Atmospheric Properties The thin envelope of air that surrounds our planet is a mixture of gases, each with its own physical properties. The mixture is far from evenly divided. Two elements, nitrogen and oxygen, make up 99% of the volume of air. The other 1% is composed of "trace" gases Atmosphere of the Earth
Layers of the Atmosphere The atmosphere of the Earth may bedivided into several distinct layers, as the following figure indicates. Based on temperature, the atmosphere isdivided into four layers: the troposphere, stratosphere, mesosphere, and thermosphere. The earth's atmosphere is a very thinlayer wrapped around a very large planet. Energy is transferred between the earth's surface and the atmosphere via conduction, convection, and radiation. Ocean currents play a significant role in transferring this heat poleward. Major currents, such as the northward flowing Gulf Stream, transport tremendous amounts of heat poleward and contribute to the development of many types of weather phenomena.
Why is Atmosphere important? • It is these layers of gases which render the Earth habitable and provide protection from a continuous bombardment of electromagnetic radiation. The atmosphere is often used as a gaseous waste disposal area, with little sense of responsibility or understanding of the critical issues involved.
Sources of Air Pollution : • Point sources (Industries, Landfills) • Mobile sources (cars, aircraft, other transportation) • Area sources (mowers, Backyard BBQs) • Natural sources (volcanic activity) Ozone Source - chemical reaction of numerous pollutants; free radicals volatile organic carbons (VOCs) and nitrogen dioxide(s). Health Effects - breathing problems, reduced lung function, asthma, irritates eyes, stuffy nose, reduced resistance to colds and other infections. Environmental Effects - ozone can damage plants and trees; smog can cause reduced visibility
Atmospheric Processes The oceansplay an important role in exchanging and transporting heat and moisture in the atmosphere. Most of the water vapor in the atmosphere comes from the oceans. Most of the precipitation falling over land finds its way back to oceans. About two-thirds returns to the atmosphere via the water cycle. Practically all of the energy that reaches the earth comes from the sun. Intercepted first by the atmosphere, a small part is directly absorbed, particularly by certain gases such as ozone and water vapor. Some energy is also reflected back to space by clouds and the earth's surface.
The Ozone layer • Ozone is found in a thin layer of the Earth's atmosphere known as the stratosphere . • Mechanism of ozone layer destruction by CFCs Since CFCs are chemically stable, when released into the atmosphere they pass through the troposphere at about 20 km altitude without decomposing, reaching the stratosphere, where they are chemically decomposed by short-wavelength ultraviolet rays, releasing chlorine atoms. In a chain reaction, the chlorine atoms destroy the ozone layer in the stratosphere. • The physical and chemical structure of the atmosphere, the way that the gases interact with solar energy, and the physical and chemical interactions between the atmosphere, land, and oceans all combine to make the atmosphere an integral part of the global biosphere.
Global Warming The Earth's atmosphere, a thin blanket of gases, protects the planet from the harshest of the sun's ultraviolet radiation. The atmosphere, by trapping the Earth's warmth, keeps rivers and oceans from freezing. Carbon dioxide and water vapor are the most important gases in creating the insulating or "greenhouse effect" of the atmosphere.
Transferred energy via conduction, convection, andradiation. Conduction is the process by which heat energy is transmitted through neighboring molecules. Solids, such as metals, are good conductorswhile others, such as wood, air or water are poor ones, Conduction occurs right at the earth's surface. At night, the ground cools and the cold ground conducts heat away from the adjacent air. Convection transmits heat by transporting groups of molecules from place to place within a substance. Convection occurs in fluids such as water and air, which move freely. Radiation is the transfer of heat energy without the involvement of a physical substance in the transmission. Radiation can transmit heat through a vacuum. Energy travels from the sun to the earth by means of electromagnetic waves. The shorter the wavelength, the higher the energy associated with it.
Weather Forecasting Instruments Anemometer is used to measure wind speed and the direction that it is blowing. How we measure and record rainfall The gauge is sunk into the ground so that the top of the funnel is 30 cm above the ground and away from the shadow of surrounding trees and buildings.
Hydrologic cycles Water is essential for life on earth. It is recycled through the water or hydrologic cycle, which involves the following processes: Evaporation, the changing of water from a liquid to a gasCondensation, the changing of water from a gas to a liquidSublimation, the changing of water from a solid to a gasPrecipitation, the process by which water molecules condense to form drops heavy enough to fall to the earth's surfaceTranspiration, the process by which moisture is carried through plants from roots to leaves, where it changes to vapor and is released to the atmosphereSurface runoff, the flowing of water over the land from higher to lower groundInfiltration, the process of water filling the porous spaces of soilPercolation, groundwater moving in the saturated zone below the earth's surface