Essential question: What causes the weather? 4 Elements of Weather Essential question: What causes the weather?

Weather Weather is the condition of the air around us at a specific place and time.

WHAT is Weather Wind Humidity Air Pressure Temperature

Wind Wind is simply air in motion. It is caused by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of very different types of land and water, it absorbs the sun’s heat at different rates. Cooler air rushes under warmer air and creates wind.

Wind

Measuring Wind Wind speed is measured with an anemometer. Wind direction is measured by a weather vane or wind vane. The arrow points to the direction the wind is coming from. Wind speed uses the Beaufort Wind Scale.

Wind

Humidity Humidity is the amount of water vapor in the air. Warm and hot air can hold more water vapor. Cold air does not hold as much water vapor. Measured by a hygrometer.

Air Pressure Air pressure is the force of air pushing on an area. As you go higher in the air, there is less air pushing down.

Air Pressure As air is heated, the molecules in the air move faster and further apart. As air cools, the molecules move slower and are closer together.

Cold Air and Warm Air Cold air has higher pressure than warm air because the molecules are closer together or more dense. Because cold air is more dense than warm air, it sinks, while warm/hot air rises.

Measuring Air Pressure Air pressure is measured with a barometer.

Air Pressure Differences in air pressure are shown on a weather map with circular lines called isobars. High pressure areas generally have dry, good weather. Low pressure areas generally have wet weather.

Air Pressure Symbols L = Lousy weather A blue H is the symbol for high pressure areas on a weather map. This means dry, good weather. H = Happy weather A red L is the symbol for low pressure areas on a weather map. This means wet weather. L = Lousy weather

Air temperature As the sun’s energy heats up Earth’s surface, the air particles move further apart. Earth absorbs heat energy during the day and loses heat energy at night. Measured with a thermometer.

Weather WHAT is Weather! The condition of the air around us. Wind Humidity Air Pressure Temperature The condition of the air around us.