9.3 hazards resulting from atmospheric disturbances

Question 1

large-scale tropical disturbances: tropical cyclones

Answer 1

• Atlantic, Caribbean, N-W Pacific: hurricanes
• N-W Pacific, Indian Ocean, S Pacific: tropical cyclones
• size, longer duration, variety of ways they cause damage
• bring intense rainfall, very high winds, storm surges, coastal flooding, mass movement, inland flooding
• their path is erratic: not always possible to give 12+ hour warning
• move excess heat from low latitude to higher
• normally develop in the westward-flowing air just north to the equator (easterly wave)
• 10% of tropical disturbances become storms

Question 2

formation of tropical cyclones

Answer 2

1. Ocean water above 27 C for evaporation: warm water rises creating a low pressure zone
2. minimum 50-60M deep as storms stir up ocean bringing up cold water
3. cross winds need to be coming together, converging near the surface
4. humid air up to 5500m cools, condenses forming clouds releasing latent heat energy: unstable airmass continues rising
5. Coriolis effect creates rotation in rising air mass/too close to equator: no Coriolis: NW to NE
6. upper atm high pressure area helps pump away rising air in the storm
7. becomes a hurricane when winds exceed 119km/h, pressure as low as 880mb

Question 3

tropical cyclones hazards

Answer 3

• loss of electricity:no heating:health issues
• death/injury
• flooding
• loss of property
• psychological impact
• issues with water supply
• loss of production
• insurance cost
• communication issues
• sewage contamination

Question 4

tropical cyclones factors

Answer 4

• unpredictable paths: Jamaica Hurricane Ivan 2004 changed from densely populated area
  -greatest storm not equals greatest damage
• distribution of population: Caribbean islands many live exposed to risk
• mitigation depends on urban planning laws, emergency planning, evacuation plans/measures, relief operations like rehousing
• LICs lose more lives due to inadequate planning and preparation while costs are greatest in areas like Florida with multi-million pound waterfront homes

Question 5

tropical cyclones management

Answer 5

• satellite images
• aircraft that fly into the eye of the storm to record weather info
• weather stations at ground level
• radars that monitor areas of intense rainfall

Question 6

prep

Answer 6

• vulnerable housing: owners encouraged to fix tropical storm straps to roofs and storm shutters over windows, houses on stilts allow flood water to pass
• Hurricane Luis (1995) damaged 90% of Antigua’s houses

Question 7

land use zoning

Answer 7

• aim is to control land use so that the most important facilities are placed in the least vulnerable areas

Question 8

risk assessment

Answer 8

• evaluation of risk can be shown in a hazard map, info may be used to estimate probability of cyclones
• analysis of climatological records for time, intensity, location
• history of speeds, frequencies, flooding, height

Question 9

floodplain management

Answer 9

• to protect critical assets from flash/riverine coastal flooding

Question 10

reducing vulnerability of structures and infrastructures

Answer 10

• new building winds and water resistant: building codes
• communication and utility lines away from coast/underground
• raising ground level
• mangroves, embankments, levees
• increased vegetation cover to reduce impact of soil erosion and landslides and to facilitate absorption of rainfall

Question 11

tornadoes: smaller scale

Answer 11

vertical funnels of rapidly spinning air connecting the ground and clouds

Question 12

supercells

Answer 12

• warm humid air collides with cold dry air
• cold air is pushed above
• air starts to blow cyclically vertically to the ground to balance out pressure
• updraft lifts rolling pipe of wind upright: reaches clouds pulling condensed water vapour from clouds: upright spinning vortex
• few hundred m in diameter lasts for mins- hours

Question 13

tornado locations

Answer 13

• temperate continental interiors in spring/early summer when air may be unstable
• NW in Minnesota, SE in coastal S Texas
• tropical storms in Texas or NW-flow weather systems in upper Midwest

Question 14

tornado hazards

Answer 14

• intense ppt especially hail
• strong/high winds
• pressure imbalances
• kill avg 60 people/year from flying debris
• winds are strong + rotational movement tends to twist objects in their fixing, strong uplift carry debris up to clouds
• low atm p near vortex decreases internal pressure, walls and roofs may explode outwards in process of equalising pressure differences

Question 15

tornado vs cyclone

Answer 15

• although strongest tornadoes max exceed those in strongest tropical storms, cyclones cause more damage individually, over a season and far bigger areas
• economically tornadoes cause 1/10 damage to cyclones

Question 16

tornado management

Answer 16

• underground shelter: small room or closet

Question 17

Texas northwards

Answer 17

• known as tornado valley
• interaction between hot humid air from the Gulf of Mexico and cold air from the northern interior of north america: supercell

Question 18

non super cell tornadoes:

Answer 18

• warm high P air meets low P warm air near ground level, winds start blowing cyclically, turn into upright spinning vortex, updrafts lift up to clouds​
• Tornado: cloud connected to ground​