You have learned previously about convection. Convection also causes many different types of weather phenomena. You will learn about some of these phenomena in this activity.   

You have learned that warm air rises and cool air sinks and that this type of heat transfer is called convection. The winds you feel when you are outside all start with convection currents. This is how they work.

Land and sea breezes are convection currents of air that occur near a shoreline. These kind of currents are both created by differences in temperature near the surface of Earth.

On a sunny day, radiant heat from the sun strikes Earth’s surface. Heat is absorbed by land and water. But land and water heat at different rates. Land heats quickly but also cools quickly. Water heats slowly and takes longer to cool.

The first image below shows a sea breeze. The sun's rays warm land more rapidly than they warm water. Warm air is less dense so warm air rises. Air over the water is cooler. Cool air is more dense and sinks. Then the cool air flows toward land to replace the warm air that has risen.

On a hot summer day, if you are near the ocean or a lake and close to shore, you may feel a breeze blowing from the water to the land. This breeze is a sea breeze. It is a cool wind that blows from the water toward land. On a hot day, it is a cool and welcome relief!

The image above shows a land breeze. The sea loses heat more slowly than the land. The air over the sea is warmer. Warm air over the sea rises. Air over land is cooler. Cool air is more dense and sinks. Cool air flows toward the sea to replace the warm air that has risen.

A land breeze usually occurs in the evening. In the evening, the land cools down much quicker than do the waters of the ocean. As the land becomes cooler, so does the air above it. This results in air becoming more dense, forming a high pressure, causing winds to blow outward towards the sea. This is known as a land breeze.

 Land breezes often carry air pollutants out to sea, away from the cities near the coast. Land breezes are weaker than sea breezes because there is less temperature difference between the land and sea during the evening.