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Chapter 19 Do Now: Atmosphere - a mixture of gases that surrounds a planet, such as Earth abundant elements = nitrogen, oxygen, & argon abundant compounds = carbon dioxide (CO2), & water vapor (H2O) carries various kinds of tiny solid particles, like dust & pollen Makes up about 78% of Earth’s atmosphere Maintained through the Nitrogen Cycle 1. removed from air by nitrogen-fixing bacteria 2. bacteria change nitrogen into compounds plants use 3. decay releases nitrogen back into the atmosphere Makes up about 21% of atmosphere Animals, bacteria, & plants remove oxygen from the air Plants make oxygen during photosynthesis Water evaporates from oceans, lakes, streams, & soil It enters air as the invisible gas, water vapor It is removed by condensation & precipitation Amount of water vapor in the atmosphere depends on: time of day Location season Ozone (O3)- gas molecule made up of three oxygen atoms Forms the ozone layer absorbs harmful ultraviolet (UV) radiation from sun Without the ozone layer, living organisms would be severely damaged by the sun’s ultraviolet rays Human activities damage the ozone layer The atmosphere contains various tiny solid & liquid particles, called particulates. Particulates can be: volcanic dust, ash, microscopic organisms pollen & particles from meteors Heavy particles don’t remain in the atmosphere for long, but tiny particles can remain suspended in the atmosphere for months or years. Gravity holds the gases of the atmosphere near Earth’s surface. Atmospheric pressure - force per unit area that is exerted on a surface by the weight of the atmosphere Atmospheric pressure is exerted equally in all directions—up, down, & sideways. Atmospheric pressure changes with: Temperature Altitude Water Vapor As temperature atmospheric pressure As altitude atmospheric pressure Meteorologists use three units for atmospheric pressure: atmospheres (atm) millimeters or inches of mercury millibars (mb) The average atmospheric pressure at sea level is 1 atm. Meteorologists measure atmospheric pressure by using an instrument called a barometer. One type of barometer is the mercurial barometer. Pressure presses on the liquid mercury Height of the mercury changes The greater the atmospheric pressure is, the higher the mercury rises 1. The Troposphere lowest layer part where weather conditions exist 2. The Stratosphere contains the ozone layer 3. The Mesosphere coldest layer of the atmosphere 4. The Thermosphere uppermost layer of the atmosphere includes the ionosphere & the phenomena known as auroras. Any substance in the atmosphere that is harmful to people, animals, plants, or property is called an air pollutant. The main source of air pollution is the burning of fossil fuels, such as coal & petroleum. Do Now: Radiation - includes all forms of energy that travel through space as waves. travels at a very high speed — 300,000 km/s. types of radiation differ in the length of their waves Electromagnetic spectrum - all of the frequencies or wavelengths of electromagnetic radiation Clouds, dust, & water disrupt the paths of radiation from the sun & causes scattering. Scattering - occurs when particles & gas molecules in the atmosphere reflect & bend solar rays. causes rays to travel out in all directions without changing their wavelength Albedo - fraction of solar radiation that is reflected off the surface of an object Depends on color, texture, composition, volume, mass, transparency, state of matter, & specific heat of the material. Solar radiation that is not reflected is absorbed by rocks, soil, & water. It heats the surface. Sometimes, warm air bends light rays to produce an effect called a mirage. Greenhouse effect - warming of the surface & lower atmosphere of Earth that occurs when carbon dioxide, & water vapor absorb & reradiate radiation The amount of solar E that enters Earth usually equals the amount that escapes into space. However, human activities, in addition to natural causes, are changing the balance causing temperature to increase Increases in carbon dioxide may intensify the greenhouse effect & may cause Earth to become warmer. Radiation from the sun does not heat Earth equally at all places at all times. Temperature of the atmosphere depends on: Latitude Surface features Time of year & day Latitude is the primary factor that affects the amount of solar energy on Earth. Because Earth is a sphere, the sun’s rays do not strike all areas at the same angle. Temperature varies seasonally because of the tilt of Earth’s axis. The molecules in a substance move faster as they become heated. collide & transfer energy, which warms the new substance. Conduction - transfer of energy as heat from one substance to another by direct contact. Convection – process by which air or other matter rises or sinks b/c of differences in temperature. Heats Earth’s atmosphere Causes winds Conduction Convection Do Now: The circulation of the atmosphere & oceans is affected by Earth’s rotation. Coriolis effect - curving of the path of a moving object from an otherwise straight path due to Earth’s rotation Deflects a moving object along a path Depends on speed, latitude, & direction of the object Northern hemisphere = to right Southern hemisphere = left Air that flows from the poles to the equator does NOT flow in a straight line. Each hemisphere contains three looping patterns of flow called convection cells. Each correlates to an area of Earth’s surface, called a wind belt, that is characterized by winds that flow in one direction. These winds are called prevailing winds. Trade winds, westerlies, polar easterlies Trade wind - prevailing winds that blow from east to west from 30º latitude to the equator in both hemispheres named according to the direction from which they flow Northern Hemisphere trade winds = northeast trade winds Southern Hemisphere = southeast trade winds Westerlies - prevailing winds that blow from west to east between 30º and 60º latitude in both hemispheres Polar easterlies - prevailing winds that blow from east to west between 60 and 90 latitude in both hemispheres Where the polar easterlies meet warm air from the westerlies, a stormy region known as a front forms. Local winds are not part of the global wind belts. Breezes - blow at speeds of less than 50 Sea Breeze - cool wind moving from water to land Land breeze - flows from cool land towards the water Valley breeze - warm air from the valleys moves upslope Mountain breeze - cool air descends from the mountain peaks.