Continuous Observational Data of Atmospheric CO2 Mixing Ratios at Cape Ochi-ishi

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The present data set is a set of continuous observational data of background CO2 mixing ratios in the vicinity of 40°N in the northern region of East Asia, measured at Cape Ochi-ishi situated on Nemuro Peninsula, Hokkaido, Japan. Because Cape Ochi-ishi, stretching into the Pacific Ocean, has a low population density and because the cape itself is a protected area with limited access, it is subjected to very small influence from local anthropogenic CO2 emissions. In summer, Cape Ochi-ishi is under the influence of air masses transported from the direction of the Pacific Ocean and Japan, and in winter it is influenced by the air masses transported from the direction of Siberia and the North Pole.


Release date
Temporal coverage
1995/01/01 - 2022/12/31
Data provider
Email: cgerdb_admin(at)
File format
Data volume
Ver.1.2 (Last updated: 2023/06/30)

Data Set

CO2 mixing ratios
Time resolution
1 hour (60 minutes preceding the hour)
0.01 ppm
Observation period
From 1995 (ongoing)
43.16028°N, 145.49739°E
Elevation: 42.4 m;
Sampling height: 51.5 m above ground;
Altitude: 93.9 m
Measurement method
Air is sampled at a height of 51.5 m above ground by a sampling inlet mounted on a steel monitoring tower through a stainless tube to a ground-based observation room using a diaphragm pump. The sampled air is led into a measuring line where it goes through primary dehumidification at -45 °C and secondary dehumidification at -70 °C, after which the mixing ratios are determined using a measuring equipment (NDIR).
Every 3 hours, 4 cylinders of standard gases are measured and the CO2 mixing ratios are calibrated. Calibration of the standard gases is carried out using the NIES09 standard gas series developed by NIES.
Please refer to the webpage "GHGs Monitoring at Hateruma Island and Cape Ochi-ishi" for pictures of the measuring equipment.
Calculation method
First, CO2 mixing ratio values measured at 1-second intervals are averaged over 5 seconds, and then 12 such 5-second averages are averaged to produce an average mixing ratio value over a 1-minute period. The hourly values are then calculated by averaging all the 1-minute values in that hour.
The calibrated CO2 mixing ratio values are the time-weighted average values calculated from the calibration curve right before and after the measurements.
In Situ Land-based Platforms > GROUND STATIONS
Atmosphere > Atmospheric Chemistry > Carbon and Hydrocarbon Compounds > Carbon Dioxide
[Free keywords]
Greenhouse gases, carbon dioxide, CO2, global warming, Ochi-ishi, continuous observations, infrared analyzer
Update history
A new data set for the period between January 2014 and December 2022 has been added. Ver.1.2.
The data set has been reconstructed due to a revision of the Conditions and Terms of Use, and a new data set for the period between January 2011 and December 2013 has been added. Ver.1.1.
The data from 1995 to 2010 have been compiled in NASA Ames Format 1001. Ver.1.0.


Project manager
Data manager
Shigeru Hashimoto (*1), Keiichi Katsumata (*1), Toshinobu Machida (*1), Noritsugu Tsuda(*2)
(*2) Global Environmental Forum


Mukai, H., Katsumoto, M., Ide, R., Machida, T., Fujinuma, Y., Nojiri,Y., Inagaki, M., Oda, N., Watai, T. (2001), Characterization of atmospheric CO2 observed at two-background air monitoring stations (Hateruma and Ochi-ishi) in Japan, Sixth International Carbon Dioxide Conference Extend Abstract, 1, 108-111, Organizing Committee of Sixth International Carbon Dioxide Conference, Sendai, Japan.

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Mukai et al. (2014), Continuous observational data of atmospheric CO2 mixing ratios at Cape Ochi-ishi, Ver. x.x (*1), Center for Global Environmental Research, National Institute for Environmental Studies, DOI:10.17595/20160901.002. (Reference date: YYYY/MM/DD)(*2)
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