Variance Method to Determine Turbulent Fluxes of Momentum And Sensible Heat in The Stable Atmospheric Surface Layer |
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Authors: | Email author" target="_blank">H?A?R?De BruinEmail author O?K?Hartogensis |
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Institution: | (1) Meteorology and Air Quality Group, Wageningen University, Duivendaal 2, 6701, AP, Wageningen, The Netherlands |
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Abstract: | Evidence is presented that in the stable atmospheric surface layer turbulent fluxes of heat and momentum can be determined
from the standard deviations of longitudinal wind velocity and temperature, σ u and σ T respectively, measured at a single level. An attractive aspect of this method is that it yields fluxes from measurements
that can be obtained with two-dimensional sonic anemometers. These instruments are increasingly being used at official weather
stations, where they replace the standard cup anemometer–wind vane system. With methods such as the one described in this
note, a widespread, good quality, flux network can be established, which would greatly benefit the modelling community. It
is shown that a ‘variance’ dimensionless height (ζ σ) defined from σ u and σ T is highly related to the ‘conventional’ dimensionless stability parameter ζ=z/L, where z is height and L is the Obukhov length. Empirical functions for ζ σ are proposed that allow direct calculation of heat and momentum fluxes from σ u and σ T. The method performs fairly well also during a night of intermittent turbulence. |
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Keywords: | CASES-99 Sonic anemometers Stable surface layer Variance method |
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