GEOL110_Natural Hazards CH10
GEOL110_Natural Hazards CH10 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 3 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 Katrina (video) -gulf of Mexico invaded the land Low and High Pressure Centers -Air movement can cause changes I pressure -convergence occurs when air flows in increasing pressure -coming winds -divergence occurs when air flows out decreasing pressure -winds that are leaving -at surface, air moves from surface high pressures (H) to low pressures (L) -Air at low rises into atmosphere and then diverges in the upper atmosphere -A surface L associated with H at top -circulate and create higher pressure -higher pressure moves from high to lower pressure -winds are sinking and moving from the higher altitude -lower pressure raising winds up -higher pressure on northern hemisphere Cyclonic movement -jet streams affected by cyclonic movement Unstable Air -when the temp of air is higher than the surrounding -tendency of air is to remain in place -atmospheric stability -air parcels resist movement, thus return to original spot after them move -in unstable air, particles are rising until they reach air of familiar temperature and density -air is unstable when lighter, warm or moist air is overlain by denser cold or dry air -some air sinks and some air rises -colder air moves downward -the temp depends on the amount of humidity -instability causes weather systems and is the cause for the formation of weather systems Circulation -heat Fronts -if different masses of air (cold, dry..) they depend on weather they are above land or ocean -boundary between cooler and warmer air masses -air masses don’t mix -warmer air will always be lifted by the colder, denser air masses -air masses also have different humidity levels, densities, wind patterns, and stability -different fronts -cold front when cold air is moving into warm air -warm front when warm air is moving into cold air -stationary front where boundary shows little movement -when masses aren't moving -there is cold and warm air not moving -occluded front where rapidly moving cooler air overtakes another cold air mass wedging warm air in between -warm and cold mass came together and picked up the 3 mass of air up -picked up a warmer mass upward -warm air approaching cold air -cold air moving slowly, warm moving faster -cumulus clouds forming Thunderstorms -most occur in equatorial regions -most common in the afternoon or evening, in spring or summer -3 conditions necessary 1.warm and humid air available in lower atmosphere 2.steep vertical temp gradient such that the rising air is warmer then the air above it 3.updraft must force air up to the upper atmosphere -Formation -most air is forced upwards, cools and water vapor condenses to form cumulus clouds -updraft: movement of air upwards -Stages 1.Cumulus stage - uplifts -moisture supply and updrafts cont. clouds grow -a continuous release of latent heat from condensation warms the surrounding air causing the air torise further -precipitation one of two mechanisms 2.Mature stage - up and down -drafts -downdrafts and falling precipitation… -1.Air mass thunderstorms -most individual thunderstorms -last less than 1 hr and do little damage -2. Severe Thunderstorms- classified by national weather service: -winds > 93 km (53 mi) per hour -hailstones > 19 cm -generates a tornado -Necessary conditions -large changes in vertical sind shear, greater shear greater storm -high water vapor content in lower atmosphere -mesoscale convective systems (MCS) -can last > 12 hrs -most common -clusters of self propagating storms -one cell downdrafts forms another nearby -squall lines -common along cold fronts -updrafts from cumulonimbus -lines of individual cells with cumulonimbus.. -Lightning -common during thunderstorms -flashes of light due to discharge of millions of joules of electricity -extreme heat causes air to rapidly expand - thunder -cloud to cloud more common -cloud to ground less common -hail: hard, round, irregular pieces of ice originating from thunderstorms -contain rings due to adding coating during updrafts -hail moves up and down in lower part of the storm adding layers of liquid water which then freezes -cause mostly property damage -on avg - 41 billion a year in the US -most common locations -North Am: great plains in US, Calgary region of Alberta, Canada -other regions: North- central India, Bangladesh… Hazardous Weather and Geographic Regions at Risk -severe weather refers to: Tornadoes -triggered by severe thunderstorms -most violent natural processes -1992-2992 killed avg of 62 ppl / yr -shapes: rope, funnel, cylinder, wedge -defined by vortex extending downward from the cloud and touching the ground -called funnel clouds when it doesn’t touch the ground -1. organizational stage -vertical wind shear: develops rotation -strong updrafts: tilt the horizontally rotating air vertically (mesocyclone) -wall cloud rotates and funnel descends -2. Mature Stage -visible condensation funnel extends to ground -moist air drawn upward -suction vortices - greatest damage -3. shrinking stage -not enough supply of warm air -more dangerous cuz wind speed inc as diameter decreases -4. rope stage -downwards cause tornado to form Enhanced Fujita Scale of Tornado Intensity -classification of tornadoes - according to most intense damage -assigned value of enhanced Fujita Scale - levels of damage of buildings, trees and wind gusts -water spouts : tornadoes on the lake Tornadoes - Occurrence -everywhere, most common in the US -right combination of weather, topography and geographic location -Midwestern states btwn Rocky Mounts and Apps -Spring and summer in late afternoon and evening are most common -highest risk is in tornado alley - north to south thru the Great Plains -also, Canada -include Alberta, S Ontario -waterspouts Blizzards and Ice Storms -Blizzards -severe winder storms with large amounts of falling or blowing snow high winds, low visibility for extended period of time -whiteout- extremely low visibility -official thresholds differ -ground blizzard -high winds picking up previously fallen snow -causes of blizzards -upper-low with surface -low interaction Colorado and coastal storms - from moist ocean air -Alberta clippers are drier, less snow and cold temp -Nor'easters on East Coast have hurricane force winds, heavy snows, intense precipitation, and high waves -wind shill- quick frostbites -wind cools skin, evaporates moisture, reduces time of frostbites, thus blizzards dangerous -Ice Storms -prolonged periods of freezing rain -upon contact with cold objects, rain freezes forming ice coat -during winter on the north side of a stationary or warm front -3 conditions for freezing rain -source of moisture -warm air over shallow cold air -objects on land close to or at freezing Thickness of Cold Air Determines Precipitation Type -formation of fog -development -humidity condenses -in the warmer air, it can absorb more water vapors -cold air gets humid faster because it cant absorb water vapors -colder air absorbs less water vapors -excess of water vapor changes into water droplets forming fog Fog -a cloud in contact with ground -air cooling to condensation -adding water to cooled air thru evaporation -cooling -at night heat radiates from land -warm air blows over cold water -humid air rises up a mountain side -Evaporation -cold air flows over warm body of water -warm rain falls thru cool air Drought -extended period of low precipitation -produces a shortage of water, food and power shortages -affects more ppl than any other natural hazard Mountain Windstorms -develop seasonally - downwind side of mountain ranges or glacial ice fields -mountain block prevailing winds, cause winds to move quickly down slopes -contribute to large wildfires, damage roof and tree, blow cars off highways Dust Storms and Sandstorms -Dust storms -strong windstorms with dust -reduce visibility -several hundred kilometers -carry 100 million tons of dust Heat waves -long period of extreme heat -associates with high pressure called ridges -wet conditions to the west or ridge -dry conditions… Human Interaction with Weather -Land Use hazards -agriculture leaving topsoil exposed - dust storm -location of mobile homes in high winds / tornado area -global warming can inc Linkages with other Hazards -short term events -flooding -slow moving thunderstorm producing a lot oof rain in a relatively short time -stagnation of thunderstorms - storms back over the same area -comes from precipitation and surge of water from the coast -mass movement -wildfires -can start from lightning -long term changes in global climate -drought, dust/sandstorms and heat waves -tropical and extratropical cyclones Natural Service Functions of Severe weather -contribute to health of forests -wildfires clear old growth -windstorms topple dead trees -source of water Forecasting and predicting weather hazards -timely and accurate prediction is extremely important to space human lives -event still difficult to forecast -behavior is unpredictable -Doppler radar can predict paths -detects clouds, rain, ice particles… -uses wavelength of reflected waves to determine directions -for short term predictions -detection of mesocyclone Adjustment to the Severe Weather Hazard -cant prevent severe weather, but can take steps to reduce associate death and damage -mitigation -long term actions to prevent or minimize death, injuries and damage are considered mitigation -different for each weather hazard but some general techniques -building new structures -ensuring utilities can cont to funct in sever weather -warning systems -hazard insurance -preparedness and personal adjustments -many should be carries out b4 a watch or warning is issued -know your climate and when hazards are most likely -prepare your home for likely hazards -get info -NOAA, FEMA -wear proper clothing -modify travel plans