CAMBRIDGE GEOGRAPHY A2 REVISION - HAZARDOUS ENVIRONMENTS: HAZARDOUS ENVIRONMENTS RESULTING FROM ATMOSPHERIC DISTURBANCES. Presentation suitable for Cambridge A2 students. It contains: key terms and definitions, topic summary, additional work and suggested websites.

1. A2 GEOGRAPHY REVISION
HAZARDOUS ENVIRONMENTS
9.3 HAZARDOUS ENVIRONMENTS
RESULTING FROM ATMOSPHERING
DISTURBANCES

2. KEYTERMSANDDEFINITIONS
Fujita Scale is a scale devised by Dr Theodore Fujita to measure damage done
by tornadoes. It varies from T0 (winds less than 73 mph) with little damage,
to F5 (winds greater than 261 mph) with ‘incredible damage’.
Mesocyclone is a large-scale region of rotation, typically around 3–8 km in
diameter and often found in the rear flank of a supercell. The circulation of a
mesocyclone covers an area much larger than the tornado that may develop
within it.
Supercell tornado is a tornado associated with large, long-lived
thunderstorms, possessing strong mid-level rotation. (Nonsupercell
tornadoes are smaller but may still contain damaging winds in excess of 120
knots.)

3. KEYTERMSANDDEFINITIONS
Tornado is a violent, destructive weather system, with powerful rotating
winds (up to 300 km/h).
Tornadoes are intense low pressure systems, and their development depends
on instability in the atmosphere, convergence and strong updrafts in the air.
Vortex is a whirling and rising mass of air and cloud in a tornado.
Hurricane is a tropical storm that forms over the North Atlantic, with winds
over 74 mph (120 km/h).
Tropical cyclone is the generic name to include hurricanes (North Atlantic),
cyclones (Indian Ocean and the Bay of Bengal) and typhoons (Japan). A
tropical cyclone is a low-pressure system commonly up to 600 km in diameter
with wind speeds of up to 300 km/h (typically 160 km/h) and bringing up to
30–50 cm of rainfall.

5. TOPICSUMMARY
Hurricanes are intense hazards that bring heavy rainfall, strong winds and
high waves, and cause other hazards such as flooding and mudslides.
● Hurricanes are the most violent and frequent hazard to affect many
tropical regions.
● Damage is caused by high winds, floods and storm surges.
● The Saffir-Simpson Scale measures a hurricane’s intensity.
● The unpredictability of hurricane paths makes the effective management
of hurricanes difficult.
● National governments can help prepare for a hurricane through risk
assessment, land-use control, floodplain management and reducing the
vulnerability of structures.

6. TOPICSUMMARY
Tornadoes are small and short-lived but highly destructive storms.
● Tornadoes consist of elongated funnels of cloud that descend from the
base of a well-developed cumulonimbus cloud, eventually making contact
with the ground beneath.
● Moisture, instability, lift and wind shear are the four key ingredients in
tornado formation.
● The most destructive and deadly tornadoes occur from supercells;
rotating thunderstorms with a well-defined low pressure system called a
mesocyclone.

8. TOPICSUMMARY
A tornado’s impact is threefold: first, the winds are often so strong that
objects in the tornado’s path are severely damaged; second, strong
rotational movement tends to twist objects from their fixing, and strong
uplift can carry some debris upwards into the cloud; and third, the very low
atmospheric pressure is a major source of damage.
● Although winds from the strongest tornadoes far exceed those from the
strongest hurricanes, hurricanes typically cause much more damage
individually and over a season, and over far bigger areas.
● The Fujita Scale relates tornado damage to the intensity of the wind.
● There are limited ways of dealing with a tornado other than staying
indoors and staying under cover.

11. ADDITIONALWORK
1. Outline the conditions necessary for the formation of hurricanes.
2. Outline the main hazards associated with hurricanes.
3. How does the impact of hurricanes vary with levels of economic
development?
4. To what extent is it possible to manage the impacts of hurricanes?
5. Explain the main hazards associated with tornadoes.
6. Describe, and suggest reasons for, the distribution of tropical storms
(hurricanes).
7. To what extent is it possible to manage the impacts of hurricanes and
tornadoes

12. SUGGESTEDWEBSITES
http://coastal.er.usgs.gov/hurricanes/ivan/ for Hurricane Ivan impact
studies.
http://coastal.er.usgs.gov/hurricanes/jeanne/ for Hurricane Jeanne impact
studies.
http://coastal.er.usgs.gov/hurricanes/charley/ for Hurricane Charley impact
studies.
http://coastal.er.usgs.gov/hurricanes/charley/lidar.html shows the breach
in the barrier islands caused by Hurricane Charley.
http://coastal.er.usgs.gov/hurricanes/isabel/ for the effects of Hurricane
Isabel