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| Titel |
Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland |
| VerfasserIn |
F. Bocquet, D. Helmig, B. A. Dam, C. W. Fairall |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 4, no. 10 ; Nr. 4, no. 10 (2011-10-25), S.2305-2321 |
| Datensatznummer |
250002125
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| Publikation (Nr.) |
 copernicus.org/amt-4-2305-2011.pdf |
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| Zusammenfassung |
| A multi-step procedure for investigating ozone surface fluxes over polar snow
by the tower gradient method was developed and evaluated. These measurements
were then used to obtain five months (April–August 2004) of turbulent ozone
flux data at the Summit research camp located in the center of the Greenland
ice shield. Turbulent fluxes were determined by the gradient method
incorporating tower measurements of (a) ozone gradients measured by
commercial ultraviolet absorption analyzers, (b) ambient temperature
gradients using aspirated thermocouple sensors, and (c) wind speed gradients
determined by cup anemometers. All gradient instruments were regularly
inter-compared by bringing sensors or inlets to the same measurement height.
The developed protocol resulted in an uncertainty on the order of 0.1 ppbv
for 30-min averaged ozone gradients that were used for the ozone flux
calculations. This protocol facilitated a lower sensitivity threshold for the
ozone flux determination of ∼8 × 10−3μg m−2 s−1, respectively ∼0.01 cm s−1 for
the ozone deposition velocity for typical environmental conditions
encountered at Summit. Uncertainty in the 30-min ozone exchange measurements
(evaluated by the Monte Carlo statistical approach) was on the order of
10−2 cm s−1. This uncertainty typically accounted to
~20–100% of the ozone exchange velocities that were determined.
These measurements are among the most sensitive ozone deposition
determinations reported to date. This flux experiment allowed for
measurements of the relatively low ozone uptake rates encountered for polar
snow, and thereby the study of their environmental and spring-versus-summer
dependencies. |
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