A SIMPLE FORMULA FOR ATTENUATION OF EDDY FLUXES MEASURED WITH FIRST-ORDER-RESPONSE SCALAR SENSORS |
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| Authors: | T W HORST |
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| Institution: | (1) National Center for Atmospheric Research, Boulder, CO, USA |
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| Abstract: | A simple formula, (1 + (2 fm c) )-1,is proposed to estimate the attenuation of a scalar flux measurement made by eddy-correlation using a fast-response anemometer and a linear, first-order-response scalar sensor with a characteristic time constant c.In this formula, =7/8 for neutral and unstable stratification within the surface-flux layer and =1 both within the convective boundary layer (CBL) and for stable stratification in the surface layer.fm is the frequency of the peak of the logarithmic cospectrum and can be estimated from fm = nm  /z, where z is the measurement height and is thewind speed at that height. The dimensionless frequency at the cospectral maximum nm is estimated here from observations of its behavioras a function of atmospheric stability, z/L within the surface layeror z/zi within the CBL, where L is the Obukhov stability length and zi is the depth of the CBL. The predicted dependence of flux attenuation on measurement height is discussed. |
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