Hidrodinâmica da Baía do Lobito. Parte I - Correntes de maré

Resumo

This paper describes the study of tidal currents in Lobito Bay, Angola, using a fine mesh model for the interior of the Bay embedded in a larger scale model for the adjacent continental region, in order to impose the tide from the FES2004 model results. A 2D model integrated vertically was used to calculate the tidal flow and a baroclinic 3D model to study the effect of wind and thermohaline stratification. This article - Part I of the work – describes the tidal flow: transient flow, residual flow and the contribution of the tide to the residence time. The results of the model are validated by comparing the calculated levels with tidal levels data reconstituted from harmonic analysis of measured levels within the Bay. The model shows very low speeds, with transient speeds of the order of cm/s and residual speeds of the order of mm/s. Residual flow due to the tide is dominated by two large eddies, occupying each of them about half the bay. The measured and calculated levels are similar, showing that the imposed tide condition (FES2004) on the model boundary is adequate and that the tide propagation inside the bay is represented correctly. Excessive residence times - of the order of months - obtained in simulations suggest that the stratification dominate bay water renewal. Indeed, this is a conclusion of Part II of this work.