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Izaña (Tenerife)
-CO-
| Observation |
| Category |
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Air sampling observation |
| Situation |
: |
ongoing |
| Time zone |
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UTC |
| Sampling |
| Sampling height |
: |
30 |
| Description |
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continuous |
| Sampling and analysis frequency |
: |
one ambient sample every 20 minutes |
| Sampling environment |
: |
The Izaña station is located at 2367 m above see level, on the Island of Tenerife, Spain. The ground in the vicinity around Izaña is loosely covered with light volcanic soil. The vegetation in the surrounding area is sparse, consisting mainly of broom. A belt of pine forest grows between 1000 and 2000 meters a.s.l. During nighttime (20UTC-08UTC), in situ measurements are representative of free troposphere background conditions. This is due to the following facts: a) usually a strong subtropical temperature inversion layer is located at a lower altitude than Izana station; b) Izana station is located on the top of a crest, so during the night period downslope wind produces (by mass conservation) the arrival of free troposphere air to Izana. During daytime, small amounts of air coming from the forest can arrive to the station due to surface upslope wind produced by ground diurnal heating. Apart from this effect, there is no arrival of polluted air from the rest of the island, due to the presence of the strong subtropical temperature inversion layer. |
| Description for sampling analysis |
: |
The general ambient air inlet, which provides ambient air for all instruments that analyze it, is an 8cm inner diameter (ID) stainless steel pipe and has a high flow rate. This inlet is situated on top of the building tower; the height above the ground has changed through the years: 13 m (1984-2000), 8 m (2000- May 2005) and 30 m (from June 2005). Upstream of the GC sample loop (1 ml size), a cryocool trap is used to reduce the dew point of ambient air to -49 ºC. |
| Instrument and Analysis |
| Measurement method |
: |
Gas Chromatography (RGD) |
| Current status and history of instrument |
: |
1998 August - present, GC-RGA3, Trace Analytical |
| Description of instrument |
: |
See references. |
| Calibration |
| Current scale employed in the measurement |
: |
NOAA-2004 Scale |
| Measurement calibration |
: |
A potential response function relative to the working standard is used (so, the response function has two parameters to fit; the fitting is carried out applying least squares after taking logarithm). The working standard is injected every 20 minutes. Every two weeks, the relative potential response function of the instrument is obtained using five WMO standards since March 1999. Before, a variable number (three or four) of WMO standards was used. |
| Scale and calibration(treasability) |
: |
NOAA-2004 Scale.
The working gas tank and the instrument is calibrated every two weeks against five carbon monoxide Izana primary standards (prepared by WMO GAW CO CCL).
On September 2015, a re-submission of the full time series (2008-2014) was performed, because mole fraction was reassigned taking into account the drift of one (CA06946) of the five IZO CO laboratory standards (used since 2009), and the reassignment of mole fraction to the IZO CO old laboratory standards (used in 2008). |
| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
: |
See References. |
| Processing for averaging |
: |
Processing for Hourly Data:
Hourly data are computed averaging the corresponding physical data for valid ambient injections. SD -> standard deviation of the sample (to compute the standard deviation of the mean, SD must be divided by sqrt(ND)).
Processing for Daily Data:
The daily mean for the day "n" is computed averaging the corresponding available hourly means between 20:00 UTC of day "n-1" and 08:00 UTC of day "n" (so, they could be called "daily night means"). As explained in the paragraph "Sampling environment", the atmospheric conditions at the station during such hours are of pure free troposphere. SD: standard deviation of the sample of hourly means (without taking into account the internal SD of each hourly mean). ND: number of hourly means available for computing the daily night mean (max=12).
Processing for Monthly Data:
Monthly data are computed averaging the corresponding daily night means (see paragraph "processing on daily data"). SD: standard deviation of the sample of daily night means (without taking into account the internal SD of each daily night mean). ND: number of valid daily night means used. |
| Data flag |
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No flags are used. Several procedures have been used to identify periods of malfunction of the instrumental system and the associated measurements have been discarded. |
| Data remarks |
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| Other Information |
| Scientific aim |
: |
To determine temporal variability of atmospheric CO at Izaña (North Atlantic free troposphere background conditions): short-term variability, seasonal variability and long-term trend. To provide data to WDCGG as a Global GAW station. |
| Reference |
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Gomez-Pelaez, A. J., Ramos, R., Gomez-Trueba, V., Novelli, P. C., and Campo-Hernandez, R.: A statistical approach to quantify uncertainty in carbon monoxide measurements at the Izaña global GAW station: 2008–2011, Atmos. Meas. Tech., 6, 787-799, doi:10.5194/amt-6-787-2013, 2013
Zellweger, Christoph, et al. (2009), System and Performance Audit of Surface Ozone,Carbon Monoxide, Methane and Nitrous Oxide at the Global GAW Station Izaña, Spain, March 2009, WCC-Empa Report 09/1 |
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| submitted by Izana Atmospheric Research Center,Meteorological State Agency of Spain |
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