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| Titel |
Advection: intermittency aspects of CO2 fluxes |
| VerfasserIn |
L. Siebicke, A. Serafimovich, M. Hunner, T. Foken |
| 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 |
250021359
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| Zusammenfassung |
| Horizontal and vertical advection of CO2 was investigated with a focus on high frequency
aspects of horizontal advective fluxes. Measurements were carried out in the framework of
the experiment “ExchanGE processes in mountainous Regions” (EGER) at the FLUXNET
site Waldstein/Weidenbrunnen (DE-Bay), a forest site in the Fichtelgebirge Mountains in
Southern Germany. The setup comprised vertical profiles of wind speed, temperature and
CO2 at two high towers as well as horizontal profiles of wind speed, temperature and CO2 in
the subcanopy. The latter were instrumented with individual closed path infrared gas
analyzers at each sample point in addition to sonic anemometers. The multi-instrument
design yields continuous high frequency time series and thus allows the detailed analysis of
short lived temporal structures not commonly accounted for in advection estimates.
To investigate individual features of the scalar concentration and wind field that
affect the commonly used 30 minute averages of advection, the following temporal
characteristics are studied: stationarity, intermittency, event duration, the effect of
coherent structures on advective fluxes, the sampling bias of 30 minute advection
estimates due to short lived events. Among the spatial characteristics studied are:
structure size and spacing, which can be used as an indication how representative
the signal is for the “control volume”. The study aims to characterize an observed
advection signal as the result of one of the following three situations: a homogeneous
wind field and homogeneous sloping scalar concentration field, stationary in time
for more than 30 minutes versus a dynamic non stationary locally varying scalar
concentration and wind field creating an advection signal due to the asymmetric structure or
occurrence of events versus a combination of both which is assumed to be most
realistic. |
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