ATMOSPHERE The atmosphere has 5 layers. The Troposphere is the layer nearest the Earth’s surface. Electrically charged particles are found primarily in the ionosphere The exosphere merges into outer space and is farthest from Earth’s surface. Temperatures in the thermosphere are very warm. The stratosphere contains the ozone layer.

THE ATMOSPHERE, Continued Oxygen makes up 21% of the atmosphere. Nitrogen is the most common gas in air. Ozone is usually found in the upper stratosphere. Smog is formed when pollutants mix with oxygen in the presence of sunlight. Water vapor makes up 0-4% of the air in the atmosphere. Water is the only substance that exists as a solid, liquid, and gas in Earth’s atmosphere. This Photo by Unknown Author is licensed under CC BY-SA

HEATING The transfer of energy through contact is conduction, and is how energy is transferred from land and water to air. Convection is the transfer of heat which causes differences in air density (cold sinks, heat rises); it is caused by the flow of a heated material like water or air. Radiation is the transfer of energy through space by electromagnetic waves. Radiation is also how energy is transferred from the Sun to Earth’s surface.

Heating of the Earth Air in the troposphere (where we live) is warmed by heat from Earth’s surface. Air above the equator is heated more than at any other place on Earth. Wind patterns on Earth’s surface are created by differences in heating and the Coriolis effect (which is caused by Earth’s rotation). Reflection and absorption by the atmosphere prevents some radiation from reaching earth’s surface.

WIND The Doldrums are windless zones near the equator, where heat rises. Prevailing Westerlies are responsible for the movement of much of the weather across the USA. Steady winds between the Equator and 30 degrees latitude north and south are known as the trade winds. Air currents that blow near the poles (north and south) are the polar easterlies. Sea and land breezes happen because the land heats and cools more quickly than water.

Other Atmosphere Facts In the water cycle, water evaporates from the surface of the Earth (lakes, rivers, oceans, etc.) and condenses into clouds, then falls as precipitation. Chlorofluorcarbons destroy the ozone layer by destroying ozone molecules. The ozone layer protects us from ultraviolet radiation. Too much exposure to ultraviolet radiation can cause skin cancer.