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| Titel |
Pressure correction to the long-term measurement of carbon dioxide flux |
| VerfasserIn |
Junhui Zhang, Xuhui Lee, Guozheng Song, ShiJie Han |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048266
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| Zusammenfassung |
| Fluctuations in atmospheric CO2 density can arise from static pressure fluctuations but their
effect on the long-term eddy covariance (EC) CO2 flux measurement is poorly
known.
Accounting for the WPL density effects(density effects due to heat and water-vapor
transfer) and ignoring the advection terms, Massman and Lee (2002) showed that NEE (net
ecosystem exchange) is expressed with four terms. The first term is the storage flux, the
second term is the eddy flux, the third term is the traditional WPL correction term and the last
term is the density correction arising from pressure fluctuations. But, the last term, is usually
omitted in EC studies.
In this paper, we report the results of a 1-year direct measurement of the static pressure
fluctuations and the velocity–pressure covariance over a mixed forest in Northeast
China. The results show that the pressure–vertical velocity covariance was primarily
controlled by friction velocity and air stability. Without the pressure correction, the
open-path EC measurement of the night-time ecosystem respiration was biased low and
that of the daytime photosynthetic CO2 uptake was biased high. Over the 1-year
measurement period, the cumulative pressure correction was 40gCm-2, which was about
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