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Boundary layer budgets for regional estimates of scalar fluxes
Author(s) -
DENMEAD O.T.,
RAUPACH M.R.,
DUNIN F.X.,
CLEUGH H.A.,
LEUNING R.
Publication year - 1996
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.1996.tb00077.x
Subject(s) - convective boundary layer , scalar (mathematics) , boundary layer , flux (metallurgy) , environmental science , mixed layer , atmospheric sciences , radiative flux , planetary boundary layer , convection , surface layer , potential temperature , inversion (geology) , radiative transfer , meteorology , mechanics , mathematics , physics , geology , geometry , layer (electronics) , materials science , geomorphology , quantum mechanics , structural basin , metallurgy , composite material
The paper considers the theory and application of budget techniques for regional scalar flux estimation using the daytime convective boundary layer (CBL) and the nocturnal boundary layer (NBL). CBL techniques treat the well mixed layer of air between heights of, say, 100 m and 1000 m as an integrator of surface fluxes along the path of a column of air moving over the landscape. They calculate the average surface flux from the scalar concentration in and above the mixed layer, and the CBL height. The flux estimates are averaged over regions of 10–10 4 km 2 extending 10 to 100 km upwind. An integral form of the CBL budget is used to estimate daily regional rates of CO 2 uptake and evaporation from three data sets. There was plausible agreement between the estimates and locally measured fluxes. CBL budgets have great potential for estimating regional scalar fluxes, but there is an urgent need for validation through direct measurements of fluxes and budget parameters. NBL budgets are useful when low‐level, radiative inversions inhibit vertical mixing. Surface scalar fluxes can then be estimated from the rate of concentration change below the inversion. An example application for estimating the nocturnal CO 2 flux is given. While simple in concept, NBL budgets are more difficult to apply in practice because of the unpredictability of the depth of the layer and sometimes, its absence altogether. On the other hand, the depth of the atmospheric mixing chamber is better defined, few assumptions are required and the concentration changes usually will be larger and hence more easily detectable than in CBL budgetting.