The dependence of the beta coefficient of REA system with dynamic deadband on atmospheric conditions |
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Authors: | Grönholm Tiia Haapanala Sami Launiainen Samuli Rinne Janne Vesala Timo Rannik Ullar |
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Institution: | Department of Physical Sciences, University of Helsinki, P.O. Box 64, FIN-00014, Finland. tiia.gronholm@helsinki.fi |
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Abstract: | We simulated the REA system with dynamic deadband to study numerical value and the effect of atmospheric conditions on the empirical constant beta which relates vertical flux to concentration difference between updrafts and downdrafts. We found that the value of beta depends only weakly on the friction velocity and atmospheric stability. In agreement with previous studies, the median value obtained for a system with dynamic deadband proportional to 0.5 times the running mean of the standard deviation of vertical wind speed was beta=0.42+/-0.03. For a single half-hour measurement one has to consider the large uncertainty of +/-0.2. According to our study, the dynamic deadband enables the use of a constant value of beta in flux calculation. |
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Keywords: | Relaxed eddy accumulation Beta coefficient Stability Flux measurement |
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