O2/N2 ratios and CO2 mole fractions of air samples collected at Hateruma Island

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The present data set is time series data of atmospheric O2/N2 ratios and CO2 mole fractions from air samples collected on Hateruma Island, Japan. Hateruma Island is a small ellipse-shaped island in east-west direction with an area of 13 km2 and is the southwestern-most inhabited island of the Japanese archipelago with a population of 500. The monitoring station is located at the eastern tip of the island. Air samples, drawn by a pump from an intake placed on a tower at a height of 37 m above ground level, are forced into Pyrex glass flasks. The collected air samples are sent back to a laboratory in NIES, where O2/N2 ratios and CO2 mole fractions are measured.


Release date
Temporal coverage
1997/07/16 - 2022/03/23
Data provider
Email: cgerdb_admin(at)nies.go.jp
File format
Data volume
150 KB
Latest version
Ver 1.0 (Last updated: 2023/08/30)

Data Set

O2/N2 ratio, CO2 mole fraction
5 per meg
Observation period
From Jul. 16, 1997 (ongoing)
24.06069°N, 123.80939°E
Elevation: 10 m;
Sampling height: 37 m above ground;
Altitude: 47 m
Measurement method
From an air intake placed on a steel monitoring tower 37 m above ground (47 m above sea level), outside air is drawn in through a stainless tube to a ground-based observation room using a diaphragm pump. After passing through a cold trap(−40℃) to reduce water vapor, the air samples are forced into Pyrex glass flasks equipped with two glass stopcocks sealed by Viton O-rings to a pressure of 0.2 MPa (0.1 MPa above the ambient pressure). The collected air samples are sent back to a laboratory in NIES, where O2/N2 ratios and CO2 mole fractions are measured by a gas chromatograph equipped with a thermal conductivity detector (GC/TCD) and a non-dispersive infrared analyzer (NDIR), respectively.
Calculation method
The O2/N2 ratios of the air samples are reported as relative deviations from a reference gas according to δ(O2/N2)={(O2/N2)sample/(O2/N2)reference-1}x106, which are express in per meg units. The reported δ(O2/N2) values and CO2 mole fractions are determined against the NIES original O2/N2 scale and NIES 09 CO2 scale.
[Free keywords]
Atmospheric oxygen
Ground station
Global carbon cycle
Update history
The data from 1999 to 2022 have been compiled in NASA Ames Format 1001. Ver.1.0.
Discrete flask sample

References Information

Tohjima, Y. (2000), Method for measuring changes in the atmospheric O2/N2 ratio by a gas chromatograph equipped with a thermal conductivity detector, J. Geophys. Res., 105, doi:10.1029/2000JD900057.
Tohjima, Y., H. Mukai, T. Machida, and Y. Nojiri (2003), Gas-chromatographic measurements of the atmospheric oxygen/nitrogen ratio at Hateruma Island and Cape Ochi-ishi, Japan, Geophys. Res. Lett., 30(12), 1653, doi:10.1029/2003GL017282.
Tohjima, Y., H. Mukai, Y. Nojiri, H. Yamagishi, and T. Machida (2008), Atmospheric O2/N2 measurements at two Japanese sites: Estimation of global oceanic and land biotic carbon sinks and analysis of the variations in atmospheric potential oxygen (APO), Tellus, 60B, 213–225, doi:10.1111/j.1600-0889.2007.00334.x.
Tohjima, Y., H. Mukai, T. Machida, Y. Hoshina, and S. Nakaoka, Global carbon budgets estimated from atmospheric O2/N2 and CO2 observations in the western Pacific region over a 15-year period, Atmos. Chem. Phys., 19, 9269-9285, 2019, doi:10.5194/acp-19-9269-2019.
Grant Agency
Ministry of the Environment
Grant Number

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Citation format
When this data set is referred to in publications, it should, as a general rule, be made in the following format.
Tohjima et al. (2023), O2/N2 ratios and CO2 mole fractions of air samples collected at Hateruma lsland, Ver.x.x *1, NIES, DOI:10.17595/20230830.002. (Reference date*2: YYYY/MM/DD)
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*2 As the reference date, please indicate the date you downloaded the files.

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