Land and sea breezes are wind and weather phenomena associated with coastal areas. A land breeze is a breeze blowing from land out toward a body of water. A sea breeze is a wind blowing from the water onto the land. Land breezes and sea breezes arise because of differential heating between land and water surfaces. Land and sea breezes can extend inland up to 100 mi (161 km) or manifest as local phenomena that quickly weaken with a few hundred yards of the shoreline. On average, the weather and cloud effects of land and sea breezes dissipate 200 mi (328 kph) inland from the coast.
Because water has a much higher heat capacity that do sands or other crustal materials, for a given amount of solar irradiation (insolation), water temperature will increase less than land temperature. Regardless of temperature scale, during daytime, land temperatures might change by tens of degrees, while water temperature change by less than half a degree. Conversely, water's high heat capacity prevents rapid changes in water temperature at night and thus, while land temperatures may plummet tens of degrees, the water temperature remains relatively stable. Moreover, the lower heat capacity of crustal materials often allows them to cool below the nearby water temperature.
Air above the respective land and water surfaces is warmed or cooled by conduction with those surfaces. During the day, the warmer land temperature results in a warmer (therefore less dense and lighter) air mass above the coast as compared with the adjacent air mass over the surface of water. As the warmer air rises by convection, cooler air is drawn from the ocean to fill the void. The warmer air mass returns to sea at higher levels to complete a convective cell. Accordingly, during the day, there is usually a cooling sea breeze blowing from the ocean to the shore. Depending on the temperature differences and amount of uplifted air, sea breezes may gust 150 mph (242 kph). The greater the temperature differences between land and sea, the stronger the land breezes and sea breezes.
After sunset, the air mass above the coastal land quickly loses heat while the air mass above the water generally remains much closer to it's daytime temperature. When the air mass above the land becomes cooler than the air mass over water, the wind direction and convective cell currents reverse and the land breeze blows from land out to sea.
Because land breezes and sea breezes are localized weather patterns, they are frequently subsumed into or overrun by large-scale weather systems. Regardless, winds will always follow the most dominant pressure gradient.
The updraft of warm, moist air from the ocean often gives rise to daytime cloud development over the shoreline. Glider pilots often take advantage of sea breezes to ride the thermal convective currents (sea breeze soaring). Although most prevalent on the sea coastline, land breezes and sea breezes are also often recorded near large bodies of water (e.g., the Great Lakes). In general, land breezes and sea breezes result in elevated humidity levels, high precipitation, and temperature moderation in coastal areas.
See also Adiabatic heating; Clouds and cloud types; Convection (updrafts and downdrafts); Seasonal winds; Weather forecasting methods
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