Chapter 6, Unit B Lesson 2 How do water and air affect weather?

Water is Recycled! Water Cycle-Never-ending movement of water from Earth’s surface to its atmosphere and back again.

Water Cycle Sun’s energy powers water cycle Evaporation-process of changing liquid water to water vapor. – Higher temperature – Faster water changes to water vapor Condensation-process of water vapor becoming liquid water Precipitation-any form of water that falls to the Earth

The atmosphere Blanket of air that surrounds earth. – Matter that takes up space and has mass. – 4/5 nitrogen – Almost 1/5 oxygen – Some carbon dioxide – Closest to the earth Water vapor – More vapor over oceans – Less vapor over deserts.

Air Pressure Gravity pulling air towards Earth’s surface. Air Pushes – Equal force in all directions Pressure – decreases the higher you go up – Changes with temperature

Air Pressure Low Pressure Warm air near earth’s surface Particles move apart Air pushes down w/less pressure Then rises High Pressure Cool air near earth’s surface Particles become more closely packed Denser, cooler air sinks

Wind Air moving from high pressure to low pressure