Open AccessStability dependence of the relaxed eddy accumulation coefficient for various scalar quantities
Author(s) -
Ammann C.,
Meixner F.
Publication year - 2002
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2001jd000649
Subject(s) - dimensionless quantity , scalar (mathematics) , physics , stability (learning theory) , thermodynamics , mechanics , meteorology , statistical physics , mathematics , geometry , machine learning , computer science
The coefficient b of the relaxed eddy accumulation (REA) technique was investigated by simulation studies using extensive high‐resolution eddy correlation data sets of three different scalar quantities: the air temperature and the concentrations of CO 2 and H 2 O. Measurements were performed in June–July 1995 over a senescent cereal field in the Rhineland‐Palatinate region of southwestern Germany. The wide range of stability conditions during the experiment made it possible to describe the coefficient b as a function of the dimensionless stability parameter z/L within the framework of the Monin‐Obukhov similarity theory. In good agreement with previous publications, a constant value of about 0.56 was obtained for unstable and near‐neutral conditions if no dead band applied. For stable conditions, however, a significant increase with stability was observed which could be well described by a logarithmic functional relationship between b and z/L . By additional dead‐band simulation studies the relationship was extended to variable dead‐band widths. The observed dependency on z/L is interpreted in relation to the bivariate joint frequency distribution of the vertical wind speed and the scalar quantity.