GEOL110_Natural Hazards CH 9
GEOL110_Natural Hazards CH 9 GEOL 110
Long Beach State
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This 6 page Class Notes was uploaded by Doris M on Sunday April 24, 2016. The Class Notes belongs to GEOL 110 at California State University Long Beach taught by Ewa Burchard in Spring 2016. Since its upload, it has received 4 views. For similar materials see Natural Disasters in Geology at California State University Long Beach.
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Date Created: 04/24/16
Natural Hazards Objectives Have you experienced severe weather conditions, if so what type? How would you describe the severe weather-what parameters would you identify? What was the geographic location (altitude, latitude, continent, country)? What was the topography distance from a body of water (ocean, lake) 1.what are 3 ways of heat transfer in the atmosphere? 2.How earths energy balance/exchange produces climate weather? 3.what are layers of Earths atmosphere and their properties? 4.what are severe weathers? 5.What are air masses role in distribution of hazardous weathers? 6.How severe weathers impact people? 7.How atmospheric hazards impact other natural hazards? 8.What are natural service functions of severe weather? 9.How can we minimize the effects of severe weather hazards? 1999 and 2013 Tornadoes of Moore, Oklahoma -ex. Of power and human response -1999 tornado outbreak (great plains) May 3rd -highest-ever recorded wind speed of 484 km/hr in avg 100km/hr -destruction on 61 km x 1.6 km path in ~90 min -killed 36, injured 295, and damaged/destroyed ~10,000 homes -2013 tornado of comparable destructiveness (EFS) -similar EFS event/path, 39 min, path 27km x 2 km, 322 km/hr winds -1200 homes destroyed -Doppler radar serves to detect tornadoes (watch and warning system) -EF scale defined based on wind speed (enhanced Fujita Scale 1-5) -btwn Rockies/Appalachian mountains - Great Plains (tornado Alley) -usually tornadoes form during Spring and summer (lake afternoon-evening) -caused by the warm air -the surface of the air becomes warm enough for water to be evaporated -US -1000 tornados/yr 40% in Tornado Alley -because so many tornadoes happen within the alley, Oklahoma was defined as a storm ready city -problem in area-Oklahoma expands during raining conditions and can effect construction -difficult to construct underground shelters - -Enhanced Fujita Scale: measures magnitude of the wind Energy -fundamental to understanding severe weather -Force -push or a pull -magnitude measured y how much a body is accelerated -measured in Newtons (N) -F=ma -Work -done when energy is expended -physics: force applied to an object and it moved a certain distance in the direction of the applied force -measured in Joules (J) -W=Fs -Power -rate at which work is done -measured in Watts (W) -P=E/t -concerned with large amounts of energy in atmospheric processes -measured in exajoules (EJ) 10^18 to describe global energy Types of Energy -must expend energy to do work -potential energy -stored energy -ex. Water held behind a dam -kinetic energy -energy of motion -ex water flowing fro the dam -Heat Energy -energy of random motion of atoms and molecules -sensible heat: heat sensed or measured by thermometer -latent heat: amount of heat absorbed or released when a substance changes phase. Exchanged heat Heat Transfer -Conduction -transfer thru atomic or molecular interactions -2 bodies in contact with one another -convection -transfer thru mass movement of a fluid -hot air rises displaces cool air which falls -creates a convection cell -Radiation -transfer thru electromagnetic waves -emitted by any substance that possesses heat Earth's Energy Balance -A general equilibrium btwn incoming and outgoing radiation -Earth intercepts only a fraction of the sun's radiation -Sun's energy drives hydrologic cycle, ocean waves and currents, and global atmospheric circulation -Nearly all of the energy available at Earth's surface comes from the sun Electromagnetic Energy -Most of the sun's energy is electromagnetic -described by the wavelength -distance from one crest to the next -All wavelengths are part of electromagnetic spectrum -only a small part of this is visible -the shorter the wave, the more energy it carries Energy Behavior -Once electromagnetic energy from the sun reaches Earth, it is -redirected -reflection back to space by clouds, water, land -scattering dispenses energy in many directions -transmitted -energy is passed thru atmosphere -absorbed -alters molecules… -Temperature depends on amount of energy absorbed or reflected -reflection depends on albedo -described the reflectivity of surfaces -dark woodlands reflect 5% to 15% -Light grasslands reflect 25% -Absorption -Energy that is not reflected is absorbed -different objects absorbed different wavelengths -hotter objects radiate energy more rapidly than shorter wavelengths -scattering ex.- when the sun sets, the colors from the electromagnetic spectrum is scattered. -Temperature depends on amount of energy absorbed or reflected -Reflection depends on albedo -the reflectivity of a surface -dark woodlands reflect 5% to 15% -light grasslands reflect 25% -Absorption -energy that is not reflected is absorbed different wavelengths Tornado Occurrence in the US (img) -Why do the number of tornadoes prevail in the Eastern US? -tornado alley? -why specifically there? -the different mountains in that area -air masses What happens to heat energy? -water evaporates from oceans -ocean is cooling -water vapor condenses to form clouds -water vapors cool down to form clouds -the release energy -water vapors turning into clouds -rain forms from clouds because -volume of droplet inc -droplets freeze, get heavier, fall and defers at lower altitude -cloud droplets attach to particulates and form larger volumes -cloud droplets freeze -droplets release heat -img: Energy exchange -melting: in freezing of water, 80 ca of energy is released -evaporation: in heating of water, 800 ca is absorbed The Atmosphere -thin gaseous envelope that surrounds Earth -gas molecules -suspended particles of solid and liquid -falling precipitation -Causes weather experienced every day -Responsible for trapping heat that keeps the Earth warm -Knowledge of structure and dynamics critical to understand severe weather Composition of the Atmosphere -composed mostly of nitrogen and oxygen -smaller amounts of argon, water vapor, and carbon dioxide -other trace elements and compounds -water vapor -important for cloud formation and circulation -comes from evaporation off of Earth's surface -Humidity describes amount of moisture in atmosphere at particular temp -relative humidity is the ratio of water present to the amount that saturates the air -inc at night because of cooler temps, decreases during the day due to heating -when water vapors are present the heat energy will be released Structure of the Atmosphere -water vapor content and temp vary from Earth's surface to its upper limits -Troposphere -where the weather takes place -where the air is stable -upper boundary is tropopause -temperature decreases with inc altitude -presence of clouds -very small water droplets or ice crystals that condensed from the atmosphere -cumulus: puffy fair weather clouds -cumulonimbus: tall, dark storm clouds -just barely in the troposphere -contains most of the atmospheric carbon dioxide and methane -altitude inc-temp inc -more density closer to the earth -when the volume dec, the temp decreases -if you have air and you keep pumping air into something, the temp inc -a source of heat Cloud Types Associated with Severe Weather -4 aspects of atmosphere directly related to severe weather -atmospheric pressure and circulation patterns -vertical stability of the atmosphere -Coriolis effect: the appearance around the Earth because of Earth's circulation -Interaction of different air masses -unstable air: the air is moving Tornadoes (video) -begin with a thunderstorm-Super cell thunderstorms -ex. Flashes of lightning, hail.. -rising air-when condensation occurs, condensation releases heat and produces updrafts of air -vortex can form forming a mesocyclone -if the funnel of air gets into the cloud base, it can turn into a tornado Atmospheric Pressure and Circulation -atmospheric pressure also called barometric pressure -weight of a column of air above a given point -force exerted by molecules on a surface -in the atmosphere, pressure decreases with inc altitude -changes in air temp and movement are responsible for horizontal changes in pressure -temp influences pressure cuz cold air is more dense and exerts greater pressure on surface -global variations in temp cause global winds -All equator air is warm and low in density -creates low pressure zones at the equator -air rises, condenses, forms clouds and rain -cooler, drier air sinks at latitudes around 30 degrees causing deserts -similar vertical circulation cells observed at middle and high latitudes -the air that is above the equator rises up and will contain vapors -moist air rises up warm and cools down then sinks -Jet Streams -mid latitude air masses of different temperatures colliding near tropopause -westerly winds due to Coriolis effect -greater the temp difference, faster the flow -Northern Hemisphere has 2 jet streams -polar jet stream -polar stronger > subtropical -boundary btwn cold arctic polar and warm subtropical/tropical masses -subtropical jet stream -weak during the summer -strongest in winter (temp gradient btwn air masses is greatest) -cold masses of air produce faster winds The Atmosphere -atmosphere: the thin gaseous envelope that surrounds Earth. Made of gas molecules suspended particles of solid and liquid, and falling precipitations -troposphere: lowest layer of the atmosphere, extends 8-16 km above surface -rapid upward decrease in temp that results from decreasing air pressure w/ inc altitude -relative humidity: the ratio of the water vapor present in the atmosphere to the max amount of water vapor that could be there for a given temp -warm air has he capacity to hold more water vapor that cold air