9.3 Hazards resulting from atmospheric distrubances Flashcards
define risk and vulnerability - differences
risk: probability hazard event causing harmful consequences
vulnerability: susceptibility to a hazard
factors determining risk
location
wealth
time
type of hazard
factors determining risk perception
- the subjective judgement that people make about the characteristics and severity of a risk
- Experience: make you more or less
- material well being
- personality
similarities and differences between hurricanes and tornadoes
Similarities:
- strong winds
- high energy environment
- rotating motion
- eye
- cause damage
Differences:
- wind speed (strongest tornado has stronger winds than hurricane, but generally hurricanes stronger)
- hurricanes have a greater diameter (size)
- hurricanes form above water
- easier to predict/track a hurricane
- other hazards associated with hurricanes (storm surge)
- location: hurricanes only in tropical/subtropical areas but tornadoes can form anywhere
- tornado local/short lived; cyclones longer duration
- tornado touches ground, hurricanes remain in atmosphere
global distribution of hurricanes and tornadoes
hurricanes:
- around equator largely with category 5 concentrated on south east coast of Asia: western pacific most intense
- tropical region not equator itself: 5-30 degrees above/below
- more in northern hemisphere than southern
tornadoes:
- mainly north America but can occur anywhere
- everywhere but Antarctica
area most at risk from hurricanes
- south east Asia:
- high population density
- wealth inequality: informal settlements won’t withstand strong winds
- rely on aid to recover
- frequency of hazards high
- islands: hard to be evacuated/receive help
formation of a hurricane
- warm sea surface heats air above it which causes it to rise (forming low pressure) and then cools/condenses to form rain - much more rain due to quick rising air by warm sea surface
- as water changes state, latent heat transfer fuels rising of air even more
- low pressure can lift up the water
- as air rises, more air rushes in to replace the air that rises upwards - generating strong winds
conditions needed for a tropical storm to form
- cluster of thunderstorms over warm ocean
- high levels of moisture
- low wind shear: winds are at same speeds/low hurricane can form
- 26.5 degrees
- strong winds - 74mph
- unstable air pressure: high levels of moisture, usually where areas of high/low pressure meet (convergence)
when do tropical storms form
- between may and november in northern hemisphere and november and may in southern hemisphere
- as when the noonday sun is high and so long period of intense heating to warm sea temps
where do tropical storms form according to latitude
- 5to 30 degrees north and south as do not form nearer the equator because coriolis effect needed to deflect the converging rising air into a spin and effect of earths rotation not strong enough near equator
- in higher latitudes sea not warm enough for their formation and there are no strong upper atmosphere winds in these latitudes so air can rise to tropopause
importance of latent heat in the formation of hurricanes
- as rising air cools to below dew point, condensation releases latent heat
- this causes the air to rise even faster, low pressure to lower even more and the moisture-laden wind to rush into the low pressure centre even faster
- lower the pressure, the more air is drawn into it and greater its power
- very heavy rain falls from thick cumulonimbus clouds produced by the uplift
conditions of the eye wall
- very dense circular band of cumulonimbus cloud
- most powerful winds and deepest convection with towering rain clouds that above the rest of the cyclone due to vast amounts of latent heat released from them
factors that affect the impacts of hurricanes
population density
politics
warnings
level development
size/category/nature of the storm
risk perception
track of the storm
frequency of the hazard
how does frequency of hazard affect the impacts of hurricanes
- higher frequency = less time to recover and so put in reinforcements if very close together
- e.g Katrina first of three high category storms to hit central Gulf in quick succession
- although higher frequency = more aware of severity/know what to expect and so likely to have more plans in place
- e.g hurricane sandy was the 18th named storm to hit USA that season
how does track of the storm affect impacts of hurricanes
- impact on warning:
- e.g path of Hurricane sandy affected by unusual atmospheric condition and moved west instead of east and hit New York
- only 2 day forecast
how does risk perception affect impacts of hurricanes
- lower levels of wealth likely to be more afraid as whole livelihood ; higher levels of wealth who have secure infrastructure/able to evacuate/insurance less worried
- links to frequency: more frequent may be more aware of severity but also then may choose to stay if previous experience bad when leaving
how does size/category/nature affect impacts of hurricanes
- physical factors that aren’t affected bu development e.g location/size:
- harder to evacuate/receive aid if an island`
- storm surge very difficult to protect against = high damage: e.g hurricane katrina: 80% of New Orleans below sea level/only protected by levees which could not withstand surge causing 8m deep flooding
- larger size = more areas affected e.g Hurricane Sandy 1800km in diamter despite only category 2
how does level of development affect impacts of hurricanes
- lower=higher population density/more likely to live by coast (more exposed), more primary industry and so reliant on agriculture - loss of land - detrimental impact economically: e.g 70% of Honduras economic output lost and took longer to recover as mainly primary compared to New York*
- more developed = stronger/better infrastructure to withstand storm, but may result in higher cost of damage if unable to withstand storm
- less developed: less knowledge on how to prepare/communicate with authorities
how do warnings affect impacts of hurricanes
- higher wealth = higher level of tech to predict/communicate with people: higher education = understand whats happening/know what to do
- length of warning = more time to prepare/evacuate: 2 day forecast in New York for Hurricane sandy not long enough
- errors made in warnings e.g hurricane sandy: no warnings in New Jersey so not aware of severity as not expected to hit
- if certain hazards not expected then not prepared in correct way, e.g constant rain in Hurricane Mitch unexpected: most damage caused by floods and mudslides
how does politics affect impacts of hurricanes
- dictatorships may prevent aid from being received or even warnings: e.gBurmese people received no warning of hurricane
- limit successes of aid e.g Cyclone Nargis, military junta prevented aid arriving: lack of response cost 1 million lives
- in contrast hurricane sandy: Obama signed emergency declarations for states expected to be impacted by Sandy allowing them to request federal aid/prepare.
How does population density affect impacts of hurricanes?
- urban vs rural, more populated = more impacted in one area: e.g Hurricane Mitch large areas of informal housing hit as often on marginal land - prone to landslides
