Continuous Observational Data of Atmospheric N2O Mixing Ratios at Cape Ochi-ishi

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The present data set is time series data of atmospheric N2O mixing ratios measured at Cape Ochi-ishi situated at the base of Nemuro Peninsula in eastern Hokkaido, Japan. The monitoring station is located on top of a cliff 50 m above ground at the southern tip of the cape facing the Pacific Ocean. Air is sampled from an intake placed on a tower adjacent to the observation station about 50 m above ground level, and the N2O mixing ratios are measured semi-continuously by using a gas chromatographic system. The winds tend to be predominantly northwesterly in winter and southwesterly in summer, whereas in spring and autumn no predominant wind direction has been observed.


Release date
Temporal coverage
1999/01/01 - 2014/12/31
Data provider
Email: cgerdb_admin(at)
File format
Data volume
303 KiB
Ver.1.0 (Last updated: 2017/01/13)

Data Set

N2O mixing ratios
Time resolution
1 day (24-hour average from 0:00 to 24:00 on UTC)
0.3 ppb
Observation period
From 1999 (ongoing)
43.1603°N, 145.4974°E
Elevation: 42.5 m;
Sampling height: 51.5 m above ground
Measurement method
From an air intake placed on a steel monitoring tower 51.5 m above ground, outside air is drawn in through a stainless tube to a ground-based observation room using a diaphragm pump. A part of the sampled air is led into a Nafion® tube dryer and a cold trap at -40 °C to reduce water vapor in the sample air. Then the N2O mixing ratio of the dried air sample is determined by a gas chromatograph equipped with a flame ionization detector (GC/ECD).
Every 1 hour, 3 standard gases, which are N2O-in-air mixtures stored in high-pressure cylinders, are measured and calibration curves for the calculation of N2O mixing ratios are determined. The N2O mixing ratios of the standard gases is determined against the NIES96 standard scale developed by the National Institute for Environmental Studies (NIES). Please refer to the webpage "GHGs Monitoring at Hateruma Island and Cape Ochi-ishi" for pictures of the measuring equipment.
Calculation method
The basic GC cycle consists of 6 injections of 3 working standard gases with different N2O mixing ratios followed by 3 air samples at 10-min intervals for each GC analysis. The atmospheric N2O mixing ratios are determined by repeating this basic GC cycle. Every calibration curve for 3 consecutive air samples is determined by the 2 sets of the working standard gas analyses before and after the air sample analyses. The 1-hour value of N2O mixing ratio is the mean mixing ratio of 3 air sample, and the daily averages are calculated from the 1-hour values.
In Situ Land-based Platforms > GROUND STATIONS
Atmosphere > Atmospheric Chemistry > Nitrogen Compounds > Nitrous Oxide
[Free keywords]
Greenhouse gases, Nitrous Oxide, N2O, global warming, Ochi-ishi, continuous observations
Update history
The data from 1999 to 2014 have been compiled in NASA Ames Format 1001. Ver.1.0.


Tohjima et al. (2000) Variations in atmospheric nitrous oxide observed at Hateruma monitoring station, Chemosphere, 2, 435-443. .

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Tohjima et al. (2017), Continuous observational data of atmospheric N2O mixing ratios at Cape Ochi-ishi, Ver. x.x (*1), Center for Global Environmental Research, National Institute for Environmental Studies, DOI:10.17595/20170113.002. (Reference date: YYYY/MM/DD)(*2)
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