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Pha Din
-CO-
| Observation |
| Category |
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Air sampling observation |
| Situation |
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ongoing |
| Time zone |
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UTC |
| Sampling |
| Sampling height |
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12 |
| Description |
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continuous |
| Sampling and analysis frequency |
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Data are continuously recorded with 1 Hz sampling rate. |
| Sampling environment |
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Pha Din is located on a hill in north-western rural Viet Nam above the surrounding forests.
Population: No residents at the station except for the custodians. No relevant residential areas within 10-20 km, except for sparse individual farm houses. The closest farm house is located in 1 km distance in NE direction.
Land cover: Mountain hill area covered with forest. The station itself is above the canopy.
Possible influence of local and regional emissions: Occasional corn plant burning in March and April. Staff housing (gas cooking, electrical heating, occasional trash burning) is at the station. No coal power plants and other industrial activities in the region.
Prevailing wind directions: NE in winter and SW in summer.
Temperature: 25-30 ˚C in summer and down to 3 ˚C in winter. No snow or ice in winter.
Rainfall and humidity: The site is in clouds a considerable fraction of the year with a correspondingly high relative humidity all year long.
Access: Pha Din is reachable all year long via a paved mountain road (8 h by car from Ha Noi city via Son La). After heavy rainfalls the roads may be blocked due to landslides.
Facilities: The station represents a Level 3 NHMS meteorological station since September 2011 provid-ing manual readings every 6 hours for wind and wind speed. The laboratory building provides air-conditioned laboratory space and also basic accommodation for station operators and guest research-ers. The station is permanently occupied with 3 staff persons.
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| Description for sampling analysis |
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tubing material: Dekabon/Synflex 1/4" OD; total inlet length approx. 21m; flow rate into lab: 5 lpm; no drying prior to analysis; dry air mole fractions are determined by applying an empirical humidity correction (see below). |
| Instrument and Analysis |
| Measurement method |
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Cavity Ringdown Spectroscopy |
| Current status and history of instrument |
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February 2014 until now: Picarro Inc., G2401, S/N CFKADS2028 |
| Description of instrument |
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CO observations are performed with a commercially available instrument (Picarro Inc., G2401) based on the Wavelength-Scanned Cavity Ringdown Spectroscopy technique coupled to a custom-built calibration unit. Along with CO, the instrument is also capable to measure CO2, CH4 and H2O. Thus, the CO data can be corrected for interferences of water vapor. Therefore, no drying is applied prior to analysis and CO dry air mole fractions are determined by application of an empirical humidity correction to analysis data of the fully unaltered humid gas stream accounting dilution and pressure broadening effects. |
| Calibration |
| Current scale employed in the measurement |
: |
WMO CO X2004 |
| Measurement calibration |
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Four calibration tanks are measured every 3 to 6 days. Two of them are tanks purchased from and pre-pared by the GAW Central Calibration Laboratory for CO (NOAA ESRL). The other two calibration gas-es are prepared by Empa (Switzerland) and their mole fractions were determined by the GAW World Calibration Centre for CH4, CO2, CO and surface O3 (WCC-Empa). WCC-Empa also assigned the mole fractions of an additional target cylinders that is measured every 25 hours for quality control. |
| Scale and calibration(treasability) |
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The analyzer is regularly calibrated with four reference gases. All assigned mole fractions are reported on the WMO CO X2004 scale. The quality of the calibration is verified with a fifth reference gas (target cylinder). |
| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
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Quality assurance procedures involve time series plots, target tank (i.e. cylinders containing natural air with assigned gas mole fractions that are treated as (unknown) sample in a sequence of analyses) measurements, evaluation of the evolution of the instrument sensitivity, and consistency checks. The measurements were made in humid air, and a water vapour correction was applied. |
| Processing for averaging |
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Processing for Hourly Data:
high-resolution data are aggregated to 1min averages before hourly averages are calculated. Thus, ND (the number of detections) refers to the number of available 1min averages within the respective hour.
Processing for Daily Data:
hourly averages are aggregated to daily means. Thus, ND (the number of detections) refers to the number of available hourly averages within the respective day.
Processing for Monthly Data:
daily data are aggregated to monthly means. Thus, ND (the number of detections) refers to the number of available daily averages within the respective month.
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| Data flag |
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| Data remarks |
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| Other Information |
| Scientific aim |
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Long-term trend determination of background mole fractions in rural Vietnam. Influence of large-scale biomass burning on the level of greenhouse gases in rural Vietnam. |
| Reference |
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For a short summary see Trinh Lan Phuong and Duong Hoang Long, Greenhouse gases measurements in Viet Nam, in Asia-Pacific GAW on Greenhouse Gases Newsletter vol 5, 33 - 38, 2014. available at http://www.wmo.int/pages/prog/arep/gaw/documents/The_5th_Asia_Pacifi_Newsletter_on_Greenhouse_Gases.pdf.
The observations are supported by the Federal Office of Meteorology and Climatology MeteoSwiss through the project Capacity Building and Twinning for Climate Observing Systems (CATCOS) between the Swiss Agency for Development and Cooperation (SDC) and MeteoSwiss.
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| submitted by Swiss Federal Laboratories for Materials Testing and Research / Vietnamese National Hydrometeorological Service |
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