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| Titel |
Determining the sea-air flux of dimethylsulfide by eddy correlation using mass spectrometry |
| VerfasserIn |
B. W. Blomquist, B. J. Huebert, C. W. Fairall, I. C. Faloona |
| 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 ; 3, no. 1 ; Nr. 3, no. 1 (2010-01-08), S.1-20 |
| Datensatznummer |
250000810
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| Publikation (Nr.) |
 copernicus.org/amt-3-1-2010.pdf |
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| Zusammenfassung |
| Mass spectrometric measurement of DMS by atmospheric pressure ionization with
an isotopically labeled standard (APIMS-ILS) is a sensitive method with
sufficient bandpass for direct flux measurements by eddy correlation. Use of
an isotopically labeled internal standard greatly reduces instrumental drift,
improving accuracy and precision. APIMS-ILS has been used in several recent
campaigns to study ocean-atmosphere gas transfer and the chemical budget of
DMS in the marine boundary layer. This paper provides a comprehensive
description of the method and errors associated with DMS flux measurement
from ship platforms. The APIMS-ILS instrument used by most groups today has a
sensitivity of 100–200 counts s−1 pptv−1, which is shown to be
more than sufficient for flux measurement by eddy covariance. Mass spectral
backgrounds (blanks) are determined by stripping DMS from ambient air with
gold. The instrument is found to exhibit some high frequency signal loss,
with a half-power frequency of ≈1 Hz, but a correction based on an
empirically determined instrument response function is presented. Standard
micrometeorological assumptions of steady state and horizontal uniformity are
found to be appropriate for DMS flux measurement, but rapid changes in mean
DMS mixing ratio may serve as a warning that measured flux does not represent
the true surface flux. In addition, bias in surface flux estimates arising
from the flux divergence is not generally significant in the surface layer,
but under conditions of lowered inversion and high flux may become so. The
effects of error in motion corrections and of vertical motion within the
surface layer concentration gradient are discussed and the estimated maximum
error from these effects is ≤18%. |
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