engleski

Study of a sea breeze case through momentum, temperature and turbulence budgets

A simulation with the Meso-NH model over the island of Mallorca has been made in a case of synoptic high-pressures (June 5th, 2010) that allowed the development of sea breezes (SB) in the three main basins of the island. The results compare well with the available observations and are qualitatively very close to a previous idealized study with no synoptic forcing made by Ramis and Romero in 1995. The temporal and spatial structure of the SB on the southeastern basin is analyzed with the use of the budgets of momentum, temperature and turbulence kinetic energy provided by the numerical model. Five stages of evolution from before dawn to after sunset are discussed, identifying the principal physical mechanisms on play. The morning land heating warms the land and the air over it until an air temperature gradient is created and a marine flow accelerates inland, dragged by turbulence at the low layers. The upper part of the inland current and the layers just above are dominated by compensatory motions, opposing to corresponding pressure gradient at these levels. These mechanisms act during the duration of the phenomenon, with significant impact of the local topography, decreasing in intensity as sunset approaches. This relatively simple case has been used to check the goodness of two simple analytical models of the SB, that perform relatively well as they use the turbulence as a surrogate of the missing advection terms in the layers above 200 m. These models are formulated here in a more consistent manner in the turbulence parametrization than the original propositions.

Mediterranean Sea; small scale processes; turbulence; boundary layer; diurnal effects; sea breezes

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