GEOL110_Natural Hazards CH10.5
GEOL110_Natural Hazards CH10.5 GEOL 110
Long Beach State
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This 5 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 5 views. For similar materials see Natural Disasters in Geology at California State University Long Beach.
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Date Created: 04/24/16
Hurricanes and Extratropical Cyclones Hurricane Sandy -7 days form formation to landfall -south of NY -storm to largest Atlantic hurricane on record -"Superstorm Sandy" -great size, atypical path, merged with an arctic cold front -winds slowed upon landfall - storm not hurricane -2nd most expensive storm in US (after Katrina) -eye size- 2000 km -when a hurricane moves above the ocean, it becomes powered by the precipitation of the ocean -hurricane slows down when its over land -the hurricanes of such high level are considered superstorms -their names will not be reused because they were significant in magnitude -the eye of the storm moves slower than the surrounding winds -highest destruction where the winds are faster Intro to cyclone -Bermuda High- high pressure means the earth is sinking -sinking earth -not stationary, moves to the north or south -based on the Bermuda high there is a possibility it will hit the coast or not -lower pressure forms when there is evaporation in the ocean -depending on where the cyclones form they have different names -classified by intensity of winds -hurricanes -develop on the SE of Africa - known as cyclones -develop on the Atlantic -form where there is enough heat energy -from on the SE pacific -develop close to Australia known as typhoons -why do hurricanes develop in the certain locations? -the heat is required and the ocean depth needs to be heated -long term heating of the ocean -heat is required -the water circulation of the world moves cold water making it not warm enough for the hurricane -the warmer the ocean the more the hurricanes will develop -over warm tropical water 5 - 20 degrees of latitude -tropical depression -extratropical cyclones -form over land or water in temp regions -come from temp contrasts along fronts Classifying cyclones -Saffir Simpson scale: classifies cyclones -category 1-4 -category 1: 119-150 km /hr -1.5 meter of the surge -cat 2: wind speed inc to 150-170 km /hr -category 3: wind speed: 180- 200 km / hr -category 4: 200-250 km / hr Naming cyclones -female or male names -assigned in sequence -can be assigned and reassigned names -assigned by World Meteorological Organization Development -disturbance -wind speed inc -area affected is about 200-600 km -lasts more than 24 hrs -rotation developing due to Coriolis effect Tropical depression -wind inc and low pressure develops Tropical storm -higher wind speeds Tropical Cyclones -Hurricanes -vertical temp gradient: atmosphere must cool quickly with inc altitude -weak vertical wind shear: strong winds aloft prevent hurricane development -Hurricane Structure -rain bands: clouds that spiral inward around center -counterclockwise in Northern Hemisphere -inc intensity towards the center of the hurricane -eyewall: innermost band of clouds -contains the greatest winds and rainfall -hot towers can develop within the eyewall 6 hrs b4 a storm intensifies -eye: area of calm at center of the hurricane Stadium - like cloud form a hurricane's eye wall Hot Towers in Hurricane Katrina Development of an Extratropical Cyclone -warm air and cold air -the photo shows stationary fronts -when a cold and warm front meet they can create an upward wind -circulations start and causes cyclonic movement Structure of an Extratropical cycle -form on the eastern coast of the US, some on the west coast -less frequent in Hawaii and Atlantic coast -conveyor belt-fast moving winds tht affect the cyclone movements Regions at Risk for Hurricanes and Major Hurricane Hazard Map -lighter color indicate slower winds -slower winds at the coast -darker color indicates faster winds Geographic Regions at Risk for Cyclones -if the Bermuda height moves higher or lower the path of the hurricane can change Typical Tropical Cyclone Paths and Regions of Formation -we mostly see hurricanes on the NW pacific, East Pacific, Indian Ocean, S Atlantic, SE Pacific -no hurricanes on the other places because the water is probably not warm enough or there is no Coriolis effect Geographic Regions at Risk for Cyclones Cont. -there are lost of winter storms that are just as dangerous -During spring there are thunder storms Effects of Cyclones Effects Storm Surge -the highest surge will be where before it hits the coasts -the higher the wind speed the higher the hazard of surge -fetch: refers to the area over which the wind blows -large fetch results in larger storm surge -narrow bays and wide bays-high surges -impacts on surge elevations -ex. High tides -rising sea level -impacts how high the surge will be on the coast -when the surge reaches the channel it transports the sediment -overwash deposits due by high surge -overwash can create washover channels, isolating one area from another Heavy Rains -avg hurricane transports and produces precipitation -the flood is impacted by the amount of precipitation and elevation of the land -the longer the precipitation the more likely there will be flooding -the existence of natural barriers Linkages and Natural Services -coastal erosion creates natural processes and transports sediment -the speed fo the erosion inc -the flooding of an area -pollution -primary source of precipitation -redistrubute warm air from tropics -maintain ecosystems -winds carry plants, animals, and microorganisms -waves stir up deeper, nutrient rich waters -winds topple weak and diseased trees in forests -waves break apart some corals -natural selection, the some trees will not survive the high winds Human Interaction with Cyclones -as the pop inc, the hazards inc -coastal areas are more exposed to hurricane hazards -urban development, the higher the impact -seawalls are supposed to prevent mass wasting, they can create coastal erosion -engineering structures can only protect for a few years and have to be maintained -limits the amount of sediment movement -building materials and construction -global warming caused by human interaction -inc of temp will impact a body of water -surge will be higher -if we use technology to forecast better, and inform ppl about the impact of hurricanes, and what actions to take, maaaybe deaths will decrease -ppl still tend to move towards the coast -information system and media needs to lets us know the real and now of the number of losses -in the stats there needs to be more than just numbers. Why the inc of numbers? The inc population? Gathering info.. -what can cause the inc in numbers Forecasts and Warnings -watch: the hurricane will like happen -warning: hurricane will strike in 24 hrs or less -enforcing building codes -forecast: will be landfalls, where and when it will strike, winds strength, how much will be effected?, how big is the rainfall? How high is the surge -hurricane center in US and Canada -Doppler radar: can detect the path of the hurricane and how much rain. Records weather, collects data, wind speed, humidity, planes, temp, amount of precipitation -predictions are made -we cant completely trust those models because the wind speeds can always change -storm surge predictions: time and elevation of surge -the shape of the coast and the sea floor -precipitation of hazard depends on personal experience -new residents may underestimate the hazard -experienced ppl may take hazard ore seriously Adjustment to cyclones hurricanes and extratropical cyclones -how communities will adjust -there needs to be warning systems -maximize time of notification- adv notice -notice thru sirens -preparing ahead of time -shelter during the storm -insurance purchased ahead of time -flood insurance -where are the evacuation roads -supplies ready
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