Sea Breeze: Causes, Diagram and Effects

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What is a sea breeze?

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A sea breeze is a very cool moisture-laden that blows from the sea during the day towards the land where it is low-pressure. A sea breeze is a very gentle breeze whose velocity reaches its maximum in the daytime; this ranges between 6-50 km per hour in the afternoon. It is important here to take note of the low-pressure condition of the land which is caused by the heating effect of the sun. During the day time, the land gets heated up more quickly than the sea. The heated air expands becomes lighter and rises thereby creating a region of low-pressure. At this time, the sea remains comparatively cooler with higher pressure, therefore the sea breeze automatically blows from the sea to replace the warm rising air on the land.

Causes of sea breeze

The sea breeze is caused by differences in air pressure created due to the differential heating of land and sea surface area by solar radiation. Also, see here for land and sea breezes.Water has a greater heat capacity when compared to land, this means that land absorbs and emits radiation more efficiently and faster.Since solar radiation penetrates several meters of a body of water, it warms the water very slowly. However, only the upper surface of the land which is few centimetres are heated, and warming occurs as quickly as possible as the result of the solar heating. Most especially during clear summer days, the surface of the land gets heated quickly, making the surrounding air near the surface to become warm and at the same time decreasing its density. As a result, the air begins rising over the land, lowering the atmospheric pressure near the surface relative to the pressure at the same altitude over the water surface. The rising air increases the pressure over the land relative to that above the water at altitudes of approximately 100200 m. The rising air over the land surface is replaced by cooler air from over the water surface. This air is also replaced by subsiding air from somewhat higher layers of the atmosphere over the water. Air from the higher-pressure zone several hundred meters above the surface then flows from over the land surface out over the water, completing a circular or cellular flow. This phenomenon usually takes place as a result of the presence of high pressure in the sea during the day and low pressure in the land during the day. The sea breeze and land breeze are more localized than prevailing winds, hence they are referred to as local winds. Because land absorbs solar radiation far more quickly than water, a sea breeze is a common wind along with the coastal environment. However, a prevailing wind plays an important role in determining the shape and shore relative location of the sea breeze. The prevailing wind determines whether or not a sea breeze will be detectable on land (a very strong offshore prevailing wind will obstruct the sea breeze from approaching the coast, and at the same time exerts an influence on its behavior.

The sea breeze and land breeze occur where there are large water bodies or coastal areas, Sea breeze takes place during the day, during this time, the land is warmer than the water while the land breeze takes place during the night. Wind usually blows from areas of high pressure to areas of low pressure. The result of the wind affects land and sea, hence, leading to the sea breeze and land breeze.

The land breeze and sea breeze system are very shallow with an average depth of 1-2 km. Over the lakes, the height of circulation is much less. In warm tropical areas, where there is intense solar heating throughout the year, stronger and regular breezes occur more compared to higher latitudes.

Sea breeze front

The temperatures of the coastal areas on a regular basis are determined by sea breezes. If an offshore flow exists when a sea breeze forms, then there will be a region where the two opposing surface winds meet and are forced to ascend; this region is called a sea breeze front. In other words, a sea-breeze front is a weather front formed as a result of a sea breeze, it is also known as a convergence zone. This happens when the cold air from the sea meets the warmer air from the land and creates a boundary like a shallow cold front, if there is enough moisture in the atmosphere, this front can produce cumulus clouds and precipitation, and if the air is unstable, the front can sometimes trigger thunderstorms. The intensity of the sea breeze fronts varies especially alongshore direction, even along nearly homogeneous coasts.

Sea breezes typically impact the land within some tens of kilometres of the coastline. They consistently occur in coastal areas throughout the world and are responsible for the changes in a coastal climate, hence coastal climate may become several degrees cooler in summer than the nearby inland areas and may experience higher levels of precipitation too. Even though sea breezes affect all coastal locations to a large extent, there are locations where the effect is larger, often because of the geometry of the coastline. For instance, Islands or a relatively thin peninsula of Florida can cause sea breezes from opposing sides that will converge and greatly influence the occurrence of precipitation. Peninsula winds blow easterly (from the east) from the Atlantic Ocean and westerly (from the west) from the Gulf of Mexico. This makes the sea breezes to converge towards the central part of the peninsula.The air moves upward and forms clouds, precipitation, and triggers thunderstorms. However, the local climates of Florida and the East Coast are greatly influenced by the sea breezes. Sometimes, when the sea breezes are not so powerful and do not converge on the inland over Florida, forest fires can be triggered especially when there is no relief from precipitation and the proper conditions exist due to the sea breezes. Sea and land breezes that occur in association with larger lakes are called the lake and land breeze

Effects of sea breeze

  • Sea breeze brings relief from oppressive hot weather
  • It can trigger thunderstorms especially when the air carries moisture and it unstable.
  • It brings changes to local air quality
  • It allows moisture in the air