What is weather? • Weather is all the conditions of Earth’s atmosphere at one time and place. • The atmosphere is the layer of gases that surrounds Earth. • Four factors make up the weather in a place: • Temperature • Precipitation • Air pressure • Wind (contd.)
In some places, the temperature stays almost the same. In other places, it can change quickly. • Precipitation is water that falls from clouds. Rain, snow, sleet, and hail are all kinds of precipitation. 1. IdentifyGive an example of precipitation you have seen at your home. (contd.)
Air is made up of tiny particles. These particles have mass and weight. When they press against another object, they cause air pressure. • The more air there is above you, the greater the air pressure. The higher you go, the less air pressure there is. Air pressure is sometimes measured in inches of mercury. This diagram shows how air pressure drops as you go higher. (contd.)
Air that moves across Earth’s surface is called wind. Differences in air pressure and temperature cause air to move. • Hot air causes less pressure than cooler air. Lower-pressure air rises. Higher-pressure air flows in under it. 2. Relate Cause and EffectExplain how air pressure and wind are related.
What is climate? • Climate is the average of weather conditions in a place over a long time. Climate changes much less than weather. • Latitude affects climate. Places near the equator are usually warmer than places far from the equator. This happens because the energy from the sun is more direct near the equator. Near the equator, energy from the sun strikes Earth most directly. Near the poles, the same amount of energy spreads out over a larger area. (contd.)
Landforms affect climate. Mountains are usually cooler than the areas around them. • Mountains can affect the amount of precipitation an area receives. (contd.)
Oceans affect climate. Water heats up and cools down more slowly than land. The temperature of the air near an ocean does not change as much as the air farther inland. • Ocean currents affect climate. Warm currents make the air and climate near a place warmer. Cold currents make the air and climate colder. 3. DifferentiateExplain how knowing today’s weather forecast for your town is different from knowing its climate.