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Storm Hazards (What does a cyclone look like (Spiralling storm features…
Storm Hazards
What does a cyclone look like
Spiralling storm features mass of cloud that surrounds central "eye" (5-50km diameter)
Eye= calm area, surrounding eyewall= wind speeds are strongest and causes most destruction
Converging air drawn in at surface as winds blow towards equator, heat from ocean surface causes air to be uplifted and drawn into storm
As air is blown over ocean it becomes warm enough to hold moisture and as it evaporated latent heat is released which provides energy to drive the storm and make it move
Without supply of heat and moisture the storm is deprived of energy, they decline quickly as move inland away from warm ocean surafce
Occur seasonally because much heat is needed to warm the ocean to 27 degrees to allow the storm to start, absence of tropical cyclones over S Atlantic and Pacific oceans and likely to do with presence of cooling ocean currents that depress surface temps
Once formed they track W across major oceans
Vulnerability of an area
Rural
Damage to buildings from strong winds, saturation of soil and landslides from heavy rainfall, crops destroyed from flooding and salinisation from storm surges
Upland
More landslides from steeper relief and saturated soil
Urban
Damage to buildings from strong winds, injury and death from flying debris, flooding due to impermeable surfaces
Lowland
Flooding from heavy rain, landslides move to lowland areas
LEDC
More damage due to poorly built structures which causes injury and death, less money to fix damage, poorly built infrastructure, less education and drills, less money to prepare
MEDC
Damage to more infrastructure, larger cities, tall buildings damaged by winds, larger and more urban areas causes more damage, economic losses= higher from strong winds and flooding
Coastal/ Inland
More powerful at coast, decays as moves inland= ports flooded
How do tropical cyclones form
Warm ocean temp more than 27 to provide continuous source of heat in order to maintain rising air currents
Ocean depth of at least 70m as moisture provides latent heat, rising air causes moisture to be released by condensation and continuation of this drives the storm
Winds in the lower atmosphere must be converging as winds have to come together ear the centre of the low pressure zone (low pressure= rising air)
Cross winds in the upper atmosphere to be gentle so the storm doesn't get ripped apart and allows it to form
Position in relation to equator to be 5-15 N/S in order that the Coriolis force can have maximum rotation of the air
Airflow in the upper atmosphere must be diverging to push away the warm air that has risen close to the centre of the storm to create a calm centre
Climate basics
Suns rays more concentrated at equator as they hit earth directly, at poles the curvature of surface and angle or rays means less heat and spread over wider area
Equator becomes warmer faster than poles so temp= higher at equator
When air is warmed by sun through conduction it will become buoyant and rise, when it cools it becomes denser and sinks
Warmer air holds more moisture and evaporation occurs, Cooler air holds less moisture so condensation occurs which forms clouds and causes precipitation, When evaporation occus Latent heat is releases as result of chemical change
Coriolis Force (spin of earth) linked to rotation of earth, when objects appear to be travelling straight they're actually curved. This effect causes surface winds to be defected. It is this force that causes tropical cyclones to spin anti-clockwise in NH and clockwise in SH
Saffir-Simpson scale
(1) 74-95mph winds, Some damage
(2) 96-110mph winds, Extensive damage
(3) 111-129mph winds, Devastating damage
(4) 130-156mph Catastrophic damage
(5) 157mph +, Catastrophic damage
Impacts
Strong Winds
Damage to buildings and vegetation/ crops, damage to shipping and offshore structures
Storm Surges
Flooding of low-lying coastal areas, erosion of cliffs and coastal areas exaccerbated
Heavy Rainfall
Flooding of low-lying coastal areas, flooding of inland areas near rivers
Landslides
Heavy rainfall saturates material, coastal erosion undermines cliffs
Frequency, magnitude, predictability
Occur at certain times of year= quite predictable
Magnitude varies on Saffir-Simpson scale based on wind speed, air pressure, storm surge potential and also potential damge
Management
MEDC
Mitigation and Prevention
Land use planning, not really preventable, hazards resistant design, cloud seeding
Protection/ Adaptation
Land use planning, community preparedness, evacuation, drills, shelters, warning systems, sea walls, defences
Preparedness
Warning systems, forecasting, US government funded national hurricane centre which looks for developments, Computer forecasting, Evacuation, 24hrs prior can make accurate prediction, community preparedness, education
LEDC
Mitigation and Prevention
Limited money and technology, some hazard resistant design, some land use planning, limited as developing economy
Protection/ Adaptation
Education, drills, community preparedness, shelters, evacuation procedures
Preparedness
Education, community preparedness, evacuation, limited technology
Nature and spatial distribution
Between 30N and 30S