Weather

The absorption of solar energy by the earth's surface and its atmosphere is directly responsible for most of the major factors making up weather patterns. For example, when the water in oceans, lakes, rivers, streams, and other bodies of water is warmed, it tends to evaporate and move upward into the atmosphere. The amount of moisture found in the air at any one time and place is called the humidity. Humans are very sensitive to this characteristic of weather.

Water that has evaporated from the earth's surface (or escaped from plants through the process of transpiration) rises to an altitude in the atmosphere at which the air around it is cold enough to cause condensation. When moisture condenses into tiny water droplets or tiny ice crystals, clouds are formed.

Clouds are an important factor in the development of weather patterns. They tend to reflect sunlight back into space. Thus, an accumulation of cloud cover may contribute to a decrease in heat retained in the atmosphere.

Clouds are also the breeding grounds for various types of precipitation. As water droplets or ice crystals collide with each other, they coalesce, and form larger particles. Eventually, the particles become large enough and heavy enough to overcome upward drafts in the air and fall to the earth as precipitation. The form of precipitation that occurs (rain, snow, sleet, hail, etc.) depends on the atmospheric conditions through which the water or ice falls.