Wind directions

[ejwb]

Main Question or Discussion Point

Why does the wind blow off the ocean during the day at the beach, and off the land during the night?

 

[ImAnEngineer]

I didn't know about that. I think it must have to do with pressure though. I guess pressure above the sea rises during the day because of evaporated water. Sounds logical to me, but don't take my word for it ;) .

 

[wavingerwin]

Why does the wind blow off the ocean during the day at the beach, and off the land during the night?

During the day, the sun heats up both land and sea.
Sea heats up more quickly than land. This makes the air above the sea hotter than air above the land. Hence, air pressure at above sea is higher (pressure is directly proportional to temperature.) Air flows from higher to lower pressure, hence wind blows from land to sea.

During the night both sea and land cools down.
Sea cools down more quickly than land, making it colder than the land at night.
So, pressure is higher for air above the land because of higher temperature, and hence wind blows from land to sea.

The basic concept is that sea changes temperature more easily than the land.

 

[rcgldr]

Depends if you're on west coast or east coast. The main affect is sun heating the air over sea or land based on the sun's position. On the east coast you get an ocean breeze and higher humidity during the day, and a dryer land breeze during the night. On the west coast, it's the opposite. This assumes prevailing winds aren't dominant.

 

[russ_watters]

During the day, the sun heats up both land and sea.
Sea heats up more quickly than land. This makes the air above the sea hotter than air above the land. Hence, air pressure at above sea is higher (pressure is directly proportional to temperature.) Air flows from higher to lower pressure, hence wind blows from land to sea.

During the night both sea and land cools down.
Sea cools down more quickly than land, making it colder than the land at night.
So, pressure is higher for air above the land because of higher temperature, and hence wind blows from land to sea.

The basic concept is that sea changes temperature more easily than the land.

Yikes, no! Pretty much every bit of that is wrong!

First, the land heats up faster than the sea becaue you only heat up the very surface of the land. With the sea, convection currents make it tougher to heat the very surface (there is mixing). So the air above the land gets warmer. Warmer air is less dense than colder air, so the warm air above the land rises and pulls the colder air from above the sea in to replace it.

At night, this is reversed - the land also cools faster than the sea.

 

[wavingerwin]

Yikes, no! Pretty much every bit of that is wrong!

Gah! my bad..:shy: