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Titel |
Eddy covariance fluxes of the NO-NO2-O3 triad above a spruce forest canopy in south-eastern Germany. |
VerfasserIn |
A. Tsokankunku, Z. Zhu, F. X. Meixner, T. Foken, M. O. Andreae |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250027495
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Zusammenfassung |
We investigated the diel variability of the eddy covariance fluxes of the NO-NO2-O3 triad
above a spruce forest canopy at the "Weidenbrunnen" research site (Fichtelgebirge,
Germany). Measurements were part of the EGER project (ExchanGE processes in
mountainous Regions), which focuses on the role of process interactions among the different
scales of soil, in-canopy and atmospheric exchange processes of reactive and non-reactive
trace gases and energy.
The eddy covariance platform was at the top of a 32 m high tower (50Ë 08’31” N, 11Ë
52’1”E, elevation 755 m.a.s.l). The eddy covariance system consisted of a CSAT3 sonic
anemometer and a high speed, high resolution NO-NO2two channel chemiluminescence
analyzer (Ecophysics CLD 790 SR2). A solid-state blue-light photolytic converter was
connected to the NO2 channel of the analyzer just behind the sample inlet. Ambient NO and
NO2 mixing ratios were sampled via 52 m long tubes with the instrument itself located in a
temperature-controlled container at the ground. The NO-NO2 analyzer was operated at 5 Hz.
Additionally we measured eddy covariance fluxes of CO2 and H2O. An infrared
absorption-based analyzer (LI-7000) was used to sample CO2 and H2O mixing ratios,
and a fast solid-phase chemiluminescence ozone analyzer (GFAS) was deployed
to measure O3 mixing ratios. All trace gas inlets were situated at 32.5 m, 20 cm
below the path of the sonic anemometer. The 32m inlet of an independent NO,
NO2, and O3 concentration profile measuring system was used as the calibration
source for the fast ozone analyzer and the two channel NO-NO2chemiluminescence
analyzer.
Preliminary results show that NO and NO2advection plays a big role in the magnitude
and direction of the fluxes at the site. The main source of the advection is a busy country road
situated about 2 km west of the site. CO2 fluxes were also influenced by advection. Extended
periods of stationarity usually occurred on Sundays when the amount of traffic was
significantly lower. During the "golden days period" (29 June – 3 July 2008), there was
mainly downward directed NO fluxes (within the margin of error). However there is also
evidence of NO leaving the canopy in some instances. NO and NO2 fluxes ranged between
+1.5 and -1.5 nmol m-2 s-1 (±45 ngNO m-2 s-1 and ±70 ngNO2 m-2 s-1). |
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