At night, a reversed thermal circulation appears (the land breeze which usually is less intense). The sea breeze is usually weaker than the general synoptic winds but features a larger periodicity and a higher predictability. The sea breeze layer thickness ranges from 50 m (at dawn) to 300–400 m. The air over the land, that gained altitude, travels hundreds of kilometres offshore (up to 200-300 km), where subsidence occurs, closing the thermal cycle. The air over the land is heated faster, and gains altitude, while the air over the sea moves inland forming a narrow cold front. The sea breeze is a thermal circulation showing a diurnal cycle in the local scale in coastal areas. When the summer monsoon is culminating in July, winds will reach gale force and the waves can easily rise to 4-5m (significant wave height) in the Arabian Sea – this is rather annoying for the mariners sailing between Southeast Asia and the Red Sea. The transition phases between the two monsoon regimes is in April/May and October/November. The most known monsoon is the one in India and is normally defined as seasonal changes in precipitation and the atmospheric circulation (with seasonal reversing winds) associated with the asymmetric heating of land (Asia) and sea (Indian Ocean). The summer and winter monsoons are in fact large sea and land breezes that have an annual variation instead of a 24-hour variation. If you want to read more about visibility reducing phenomena you can read this article. It is not uncommon for a sunny spring morning in the coastal areas to turn into a cold, humid and grey foggy day in the afternoon due to the sea breeze – just ask the San Franciscans! In addition, the sea breeze can move mist and fog from sea to a coastal region – in Danish we call this “havgus”.įog over the sea is also a spring and early summer phenomenon because the cold sea can cool the air to the dew point where fog is formed.
#Land breeze how to
If you want to read about how to interpret a satellite image you can read this article. The centre of a prevailing high pressure that day were located near the island Bornholm and southernmost Sweden. Visually you can see the sea breeze in the way the cumulus clouds have formed over the central part of Zealand. Satellite image from 20th May 2018 displaying a sea breeze over the island Zealand and the southwestern part of Sweden. The two sea breezes can move slowly inland during the daytime and in special cases can meet over the Jutland Ridge.
East Jutland may have easterly winds, while West Jutland has westerly winds at the same time. Take for example the Danish peninsula Jutland. The sea breeze can be established along several coasts at the same time over islands and peninsulas - as long as the distance from coast to coast is less than 300-400km. This will cause a rising air flow and cumulus clouds can be formed. This wind is cold due to the cool sea surface temperature and as the cold air enters the warm land, the air is heated from below. But once the sun has warmed the air over land, the sea breeze will be established. These conditions are met by a high pressure in spring, which may have weak winds in the morning hours. The best conditions for the occurrence of sea breeze are cloudless weather, generally weak wind conditions and a cold sea. Illustration of the sea breeze and land breeze (Designed by brgfx / Freepik) Optimal conditions The difference in the air pressure therefore causes the air to move from the sea towards the coast – this wind is called a sea breeze. The sea breeze forms when the sun warms the land area so much that the surface air pressure drops.Īs the heating is not nearly as efficient over the cold sea, the air pressure does not change here. In the coastal areas, especially in the spring months, this can create a fresh onshore wind in the daytime and an offshore wind in the nighttime. It originates from the cold sea after the cooling winter and is due to the temperature difference between the warm spring air and the cold sea water.
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