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El Tololo
-CO-
| Observation |
| Category |
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Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
: |
UTC |
| Sampling |
| Sampling height |
: |
5 |
| Description |
: |
continuous |
| Sampling and analysis frequency |
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data are continuously recorded with 1 Hz sampling rate. |
| Sampling environment |
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El Tololo is a background station in a pristine arid environment. Local emissions are rare and vegetation is sparse.
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| Description for sampling analysis |
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tubing material: Dekabon/Synflex 1/4" OD; total inlet length approx. 10m; 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).
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| Instrument and Analysis |
| Measurement method |
: |
Cavity ring-down spectroscopy (CRDS) |
| Current status and history of instrument |
: |
May 2013 until now: Picarro Inc., G2401, S/N CFKADS2031 |
| Description of instrument |
: |
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. Thus, no drying is applied prior to analysis and CO dry air mole fractions are determined by application of an empirical humidity correction to the fully unaltered humid gas stream accounting for dilution and pressure broadening effects. The humidity correction function is determined on-site approximately twice a year.
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| Calibration |
| Current scale employed in the measurement |
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WMO CO X2004 |
| Measurement calibration |
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Four calibration tanks are measured automatically every 2 to 9 days. Three of them are tanks purchased from the GAW Central Calibration Laboratory (NOAA ESRL), the mole fractions of the fourth tank are 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 cylinder that is measured every second day for quality control.
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| 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).
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| 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 trace gas mole fractions that are treated as (unknown) sample in a sequence of analyses) measurements, and consistency checks.
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| 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 of background mole fractions in South America |
| Reference |
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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 Direccion Meteorologica de Chile / Swiss Federal Laboratories for Materials Testing and Research |
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