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Detection of surface heterogeneity in eddy covariance data

Deckert, Rudolf (2012) Detection of surface heterogeneity in eddy covariance data. EGU General Assembly 2012, VIenna.

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Abstract

Upwind-surface heterogeneity can induce instationarity into ground-based eddy covariance (EC) measurements, complicating the interpretation of vertical turbulent flux in terms of surface exchange. A heterogeneity-detection scheme is presented and tested for the case of an abrupt spacial change in land use; a paved surface, rectangular and large, embedded into green grassland. The measuring mast stands at the downwind shorter edge of the rectangular, making an ultrasonic anemometer and a Krypton hygrometer subject to fetch fluctuations from deviations in wind direction. The EC method requires a high-frequency time series of usually half an hour length to produce a single estimate of vertical turbulent flux. The detection scheme is based on binning an individual time series according to instantaneous wind direction, that is, fetch length; one bin tending to be more strongly affected by the grassland than the other. Taking into account autocorrelation, a resampling method establishes a suitable p-value for testing the bin difference. The results are in accordance with both appropriate statistical analyses of the 40 pooled times series and the physical setting of paved surface versus grassland.

Document Type:Conference or Workshop Item (Speech)
Title:Detection of surface heterogeneity in eddy covariance data
Authors:
AuthorsInstitution or Email of Authors
Deckert, Rudolfrudolf.deckert@dlr.de
Date:23 April 2012
Keywords:eddy covariance heterogeneity instationarity
Event Title:EGU General Assembly 2012
Event Location:VIenna
Event Type:international Conference
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:other
HGF - Program Themes:other
DLR - Research area:Aeronautics
DLR - Program:L - no assignement
DLR - Research theme (Project):L -- no assignement
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Dr. Rudolf Deckert
Deposited On:16 Jul 2012 12:35
Last Modified:12 Dec 2013 21:42

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