Land and Ocean Breezes
Name: Cheryl C.
Why is it that wind blows in land off in the ocean during
When the sun heats the surface of the earth, the land heats faster than the
water. The warm land heats the air above it and that warm air becomes less
dense. It rises just as a hot air balloon. When the warm air rises it
draws air in to replace it. Along shorelines the replacement air comes off
the water creating what we call sea breezes. Interestingly, at night the
reverse happens because the land cools faster and we develop land breezes.
The land breezes, and sea breezes are due to pressure differences between
the land an ocean. These pressure differences are caused by temperature
differences over those areas. The air near the surface is heated by whatever
surface is beneath it. Land heats up quicker during the day compared to the
ocean, where the surface temperature changes very little from day to night.
As the air heats up in the day, the atmospheric pressure drops, because warm
air is less dense than cool air. When the pressure is lower over the land
relative to the ocean, the air over the ocean moves towards the lower
pressure. This produces what is called the "sea breeze." The sea breeze
can extend several miles inland from the ocean. This phenomenon also occurs
around the Great Lakes under certain conditions.
At night, the reverse occurs. The land cools faster than the ocean, and the
air over the ocean is warm, relative to that over land. Then the breeze
blows from the land towards the ocean.
Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO.
Click here to return to the Weather Archives
Update: June 2012