Making simplifying assumptions and applying the principles of conservation of energy and momentum, he found that the speed of a density current should depend only on the density (or temperature) difference and the depth of the two fluids. The theory of density currents was developed by T. Behind the head is a region of turbulent mixing between the warm and cold air.ĭensity currents are found in all sorts of circumstances: oil spills and airborne powder avalanches are also density currents. Density currents have a sharp leading edge, called a "head", where the air ascends rapidly. ![]() Most sharp atmospheric fronts, including land breezes, sea breezes, and coastal fronts, are density currents. As a result, a pronounced diurnal cycle in wind speed and direction develops. Near the warm edge of the temperature gradient there is convergence, causing the temperature gradient to increase on the cold side there is divergence, and the temperature gradient weakens. ![]() The air that feels this pressure force accelerates, driving a wind blowing from cold to warm air. It is this movement of warm and cool air that creates a sea breeze The opposite happens at night when the surface of land cools. As the warm air rises, cooler air from over the ocean moves over land to take its place. Warm air rises as it is less dense than cooler air. sea breeze circulation, land breeze circulation. Sea breezes occur on summer days because land heats up faster than the sea. Where a temperature gradient exists, a pressure gradient is present also where the temperatures are uniform, no pressure gradient is found. In general, these circulations are too small to be influenced significantly by Coriolis. Then, by heating some air near the surface, a zone of temperature gradient near the surface forms separating warm air from cold air. Imagine an initially uniform temperature and pressure distribution. The front is a consequence of the response of the flow to heating. A sea breeze develops a few hours after sunrise, continues during the daylight hours, and dies down after sunset.
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