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Concordia, Dôme C
-O3-
| Observation |
| Category |
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Air sampling observation |
| Situation |
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interrupt |
| Time zone |
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Local time +10 |
| Sampling |
| Sampling height |
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5 |
| Description |
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continuous |
| Sampling and analysis frequency |
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Surface ozone data are continuously recorded on a 1-minute basis. |
| Sampling environment |
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These measurements are carried out at the Clean Air Research Observatory , located 700 m SW with respect to the main base and upwind to the prevalent wind direction.
In the Antarctic environment, intrusions of stratospheric air masses, transport of air masses from lower latitudes, depletion processes involving reactive halogen atoms can influence surface ozone variability. In particular, recent studies revealed an unexpected active photochemistry in the Antarctic Plateau leading to the production of elevated surface O3 amounts in the near-surface boundary layer.
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| Description for sampling analysis |
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The main air intake is a passivated steel inlet of 2.2 m length and 12 cm of internal diameter. The air entrance is at 5 m from the ground. A blower maintains the residence time to less than 2 sec along the main sampling head. The circuit to the analyzer and the analyzer itself were heated to reach the optimal operational temperature.
Teflon tubing (1 m long with a diameter of 1/4 inch) is connecting the main sampling head to the ozone analysers.
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| Instrument and Analysis |
| Measurement method |
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Light absorption analysis (UV) |
| Current status and history of instrument |
: |
2005, December - 2010, December: Thermo Environmental Tei 49c (SN: 000687)
2007, December - 2008, November: Dasibi 1108 (back-up analyser, SN: 207)
2010, December - ongoing: Thermo Environmental Tei 49i (SN: CM08460046)
2011, January - ongoing: Dasibi 1108 (back-up analyser, SN: 207) |
| Description of instrument |
: |
Thermo Electron Tei 49c (factory specification):
Zero noise: 0.5 ppb RMS
Lower detectable limit: 1.0 ppb
Zero drift: < 1 ppb/24 hour; < 2 ppb/7 day
Span drift: less than 1% per month (including drift of transducers)
Response time: 20 seconds (10 seconds lag time)
Linearity: ± 1% of full-scale
Thermo Electron Tei 49i (factory specification):
Zero noise: 0.25 ppb RMS (60 second averaging time)
Lower detectable limit: 1.0 ppb
Zero drift: < 1 ppb/24 hour; < 2 ppb/7 day
Span drift: less than 1% per month (including drift of transducers)
Response time: 20 seconds (10 seconds lag time)
Linearity: ± 1% of full-scale
Dasibi 1108 (factory specification) |
| Calibration |
| Current scale employed in the measurement |
: |
Noise: ± 1 ppb
Lower detectable limit: 1.0 ppb
Zero drift: zero
Span drift: less than 1% per month
Response time: 30 seconds (to 95% Full Scale)
Linearity: ± 1 ppb |
| Measurement calibration |
: |
January 2006 - December 2010: IMGC-O3SRP (hosted at INRIM).
January 2011 - ongoing: SRP 15 (hosted at WCC-EMPA) |
| Scale and calibration(treasability) |
: |
Thermo Environmental and Dasibi analysers perform daily zero and span (about 80 ppb, only Thermo Environmental analysers) checks. |
| Data Processing |
| Measurement unit |
: |
On October 2005 (in Italy at the ISAC headquarter) and on December 2007 (at the station), the Thermo 49c (SN: 000687) has been intercompared against the laboratory transfer standard (Dasibi 1008 PC #6506) working at the Mt. Cimone station (GAW code CMN).
On December 2010, the Thermo 49c (SN: 000687)and Thermo 49i (SN: CM08460046)analysers have been intercompared for 3 days at the station by sampling ambient air. The Thermo 49i was intercompared on June 2010 against the laboratory transfer standard (Dasibi 1008 PC #6506) working at the Mt. Cimone station (GAW code CMN).
The analyser Thermo 49i (SN: CM08460046) was checked by factory on November 2009 and September 2010 against the calibrator Tei 49C-PS # 77309-385. The Thermo 49C (SN: 000687)was checked by factory on July 2012 against the calibrator Tei 49C-PS # 77309-385.
During the periods 2007, December - 2008, November and 2011 January - present, a Dasibi 1108 (SN: 207) was also working at the station. Before shipping to Antarctica the Dasibi instrument was intercompared against the laboratory transfer standard (Dasibi 1008 PC #6506) working at the Mt. Cimone station (GAW code CMN).
Moreover, the Dasibi 1108 (SN: 207) was checked by factory on July 2005 and April 2010 against the calibrator Dasibi 5008 # 071-DP.
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| Data processing |
: |
ppb |
| Processing for averaging |
: |
Processing for Hourly Data:
Thanks to satellite connections, surface ozone data are daily sent to ISAC-CNR headquarters for processing. Original 1-minute surface ozone data are daily inspected by operator at ISAC-CNR. Meteorological parameters are used for validation purposes and for rejecting data possibly influenced by station emissions. For Thermo Environmental instruments, internal parameters are also checked for pointing out malfunctioning.
Processing for Daily Data:
Hourly data are obtained averaging 1 minutes mean O3 values.
Processing for Monthly Data:
Daily data are obtained averaging hourly mean O3 values. |
| Data flag |
: |
Monthly data are obtained averaging daily mean O3 values. |
| Data remarks |
: |
No flag applied: unvalid, dubious or calibration data are rejected. |
| Other Information |
| Scientific aim |
: |
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| Reference |
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Investigation of background troposphere variability in Antarctica
Investigation of long-range transport
Investigation of stratospheric intrusion events
Investigation of photochemistry |
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| submitted by National Research Council, Institute of Atmospheric Sciences and Climate |
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