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Minamitorishima
-CO-
| Observation |
| Category |
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Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
: |
Local time +9 |
| Sampling |
| Sampling height |
: |
20 |
| Description |
: |
continuous |
| Sampling and analysis frequency |
: |
Sample air is discretely sampled into the analyzer and analyzed every 10 minutes (Jan. 2010 - present).
Continuous flow of 3.5 liters per minute, data was analyzed every 30 seconds (Jan. 1994 - Dec. 2009). |
| Sampling environment |
: |
The observatory is located on a little isolated island in the western North Pacific, about 2000 km southeast of Tokyo. The observatory is surrounded by insignificant shrubs and grass. |
| Description for sampling analysis |
: |
Air is sampled from a stainless steel intake mounted at a ground height of 20 m on a tower with about 12 liters per minute. The air sample is introduced to the observation system through an inlet line made of stainless steel. The air is dried with an electronic cooler unit, a Perma Pure dryer, and a chemical dryer (Mg(ClO4)2) at a dew-point temperature about 5, -50 and -70 degrees centigrade. The flow rate in the gas analyzer is 0.25 liters per minute. |
| Instrument and Analysis |
| Measurement method |
: |
Gas Chromatography (RGD) |
| Current status and history of instrument |
: |
Jan. 1994 - Dec. 2009 GA-360S HORIBA, Ltd.
Jan. 2010 – present TRA-1 Round Science Inc. |
| Description of instrument |
: |
Measurement range : 20 to 2000 ppb
Lowest detection limit: 1 ppb
Repeatability: ±2 ppb (Standard gas in concentration of 500ppb is measured continuously ten times) |
| Calibration |
| Current scale employed in the measurement |
: |
WMO CO scale |
| Measurement calibration |
: |
The quadratic fitting curve is determined every 8 hours by a set of 4 station working standard gases of CO-in-natural air mixtures in different concentrations. The mole fraction is determined by this fitting curve (Jan. 2010 - present).
The linear fitting curve is determined every 12 hours by CO zero gas and a station working standard gas of CO-in-nitrogen mixtures (Jan. 1994 - Dec. 2009). |
| Scale and calibration(treasability) |
: |
WMO CO scale(Jan.2010 -)
National Standard(Jan.1994 - Dec.2009)
The data during 1994 - 2009 are corrected accoding to the WMO scale
Hierarchy of standards
The laboratory primary standard gases are calibrated by WMO reference standard gases.
The working standard gases in the station are calibrated by the laboratory primary standard gases.
Frequency of calibration and latest calibration
The laboratory primary standard gases are calibrated by WMO reference standard gases at WMO CCL every 3 years.
The latest calibration at CCL was performed in February 2010.
The working standard gases in the station are calibrated by the laboratory primary standard gases before, in, and after use.
Calibration history
Calibration date (Calibration standard)
Jan. 2007 at NOAA (NOAA-GMD/WMO 2000 scale)
Feb. 2010 at NOAA (2004 NOAA/WMO scale) |
| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
: |
The raw data from instrument is collected by the data acquisition system, and stored in the system as every 10 minutes raw data (or 30 seconds mean data, Jan. 1994 - Dec. 2009). CO measurements are checked at the site by an operator every day. All irregular measurements and information are recorded in a log book. Measurement data are transmitted to the headquarters every month and are checked again there. Finally, the measurement data are checked and validated by the contributor at the headquarters. |
| Processing for averaging |
: |
Processing for Hourly Data:
Hourly data are taken from the arithmetic mean of observed data for one hour after the irregular and evident error data are rejected.
Processing for Daily Data:
Daily data are taken from the arithmetic mean of background hourly data.
Processing for Monthly Data:
Monthly data are taken from the arithmetic mean of background hourly data.
For the details of background hourly data, please refer to
http://ds.data.jma.go.jp/gmd/wdcgg/pub/data/documents/JMA_flag.html |
| Data flag |
: |
Hourly data
0-6: no background condition
7: background condition
9: missing
Daily and Monthly data
2: no valid hourly data
3: valid
9: missing
For the details, please refer to http://ds.data.jma.go.jp/gmd/wdcgg/pub/data/documents/JMA_flag.html |
| Data remarks |
: |
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| Other Information |
| Scientific aim |
: |
To provide critical data for research and study to reveal long term trends at the western North Pacific. |
| Reference |
: |
Tsutsumi, Y., K. Mori, M. Ikegami, T. Tashiro, K. Tsuboi, (2006) Long-term trends of greenhouse gases in regional and background events observed during 1998-2004 at Yonagunijima located to the east of the Asian continent. Atmospheric Environment, 40, 5868-5879.
JMA, Observation method of the greenhouse gas
http://www.data.jma.go.jp/gmd/env/ghg_obs/en/ |
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| submitted by Japan Meteorological Agency |
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