________________________
STA Character A3 1 3
YYYY Numeric I4 5 8
MM Numeric I2 10 11
CO2 Numeric F7.2 14 20
_________________________________________________________________________________
where
STA is the three-letter station or ocean cruise code. The codes and the stations or ocean
cruises they denote are shown on pages 32-33.
YYYY is the year.
MM is the month expressed as an integer value (i.e., January = 1, February = 2, ....
December = 12).
CO2 is the monthly CO2 mixing ratio expressed in parts per million (ppm) according to the
SIO X93 manometric scale. The monthly means were calculated from a smooth curve
obtained by a combination of curve fitting and digital filtering based on the methods of
Thoning et al. (1989) and Tans et al. (1989b). The value -999.99 denotes months
where there was not sufficient data to calculate a monthly mean.
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