The Role of Solar Energy (continued) Page 181

This causes unequal heating of the Earth’s surface Water has a high specific heat- heats up and cools down much slower than land This causes unequal heating of the Earth’s surface

Unequal Heating of the Earth As the sun’s energy strikes the Earth, the Earth’s surface is heated unequally.

Unequal Heating of the Earth This occurs because land heats up and cools down faster than water.

Unequal Heating of the Earth If you have ever been to a pool in the summer, you have experienced this unequal heating. In the middle of the afternoon the concrete surrounding a pool feels very hot while the pool water feels cool. In the evening, however, the concrete will feel cool to your bare feet and the pool water will feel warm.

Unequal heating powers atmosphere and oceans. This unequal heating and cooling powers the motion of the atmosphere and the oceans.

Warm Air/Warm Water Rise When air and water are heated, their molecules move faster and farther apart. This reduces the density of the water and air causing their molecules to rise.

Cool Air/Cool Water Fall On the other hand, cooler air and water molecules move slower, are denser, and begin to descend or fall.

Convection In the atmosphere rising warm air and descending cooler air forms a cyclic, or circular, rising and falling pattern called convection.

Unequal Heating Causes Air To Move

Moving Air Is Called WIND

Convection in Air

Convection in Water This same circular motion caused by heated molecules occurs in water as warmer, less dense water rises and cooler, denser water falls.

Convection Moves Ocean Water Click for movie clip

Radiation and convection from the Earth’s surface transfer or distribute heat energy. This energy powers the global circulation of the atmosphere and the oceans.

Evaporation Leads to Clouds As oceans, lakes, and rivers absorb heat energy, water vapor is carried up into the atmosphere by rising warm air.

Evaporation Leads to Clouds Water vapor is formed from water that evaporates from the Earth’s surface.

Evaporation Leads to Clouds As the warm air rises, it actually gives off some heat as the water vapor in it cools down and changes into minute, or tiny, condensed water particles.

Evaporation Leads to Clouds As more and more of these condensed water particles join together, a cloud is formed. If the water particles become too large and heavy, they fall to the ground as precipitation.

Rapidly Moving Hot Air Can Cause… When heated air rises rapidly into the atmosphere, the result can be a storm. A storm is a violent weather condition caused by a disturbance in the Earth’s atmosphere.

Rapidly Moving Hot Air Can Cause… One kind of storm is a thunderstorm. Thunderstorms usually have strong winds, heavy rain, thunder, and lightning. Some thunderstorms are formed when the land is strongly heated. This results in a mass of cooler air forcing its way underneath rising warm air.

Rapidly Moving Hot Air Can Cause… Hurricanes are another type of storm that forms due to the rising and falling convection patterns. Hurricanes form over warm, tropical water. They begin as thunderstorms and grow larger as they take in more and more heat and moisture from the warm ocean water.

The Formation of a Hurricane

Hurricanes 101