Chapter 15 – The Atmosphere Atmosphere – A mixture of gases composed of 78% nitrogen and 21% oxygen. Gravity holds the gases close to the Earth making it thicker with higher pressure near the surface and thinner with lower pressure at higher altitudes. The Layers of the Atmosphere: Troposphere – the lowest, densest and closest layer to the surface of the Earth containing 90% of the mass of the atmosphere. Stratosphere – the gases in this layer are thin and do not mix. Thin with very little moisture. Mesosphere – the coldest layer characterized with a decrease of temperature with increasing altitude (inverse relationship). This is the middle layer but also is one of the highest layers. Thermosphere – one of the highest layers containing too few air molecules to successfully transfer any thermal energy. Temperatures may reach 1000°C. Ionosphere – composed of the upper mesosphere and lower thermosphere where nitrogen & oxygen atoms absorb harmful solar radiation. These gas particles become electrically charged (ionized) and form the auroras when energized by solar particles. This layer also reflects radio waves back to the surface.
Atmospheric Heating Energy from the sun reaches the Earth’s surface in the form of electromagnetic waves called radiation. Only about two billionths (2/1,000,000,000,000) of the sun’s energy ever reaches the Earth’s surface and half of that get absorbed by the water and land (50%). Thermal Conduction – The transfer thermal energy through a conductive material. Similar to cooking. Heat is transferred from the flame to the pot to the food. Convection – The transfer of heat by the molecules of a liquid or a gas. The movement created when warm air rises and cold air sinks.
Greenhouse Effect – The warming of the surface and lower atmosphere caused by water vapor, carbon dioxide, sulfur dioxide, nitric oxide (greenhouse gases) that absorb radiation and transfer the thermal energy to the surroundings. Global Warming – The unnatural, gradual average global temperature increase due to an increased concentration of greenhouse gases. Global & Local Winds: Wind – The movement of air caused by differences in air pressure. The greater the pressure differential, the stronger the wind. Differences in air pressure are caused by the unequal heating of the Earth’s surface with warm air rising at the Equator and cooler air sinking at the Poles. Convection (Hadley) Cells – Large, circular patterns that the air travels in, separated by high and low pressure belts located about every 30° latitude. Coriolis Effect – The curving of the Earth’s winds and ocean currents caused by the Earth’s rotation.
Global Winds: Polar Easterlies – Winds that blow from the poles to 60° latitude. Westerlies – The flow of air to the poles from the west to the east. This is the opposite of the Trade Winds and blow from 30° to 60° latitude. Trade Winds – Winds that blow from 30° south latitude to 30° south latitude. Named by sailor who traveled from Europe to the Americas. Doldrums – Located at the Equator where the Trade Winds meet and rise creating a very calm center of low pressure. Horse Latitudes – A region located at 30° latitude where the air sinks creating a high pressure, windless area. Many of the world’s deserts are located here. Jet Stream – A narrow band of high altitude, high speed winds that blow up to 400 km./hr. (240 m.p.h.) in the upper troposphere and lower stratosphere.
Local Winds – Winds that move air short distances and can blow from any direction. Can be created by a shoreline, mountain range or even a forest fire. Mountain and Valley breezes – Caused by differences in temperature created by changes in elevation. Valley breeze by day, mountain breeze by night. Breezes and winds are named by where they blow from. Air Pollution – The contamination of the air by pollutants from human and natural sources. Can cause coughing, headaches and lung cancers. Primary Pollutants – put directly from their source directly into the air. Car exhaust is the #1 human primary pollutant. Secondary Pollutants – A primary pollutant that reacts with other pollutants to create a new pollutant such as ozone and smog. Indoor air pollution is the result of the use of cleaners, heaters, dirty ductwork, chemicals from carpet, etc. Can be reduced with a proper ventilation system that mixes household air with outdoor air.
Acid Precipitation – precipitation that contains acids from air pollution. Acidification – Acid precipitation changing the acidity of the water and soil causing harmful effects. Acid Shock – A rapid change of the acidity of a body of water killing fish and damaging eggs of fish and amphibians. Most harmful in our area with the spring thaw. Ozone Hole – Harmful effects of chemicals called CFC’s (chlorofluorocarbons) that are breaking down the ozone (O3) into oxygen (O2) allowing harmful ultraviolet (UV) radiation to reach the Earth’s surface. Cleaning Up Air Pollution: Allowance Trading System – Limits the amount of pollutants that a company can release. Hybrid Cars – Uses both gasoline & electric power. Scrubbers – Devices that remove some pollutants before they are released into the air. Usually mounted on the tops of smokestacks. Cleaner fuels, catalytic converters, more efficient auto engines, etc.