The wind will blow from the higher pressure over the water to lower pressure over the land causing the sea breeze.
The sea breeze strength will vary depending on the temperature difference between the land and the ocean.
At night, the roles reverse. The air over the ocean is now warmer than the air over the land. As the name clearly suggests these breezes occur along with coastal areas or along large lakes and water bodies.
A breeze is a cool and calm wind. These arise as a result of differential heating and cooling between land and adjacent sea areas during the day and at night.
The resultant pressure differences produce gentle breezes which affect coastal areas during calm clear anticyclonic conditions.
It is a breeze blowing toward the land from the sea, especially during the day owing to the relative warmth of the land.
The land heats up quickly by conduction and air rises.
The air moves towards the sea and falls since it is denser.
The air creates an area of high pressure over the sea while the land has low pressure since it is hotter when compared to the ocean’s surface.
The sea absorbs heat more slowly during the day and transmits it to greater depth so it remains cool.
A cool sea breeze moves from the sea towards the land.
The sea breeze is capable of reducing temperatures by as much as 15°C along with coastal areas and may produce fogs.
Effects of a Sea breeze:
- It lowers temperature on the land especially in the afternoons as cool air
from the sea replaces the rising warm air
- It is associated with onshore convectional rainfall which is normally
received in the early morning and afternoon hours
- It causes violent thunderstorms
- It results into high humidity over the land
- Thick cloud cover is formed over the land
- It leads to the formation of fog / misty conditions on the land which
results into poor visibility
On the other hand, is a coastal breeze blowing at night from land to sea, caused by the difference in the rate of cooling of their respective surfaces.
At night the reverse happens, Land quickly loses its heat while the ocean cools at a slower rate because water has a higher heat-specific capacity.
This means air over the water is less dense and begins to rise to create low pressure above the ocean’s surface. Cooler dense air from the land begins to move to the water surface to replace the warm rising air.
A cool gentle breeze blows towards the ocean. This is called a land breeze.
Causes of a Land breeze:
- Loss of radiation at the coastal lands at night. Land therefore cools faster than the sea/water hence temperatures are cooler over the land than the sea which retains much of its heat
- Water loses heat more slowly such that the air above it remains relatively warm
- Low pressure is created over the warm sea and high pressure over the cold land. Cool air from the land under high pressure blows towards the sea to replace the rising air hence forming a land breeze
Effects of a Land breeze:
- It results into lowering of temperature over the sea as cold air from the land blows towards the see
- formation of fog / misty conditions occurs over the sea as cold air from the land cools down the warm air over the sea leading to premature condensation as well as poor visibility
- Temperature inversion occurs over the sea as cold air from the land displaces warm air upwards over the sea
- Dense clouds and heavy offshore rainfall are experienced over the sea as warm air is displaced upwards to the condensation level
- It results into dry conditions on the land because little or no rainfall is received
- It results into violent thunderstorms
- It also causes high humidity over the sea / lake
The term “Chinook wind” is derived from the Indian word “Chinook” which means “Snow eater.”
It is called so because it is hot and it causes the melting of snow.
Chinook winds are experienced on the eastern slopes of the Rocky Mountains in the United States of America and Canada during the winter season.
Chinook winds are similar to Foehn winds in terms of development and effects. They only differ in areas of occurrence (operation)
Chinook winds are so hot that they can raise the temperature of an area by 19 degrees centigrade within 25 minutes.
It is a dry wind experienced on the leeward side of mountains when descending air becomes compressed with increased pressure.
It is experienced in the valleys of the northern Alps particularly in Switzerland during spring
Air is forced to move upwards the southern slopes of the Alps, where it later expands and cools.
Condensation takes place when the air is saturated. Rain and even snowfalls on the higher slopes.
On the leeward slopes, the air descends and gains heat due to an increase in temperature.
The air is compressed and warmed. Most of its moisture is lost and wind reaches the valley bottom as a dry hot wind known as a Foehn wind
The wind incidentally causes a sudden rise in temperature.
Being hot and dry, sometimes it triggers off wildfires in the Alpine valley as well as causing the low relative humidity