Atmospheric CO2 mole fraction data observed at Yoyogi, Tokyo by NIES

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This data set contains carbon dioxide (CO2) mole fractions observed on a roof-top tower of Tokai University (37 m above ground) in Yoyogi (YYG; 35.66° N, 139.68° E), Tokyo, Japan. The YYG site is a residential area located near the central part of Tokyo. The main landcover around the site is characterized by residential buildings with a mean height of 9 m.


Release date
Temporal coverage
2017/04/01 - 2020/05/31
Data provider
Email: cgerdb_admin(at)
File format
Data volume
7.67 MB
Ver.1.0 (Last updated: 2021/05/10)

Data Set

Atmospheric mole fractions of CO2
Observation period
From 2017/02/14 (ongoing)
35.66°N, 139.68°E
Elevation: 39 m
Sampling height: 37 m above ground
Measurement method
Air samples were taken at the tower height of 37 m above ground and introduced into a Nafion dryer (MD-050-72S; Perma Pure, NJ, USA) to reduce water vapor. The atmospheric CO2 concentrations have been measured continuously using a wavelength-scanned cavity ring-down spectrometer (WS-CRDS) (G2401; Picarro, CA, USA). The analytical reproducibility (standard deviation of 1-minute averaged values for standard gas measurements) of the CO2 mole fractions was ~0.02 ppm.
Calculation method
The 1-minute values were calculated by averaging the raw data from WS-CRDS (typically every 2-3 seconds) in that minute. The hourly values are then calculated by averaging all the 1-minute values in that hour.
The CO2 mole fractions were determined against the NIES 09 CO2 scales. Three standard gases with different CO2 concentrations were used to calibrate the WS-CRDS every 50 hours.
Date and time are shown based on Japan standard time (UTC+9:00).
In Situ Land-based Platforms > Ground Stations
Atmosphere > Atmospheric Chemistry > Carbon and Hydrocarbon Compounds > Atmospheric Carbon Dioxide > Carbon Dioxide Surface
Update history
Data of 1-minute average values for April and May, 2017-2020 are released. Ver.1.0


Hirofumi Sugawara*1 (ORCID iD
Shigeyuki Ishidoya*2 (ORCID iD
Motoki Sasakawa*3 (ORCID iD
Toshinobu Machida*3 (ORCID iD
*1 National Defense Academy of Japan
*2 National Institute of Advanced Industrial Science and Technology (AIST)
*3 Earth System Division, NIES

Reference Information

Sugawara, H., S. Ishidoya, Y. Terao, Y. Takane, Y. Kikegawa, and K. Nakajima (2021), Anthropogenic CO2 Emissions Changes in An Urban Area of Tokyo, Japan, Due to the COVID-19 Pandemic: A Case Study during the State of Emergency in April–May 2020, in review.

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Terao et al. (2021), Atmospheric CO2 mole fraction data observed at Yoyogi, Tokyo by NIES, Ver. x.x*1, NIES, DOI:10.17595/20210510.001. (Reference date: YYYY/MM/DD)*2
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