Geography A2 Notes

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Hurricanes

What are Tropical Storms:

* Large rotating storms around a centre of very low pressure. * May be 800km across and 12km high
* Wind speeds may reach 180km per hour.
* High intensity, high volume rainfall (up to 500mm in 24hr)

There are also known as:

* Hurricanes (North Atlantic)
* Cyclones (Indian Ocean and the Bay of Bengal)
* Typhoons (Western Pacific)
* Willy Willies (unique to Australia! Although often still called cyclones e.g. Cyclone Tracey)

The conditions required for Hurricanes to form:
* Sea temperatures greater the 27’C for a significant period of time and over a depth of at least 50m) * Sufficient spin from the earth’s rotation (Coriolis effect) to trigger the vicious spin in the centre of the hurricane (5’-30’ north and south of the equator)

The cross section of a hurricane:

Hurricanes can be monitored easily through:
* Satellite technology.
* Advanced meteorological technology

Links

Animation of the formation of a Hurricane

Hurricane Sandy Case Study

Hurricane Katrina Case Study

Tornadoes

* Tornadoes are a complex phenomena and little understood, yet one of the most destructive. * The country with the greatest density per km square is the UK. * The highest number of deadly tornadoes is found in Tornado Alley, USA.

What is a tornado:
* A vortex (whirling mass of air)descends from well developed cumulonimbus cloud. * A tornado vortex is in contact with the cloud and the ground * Violent winds (100m per second)
* Extreme pressure gradients (25mb per 100m) and air rushing from the high to low causes the spinning winds. (Hurricanes 20mb per 100km!!) * Diameter of funnel is rarely more then 200m

Key conditions required for a tornado to form:

* Moisture
* Warmth
* Lift
* Wind shear

Tornado Risk map USA

Tornado frequency map USA

Tornado Hazard Impacts

* Strong winds move/damage objects in their path
* Rotation/twist of objects can cause high lifting and flinging of objects over a wider area. * Potential ‘explosion of buildings’ as pressure is equalised when vortex passes.

Fujita Tornado Damage scale

* Relates the degree of damage to wind intensity.
* Caution: does not take into account differences in building structure/design. * Since 2006, the Enhanced Fujita Scale has been used. Combines damage scale F0-F5 with engineering expertise into how different buildings/structures can react to tornados

Atmospheric Systems

Climate Hazards in UK
Cold
* Heavy rain
* Flash floods
* Hail
* Lightening
* Snow in Winter Blizzards
Cold
* Heavy rain
* Flash floods
* Hail
* Lightening
* Snow in Winter Blizzards
Hot
* Drought
* Heat waves
* Heavy thunderstorms
Hot
* Drought
* Heat waves
* Heavy thunderstorms

Example: Carlisle Flood 2005

Temperate Climate

* UK Temperate Climate
* Does not experience extremes of temperatures.
* Precipitation throughout the year.
* Very unpredictable!!
* Average summer temperature 18 degrees centigrade
* Average winter temperatures between -2 and 7 degrees centigrade.

* Main influences on UK
* Its latitude; 50 to 60 degrees north
* Its Maritime position; surrounded by sea: Atlantic, The Channels, North Sea * Prevailing wind direction which is southwest and this is governed by the atmospheric circulation system * Air masses big influence causing major weather patterns!

UK Weather
Points to consider:
* Layers of the atmosphere.
* Jet stream is high altitude strong wind; near the top of the troposphere. * The Polar and ferrel cells

Air masses

* Large bodies of air, often thousands of km wide
* Air masses derive their temperature and humidity from the regions over which they form; known as source regions. * Source areas are areas of high pressure and high winds and...
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