Atmosphere The Basics

Gas Composition Nitrogen (78%) Oxygen (21%) Other Gases - including carbon dioxide, argon, methane, water vapor (1%)

Atmospheric Dust Tiny, solid particles Mainly soil Includes salt, ash from fires, volcanic ash, particulate matter from combustion, skin, hair, bits of clothing, pollen, bacteria and viruses, and tiny, liquid droplets (aerosols)

Air Pressure The atmosphere is pulled to Earth by gravity More dense near Earth’s surface Less dense with elevation increase

Four Layers Based on temperature changes at different distances Troposphere Stratosphere Mesosphere Thermosphere

Energy Transfer Radiation: Transfer of energy across space/atmosphere Conduction: Heat from warm to cold when in direct physical contact Convection: Transfer of heat by air currents (hot air rises)

Heating the Atmosphere About half of the solar energy that enters the atmosphere passes through and reaches Earth’s surface Rest is absorbed or reflected in the atmosphere by clouds, gases, and dust, or reflected by the Earth’s surface

Energy Movement Air currents sink and rise as they cool and are heated, causing the air to move in a circular motion called a convection current

Greenhouse Effect Some heat is absorbed in Earth’s atmosphere by greenhouse gases, warming the air (water vapor, carbon dioxide, methane, and nitrous oxide) The amounts of greenhouse gases in Earth’s atmosphere vary