Chapter 3: Earth's Modern Atmosphere
Chapter 3: Earth's Modern Atmosphere Geog 1112
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This 6 page Class Notes was uploaded by Alexandra Reshetova on Sunday January 24, 2016. The Class Notes belongs to Geog 1112 at Georgia State University taught by Aneela Qureshi (P) in Spring 2016. Since its upload, it has received 177 views. For similar materials see INTRO TO WEATHER & CLIMATE in Geography at Georgia State University.
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Date Created: 01/24/16
Chapter 3: Earth’s Modern Atmosphere Atmospheric Composition, Temperature, and Function Air = simple mixture of gases; naturally colorless, odorless, tasteless, and formless, blended that it behaves as if it were a single gas Top of our atmosphere = around 480 km above Earth’s surface Exosphere = (outer space); the rarefied, less dense atmosphere is near a vacuum; has scarce lightweight hydrogen and helium atoms weakly bound by gravity as far as 32,000 km Atmospheric Profile Earth’s modern atmosphere = thin envelope of faulty spheres or shells that pass into one another Three atmospheric criteria that scientists use to define layers of the atmosphere = temperature, composition, function Air pressure is created through air molecules Air pressure exists inside of us Earth’s atmosphere contains weight Gravity compresses air Atmosphere = exerts 1kg/cm^2 at sea level and 1013.2 mb (millibar) Atmospheric Composition Criterion Atmosphere = divides into two regions Two regions = heterosphere and homosphere Heterosphere The outer atmosphere (in terms of composition) Starts at about 80 km altitude and extends outward Less than .001% of atmosphere’s mass is here Gases here are not evenly mixed Gases = take place in layers sorted by gravity (according to their atomic weight) Lightest elements = at the margins of edge of outer space Heaviest elements = in the lower heterosphere Homosphere Below heterosphere Extends from 80km to Earth’s surface Blend of gases = uniform throughout; exceptions: concentration of ozone and variations of water vapor, pollutants, and trace chemicals Air sampling = happens at Mauna Loa Observatory Air in homosphere = nitrogen Nitrogen = integrates with humans through compounds food, not the air Oxygen = by-product of photosynthesis; makes up 1/5 of the atmosphere; makes compounds that compose about half of the crust Argon = less than 1% of homosphere; inert and not usable; mined or extracted from the atmosphere for uses on Earth Particulates = solids and liquid droplets that come in to the air from human and natural sources; another name: aerosols; they affect human health and energy balance Carbon Dioxide A natural by product of life processes; a variable gas-increasing Percentage in atmosphere = small Has increased since the last 200 years because of human activities (deforestation and burning of fossil fuels) The increase is rising Atmosphere Temperature Criterion Four zones = thermosphere, mesosphere, stratosphere, troposphere Thermosphere Known as heat sphere Corresponds to heterosphere The upper limit = thermopause Periods of a less active sun = may lower in altitude Periods of a more active sun = rises in altitude Temperatures rise sharply here The solar radiation here excites molecules to high levels of vibration Kinetic Energy = energy of motion; the energy that we measure as temperature Heat = made when kinetic energy is transferred between molecules; dependent on the density or mass of a substance To humans = the thermosphere would feel cold The higher number of molecules transfer their kinetic energy as sensible heat Mesosphere Area from 50 to 80 km above Earth; within homosphere Outer boundary = mesopause (coldest part of atmosphere) Can get meteoric or cosmic dust particles Noctilucent Clouds = can catch sunlight after sunset Stratosphere Extends from 18 to 50 km above Earth’s surface Temperatures rise here with altitude Outer boundary = stratopause Location of ozone layer Chlorofluorocarbons are increasing and ozone decreasing in the past 25 years Greenhouse Gases = on the rise; stratosphere cooling = response Troposphere The final layer Encountered by incoming solar radiation Supports = biosphere, life Region of weather activity 90% of total mass of the atmosphere is here 90% of all the water vapor, clouds, air pollution Tropopause = troposphere’s upper limit; altitude changes with season, surface temperature, and latitude Normal Lapse Rate = 6.4 Celsius km (average) Environmental Lapse Rate = the actual lapse rate may change because of local weather conditions Atmosphere Function Criterion Atmosphere = two zones (ionosphere and ozonosphere) Ionosphere and Ozonosphere = remove most of the harmful wavelengths of incoming charged particles and solar radiation Ionosphere Outer functional layer Extends throughout the thermosphere and into mesosphere Absorbs X-rays, cosmic rays, gamma rays, shorter wavelengths of ultraviolet radiation Auroral lights occur here Distinct regions = D, E, F1, F2 (broadcast communications, GPS Signals) D, E, F1, F2 = reflect radio wavelengths (includes AM radio and other radio broadcasts) (night time as well) GPS Signals = before reaching ground, have to pass through ionosphere Gases bend in the ionosphere The ionosphere weakens radio waves Ozonosphere Portion of the stratosphere that has an increased level of ozone Also known as ozone layer Ozone = highly reactive oxygen molecule made of 3 oxygen atoms Ozone = absorbs the shorter wavelengths of UV rays (all UVC; some UVB) UVA = long wavelengths; less intense than UVB; constant throughout the year (daylight hours); can penetrate clouds and glass UVB = intensity varies by time of day, season, latitude; cause of sunburn and skin reddening Ozone today = being depleted UV Index Helps Save Your Skin Weather reports include UV Index (UVI) UV Index = simple way of describing the daily danger of solar UV-radiation intensity (scale from 1 to 11+) A high number = great risk Zero = no risk (at night as well) Higher risk = UV damage to eyes and skin can happen over short period UV Radiation = varies according to: seasons, ozone depletion overhead, local weather conditions Pollutants in the Atmosphere Troposphere has: particles, other substances, natural and human caused gases They are known as : pollutants History of air pollution = Roman cities contained foul air from open sewers, fumes, smoke from fires Solutions to air quality = needs everyone’s ideas from around the globe Natural Sources of Air Pollution Air pollutants = carbon monoxide, nitrogen oxides, carbon dioxide, hydrocarbons Sources (most important) = forest fires, dust storms, volcanoes Other sources = pollen, other plants, weeds Aerosols = have the liquid droplets and suspended solids Dramatic natural source of air pollution = Mount Pinatubo eruption (1991) Wildfires = source of air pollution; has carbon monoxide, particulates, nitrogen oxides, volatile organic compounds Anthropogenic = human caused Anthropogenic Atmosphere = an unconfirmed label for Earth’s next atmosphere Anthropogenic Pollution Common in urbanized regions Human exposure to air pollution rises as urban populations increase Example: India Nitrogen Oxides, Ozone, Carbon monoxide, Volatile organic compounds, Sulfur Oxides, Peroxyacetyl Nitrates, Particulate matter = result from combustion of fossil fuels in transportation Vehicle Transportation = the largest source of air pollution (Canada and USA) Stationary pollution sources = give the most sulfur oxides and particulates Photochemical Smog Major component of anthropogenic air pollution Responsible for = reduced sunlight and hazy sky Photochemical Smog = comes from the interaction of sunlight and combustion products in car exhaust Volatile Organic Compounds (VOCs) = hydrocarbons that evaporate form gasoline Nitrogen Dioxide = high temperatures in automobile engines make this; is released from power plants as well Nitrogen Dioxide interactions = with water vapor to form nitric acid; with VOCs to produce peroxyacetyl nitrates; with oxygen and VOCs to form ground-level ozone Children = greater risk VOCs have chemicals such as indoor and outdoor pollutants Industrial Smog and Sulfur Oxides Coal replaced wood = over 300 years (not including some developing countries) Industrial Revolution = animate (animal sources like animal-powered farm equipment) energy to inanimate (nonliving sources like water, coal, steam) energy Industrial Smog = air pollution associated with coal-burning industries Smog: coined by a London physician in 1900 Industrial pollution contains high concentrations of carbon dioxide, sulfur oxides, particulates Sulfur Dioxide = reacts with oxygen to make sulfur trioxide; the main sources for sulfur dioxide are steel manufacturing and coal-burning electric utilities Sulfate Trioxide = highly reactive; in presence of water vapor or water makes small particles: sulfate aerosols Sulfuric Acid = forms in moderately polluted air at normal temperatures Sulfur Dioxide – laden air = corrodes metals, harmful to health, makes building materials worsen faster Particulates/Aerosols Particulate Matter (PM)= the diverse mixture of fine particles (liquid and solid) that pollute the air and affect human health; also referred to as aerosols Examples = dust, haze, smoke Black Carbon = soot; an aerosol; made in small villages mostly; an outdoor and indoor pollutant; made up of carbon (pure) absorbs heat in the atmosphere; changes the reflectivity of ice surfaces and snow Greatest health risk = PM2.5; 2.5 microns Organics = biological materials (pollens) Ultrafines = little particles at a size of PM0.1; cause of health problems Natural Factors That Affect Pollutants Regional and local landscape characteristics, winds, temperature inversions Winds Gather and move pollutants Dust is moved by wind and can come from natural sources Dust = can be tracked by chemical analysis Haze = a concentration of microscopic particles and air pollution that reduces air clarity Local and Regional Landscapes Hills and Mountains = barriers to air movement; can direct movement Example = places with volcanic landscapes (Hawaii and Iceland) Temperature Inversions Temperature Inversion = happens when the normal temperature reverses and starts to rise at some point Can occur at any elevation When an inversion happens = colder air lies below a warmer air layer Instead of being carried away: pollutants = trapped under inversion layer Inversions result from = topographic situations; certain weather conditions Benefits of the Clean Air Act Air pollutants = became smaller because of the Clean Air Act
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