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Hohenpeissenberg
-CO-
| Observation |
| Category |
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Air sampling observation |
| Situation |
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ongoing |
| Time zone |
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Local time +1 |
| Sampling |
| Sampling height |
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18 |
| Description |
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continuous |
| Sampling and analysis frequency |
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1.) NDIR: continuous with max. time resolution of 20 min.
2.) resonance fluorescence: continuous with max. time resolution of 1 minute
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| Sampling environment |
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Hohenpeissenberg is an isolated mountain at 985 m a.s.l., 40 km north of Zugspitze (Alps) in a hilly area. The mountain rises 300m above the surrounding area, which is populated to an extent typical for central Europe and partly covered with meadows (~ 70%) and forests (~ 30%). The Meteorological Observatory situated on top of Hohenpeissenberg mountain has a long history of meteorological and climatological observations (since 1781) and is well-known for its long ozone record.
Main sources of CO are the oxidation of methane and other hydrocarbons and direct combustion processes. Main sink is reaction with OH radical. Because of the long life time (weeks to months) CO is a tracer for anthropogenic influences of the atmosphere and an indicator for the origin of enhanced ozone mixing ratios in the troposphere. It has an indirect influence on the greenhouse effect and is involved in tropospheric ozone formation as the "easiest hydrocarbon". |
| Description for sampling analysis |
: |
1.) Continuous CO NDIR / GFC analyser.
Inlet line consists of PFA-Teflon and is heated to 3°C above ambient air temperature to avoid condensation. For zero air, ambient air with removed CO by a Pd-catalyst is used. Measuring cycle is 10 minutes ambient air, 10 minutes zero air. This procedure excludes the well known H2O interference typical for IR analysers. The experimentally identified LDL with this set-up is about 10 ppb.
2.) Since April 2004: Continuous CO resonance fluorescence analyser.
Same inlet line. Time resolution: 1 minute ; lower detection limit : 1 ppb. Air is humidified by means of a Nafion dryer.
Since June 2004 the resonance fluorescence monitor is the "master instrument" and the NDIR monitor serves as backup instrument. |
| Instrument and Analysis |
| Measurement method |
: |
1.) NDIR
2.) resonance fluorescence
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| Current status and history of instrument |
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1.)Jan 1995 - ongoing: TE 48S #48S-50873-286
Thermo Environmental Instruments Inc.
2.)Jun 2004 - ongoing: AL 5001 #142 ; Aero Laser GmbH, Germany.
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| Description of instrument |
: |
1.) NDIR: Infrared absorption instrument Thermo Instruments 48 S (especially for low ambient mixing ratios). Improved detection limit by switching every ten minutes between ambient air and zero air according the paper of Parrish et al.(Environ.Sci.Technol.,28,1615-1618, 1994).
Linear over the whole measurement range from LDL to 1ppm verified by multi point calibrations twice a year.
2.) R.F.(VUV): Resonance flourescence instrument Aero Laser 5001. LDL is at 1ppb, resolution also at 1ppb by a time resolution about 1 minute. Linear over the whole measurement range from LDL to 2ppm verified by multi point calibrations twice a year.
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| Calibration |
| Current scale employed in the measurement |
: |
GAW/CCL CO standard (based on WMO-2004 CO scale), audits by WCC in 1999, 2006 and 2011, all with excellent agreement.
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| Measurement calibration |
: |
for NDIR-Analyser:
1/95-4/96 : Calibration and zero check was carried out twice a week.
5/96-9/97 : Every 5 minutes switch between zero and measuring mode.
Since 10/97: Every 10 minutes switch between zero and measurement mode, calibration once a week.
Certified CO in N2 in cylinders and dynamic dilution with synthetic air is used for calibration. For zero measurement ambient air after removal of CO by oxidation with Pd-catalyst (150 °C) is used.
Serves as backup instrument. Continuous intercomparison with resonance fluorescence method.
for resonance fluorescence:
since 04/04 : Calibration is carried out once a day and zero check every 11 hours.
since 04/05 : Calibration and zero check are carried out every 11 hours. |
| Scale and calibration(treasability) |
: |
Scale refers to the WMO-2004 CO scale. Last audit was in June 2011 with excellent agreement.
Last round robin with 5 CMDL standards took place in Nov. 2005 with excellent agreement (mean deviation < 1.7%).
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| Data Processing |
| Measurement unit |
: |
ppb |
| Data processing |
: |
The data acquisition system provides one minute mean raw data. Calibration factors and data protocols are used to convert raw data into calibrated data. Invalid data caused by local impact, malfunction or other effects were recognized by comparison/correlation with other trace substances and meteorological data or with information from the station logbook and were rejected.
For NDIR analyser: From these selected data 20 min mean values are generated (difference between 5 min zero - 10 min measurement - 5 min zero) with number of data being more than 10 (more than 5 in zero mode and more than 5 in measurement mode).
For resonance flourescence (RF) analyser: 10 min mean values are generated by calculating the arithmetic mean of the remaining data with number of data being more than 6. |
| Processing for averaging |
: |
Processing for Hourly Data:
NDIR: Take the arithmetic mean of selected 20 min mean data with the number of data being more than 1.
RF : Take the arithmetic mean of respective one minute mean validated data with the number of data more than 40.
Processing for Daily Data:
Daily data take the arithmetic mean of respective hourly data with the number of hourly data more than 16.
Processing for Monthly Data:
Monthly data take the arithmetic mean of respective hourly data with the number of daily data more than 20 (for February more than 19, respectively).
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| Data flag |
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Only validated data are sent to WDCGG. |
| Data remarks |
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| Other Information |
| Scientific aim |
: |
Long term trend, tracer for anthropogenic impact, interpretation with respect to ozone formation. |
| Reference |
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Gilge, S., C. Plass-Duelmer, W. Fricke, A. Kaiser, L. Ries, B. Buchmann, and M. Steinbacher, Ozone, carbon monoxide and nitrogen oxides time series at four alpine GAW mountain stations in central Europe, Atmos. Chem. Phys., 10, 12295–12316, 2010 (doi:10.5194/acp-10-12295-2010).
Stefan Gilge, Measurement of reactive Trace Gases at Hohenpeissenberg as Part of GAW, in „The German Contribution to the WMO/GAW Program: Upon the 225th anniversary of GAW Hohenpeissenberg Observatory, ed. W.Frick, GAW Report 169, 2006
http://www.dwd.de/gaw
Gilge, S., Quality Assurance of long-term CO Measurements, Poster, Joint WMO/ GAW-ACCENT Workshop on the Global Tropospheric Carbon Monoxide Observation System, Quality Assurance and Applications, 24 26 Oktober 2005, EMPA Dbendorf, Switzerland |
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| submitted by Meteorological Observatory Hohenpeissenberg, German Meteorological Service |
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