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The present data set is time series data of atmospheric methane (CH4) 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 42.4 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 about51.5 m above ground level, and the CH4 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. Because Hokkaido’s eastern part is dotted with swamps and grazing lands which are methane sources, and two cities, Nemuro and Kushiro are situated 20 km north and 100 km west, respectively, of the station, the influence from local methane emission sources is frequently observed.
Description
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Supervisor
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Release date
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2016/09/01
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Temporal coverage
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1995/01/01 - 2022/12/31
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Data provider
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NIES
Email: cgerdb_admin(at)nies.go.jp |
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DOI
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File format
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Data volume
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10.7MB
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Version
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Ver.1.1 (Last updated: 2023/06/30)
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Language
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English
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Data Set
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Parameters
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CH4 mixing ratios
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Time resolution
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1 hour (60 minutes preceding the hour)
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Precision
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2 ppb
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Observation period
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From 1995 (ongoing)
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Location
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43.16028°N, 145.49739°E
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Altitude
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Elevation: 42.4 m;
Sampling height: 51.5 m above ground; Altitude: 93.9 m; |
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Measurement method
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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 CH4 mixing ratio of the dried air sample is determined by a gas chromatograph equipped with a flame ionization detector (GC/FID).
Every 2 hours, 3 standard gases, which are CH4-in-air mixtures stored in high-pressure cylinders, are measured and calibration curves for the calculation of CH4 mixing ratios are determined. The CH4 mixing ratios of the standard gases is determined against the NIES94 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. |
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Calculation method
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The basic GC cycle consists of 12 injections of 3 working standard gases with different CH4 mixing ratios followed by 9 air samples at 10-min intervals for each GC analysis. The atmospheric CH4 mixing ratios are determined by repeating this basic GC cycle. Every calibration curve for 9 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 methane mixing ratios is the mean mixing ratio of 3-6 air samples.
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Keywords
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[GCMD_Platform]
In Situ Land-based Platforms > GROUND STATIONS
[GCMD_Science]Atmosphere > Atmospheric Chemistry > Carbon and Hydrocarbon Compounds > Methane
[Free keywords]Greenhouse gases, methane, CH4, global warming, Ochi-ishi, continuous observations
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Update history
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[2023/06/30]
A new data set for the period between January 2016 and December 2022 has been added. Ver.1.1.
[2016/09/01]The data from 1995 to 2015 have been compiled in NASA Ames Format 1001. Ver.1.0.
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Creators
Contributors
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Project manager
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Data manager
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Yasunori Tohjima (*1), Keiichi Katsumata (*2), Toshinobu Machida (*2)
(*1) Center for Environmental Measurement and Analysis (*2) CGER, NIES |
References
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References
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Tohjima et al. (2002), Analysis and presentation of in situ atmospheric methane measurements from Cape Ochi-ishi and Hateruma Island, J. Geophys. Res., 107, 4148, DOI:10.1029/2001JD001003.
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Terms and Conditions of Use*
*By accessing or using the Service you agree to be bound by these Terms. If you disagree with any part of the terms then you may not access the Service.
The author of this data set (hereafter "Author") agrees to the use of this data set by person(s) wishing to use the data (hereafter "User") as stipulated in the Terms and Conditions below.
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Scope of consent
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The User may re-distribute the data to third party without any change or transformation of the data, and may publish new intellectual products (hereafter "Products") based on this data set.
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Conditions for distribution
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The User shall not accept any compensation for the re-distribution of the data of this data set to a third party.
In the event that the User re-distributes the data of this data set to a third party, the same Terms and Conditions apply also to the re-distributed data set. When the User re-distributes the data of this data set to a third party, the User is obliged to inform the third party about the URL of the original data set, the Terms and Conditions of Use, and the fact that the data set is continuously updated by the Author. |
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Use of the latest version
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Unless special reason exists, the User shall use the latest version of this data set.
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Citation policy
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When publishing any Products based on the present data set, it must be clearly stated that the present data set was used.
However, the Author may request the User to delete the citation from the Product. In that case, the User shall comply with the request within reasonable extent. |
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Citation format
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When this data set is referred to in publications, it should, as a general rule, be made in the following format.
Tohjima et al. (2002), Analysis and presentation of in situ atmospheric methane measurements from Cape Ochi-ishi and Hateruma Island, J. Geophys. Res., 107, 4148, DOI:10.1029/2001JD001003.
However, if the citation format is otherwise determined by the submission guidelines of the journal, the journal submission guidelines are to be followed.Tohjima et al. (2016), Continuous observational data of atmospheric CH4 mixing ratios at Cape Ochi-ishi, Ver. x.x (*1), Center for Global Environmental Research, National Institute for Environmental Studies, DOI:10.17595/20160901.004. (Reference date: YYYY/MM/DD)(*2) (*1) The version number is indicated in the name of each data file. (*2) As the reference date, please describe the date you downloaded the files. |
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Utilization reporting
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Re-distribution of the data or release of Products derived from the data set, shall be reported to the Data Provider without delay.
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Error reporting
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Any error in the data set, or the suspicion thereof, should be immediately reported to the Data Provider.
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Disclaimer
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The Author and the Data Provider shall not have any liability or responsibility whatsoever for any damage that may arise from the use of this data set, and the User must not imply that any guarantee is provided by the Author or the Data Provider. Any injury or loss arising from the use of this data set is solely the responsibility of the User.
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Advisory Service
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Advisory service
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If you need scientific advice or expert opinion regarding the contents or scientific validity of this data set or Products derived from it, we can provide an advisory service based on an individual contract, different from the above one.
Depending on the extent of the help required, we can offer collaboration and/or supervision of the work based on the present data set. If you want to use our advisory service, contact the Data Provider. |