Modelling the Interaction Between a River Surface and the Atmosphere at the Bottom of a Valley |
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Authors: | Daniel P Bitencourt Otávio C Acevedo |
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Institution: | 1. Funda??o Jorge D. Figueiredo de Seguran?a e Medicina do Trabalho, Rua Silva Jardim, n. 213, 88020-200, Florianópolis, SC, Brazil 2. Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
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Abstract: | The role of a river of small dimensions in driving the surface exchange of sensible and latent heat fluxes at the bottom of
a valley is investigated using large-eddy simulation (LES). Simulations were performed using different valley topographies,
river widths and large-scale wind speed and direction. In all cases, the river acted as a sink of both sensible and latent
heat during daytime. Despite the general agreement concerning the flux direction above the river surface, specific differences
exist between the simulations. The topography enhances the wind divergence caused by the river, and the larger negative surface
fluxes above the river occur when there are no slopes, a consequence of larger wind speeds above the river. For large-scale
winds aligned with the valley axis, the surface fluxes depend on the large-scale wind speed, but this dependence is reduced
if the large-scale wind is perpendicular to the valley axis. There is a minimum of temperature and a maximum of specific humidity
above the river surface. The scalar budgets show that sensible heat flux converges above the river, being balanced by the
warm air subsidence at the centre of the valley. Latent heat fluxes, on the other hand, converge above the river surface,
and they are balanced by the horizontal advection of humidity towards the river margins. |
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Keywords: | Large-eddy simulation Latent heat flux River Sensible heat flux Valley |
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