Natural Disasters Review Notes.docx

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Earth Sciences
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Sergei Basik

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Review Notes - Orographic effect o Air moving over continent may be forced to rise over mountain range, so expands and cools which is the orographic effect o Cooler air can hold less moisture, so precipitation occurs as air mass rises o Air moving down other side of mountain range is then warmer and drier o Rain shadow effect creates deserts on downwind side of mountain ranges o Ex. Warm, dry downslope Chinook winds in southern Alberta, Montana, Colorado and Wyoming - Coriolis Effect o Because the earth rotates from west to east, large masses of air and water on its surface tend to lag behind a bit o Oceans and air masses near equator move from east to west because they are fluid and not pulled at the same speed as solid Earth’s rotation o In northern hemisphere:  Water or air moving south will veer off to the west  Water or air moving north will veer off to the east o In the southern hemisphere the opposite is true o Forced curvature of path due to Earth’s rotation is Coriolis effect - Jet Stream o Over North America, jet stream marks the boundary between warm, moist subtropical air and cold, dry air to the north o Narrow 3-4km thick ribbon of high velocity winds blowing from west to east at altitudes near 12 km - El Nino o Oceanic circulation in equatorial Pacific usually is pushed westward by trade winds o Warm surfaces water off Peru is blown westward and replaced by upwelling of cold, deep, nutrient-rich water (productive fisheries) o Every six years (on average), Pacific Ocean circulation reverses in pattern called El Nini:  Subtropical trade winds weaken  Warm surface water remains in east Pacific  Incessant rain to west coasts of North and South America (coastal Peru, for example)  Fisheries suffer (no cold, nutrient-rich upwelling water) - Lake Effect Snow o Factors that determine the amount of snow  Expanse of ice-free water under storm track (for evaporation)  Duration of strong wind blowing over water (for greater evaporation)  Amount of moisture in atmosphere  Topographic rise downwind of water (to lift moisture and cause condensation) - Greenhouse Gases and Carbon Cycle o Carbon dioxide is vented into atmosphere by burning hydrocarbons o Mixes with water o Falls in rain o Dissolved in water, it may be precipitated as limestone or dissolved in the ocean o Taken in by plants ad stored in their tissues until they are wither buried and ultimately turned to peat/coal or burned in wildfires to again return to the atmosphere - Tornadoes: General Information o Narrow funnel of intense wind, usually with counterclockwise rotation (1% rotate clockwise) o Nature’s most violent storms, most significant natural hazard in Midwestern U.s. o Number of tornadoes is greatest in Tornado Alley: parts of Texas, Oklahoma, Arkansas, Missouri, Kansas - Tornado Development o Derive energy from latent heat released when water vapour condenses o Latent heat creates instability in the atmosphere o Generally form when there is shear in wind directions  Surface winds from southeast  Winds from west higher in atmosphere o Shear creates roll of horizontal currents o Roll can be dragged into vertical rotation axis by updraft in thunderstorm to form rotation cell o Cell sags to form wall cloud – most obvious danger sign for imminent formation of tornado o Smaller funnel clouds form within wall cloud, descend to ground to become tornadoes o Mammatus clouds are a second warning sign o Supercells can produce tornadoes - Classification of Tornadoes o Fijita scale was devised to classify the severity of tornadoes based on internal wind speeds and damage produced  F0 causes minimal damage  F5 blows away strong frame homes  F-scale damage chart and photographs correspond to wind speeds - Tornado Variations and Tornado-like Phenomena o Multiple vortex tornado  Is a tornado that contains several vortices rotating
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