OCR GCSE Geography B: Global Hazards Tutorial

Introduction to Global Hazards

Global hazards are major extreme events that threaten people, places, and environments. These include climatic, geological, and hydro-meteorological events. Understanding these hazards is crucial for mitigating their impacts and managing risks effectively.

1. Global Atmospheric Circulation

Hadley, Ferrel, and Polar Cells

• Hadley Cells:
• Operate between the equator and 30° latitude.
• Responsible for the formation of tropical rainforests and deserts.
• Ferrel Cells:
• Located between 30° and 60° latitude.
• Drive mid-latitude weather systems, including depressions and fronts.
• Polar Cells:
• Exist between 60° latitude and the poles.
• Influence polar climates and high-pressure systems.

Pressure Belts

• Equatorial Belt: Low pressure due to high levels of atmospheric moisture and warmth.
• Subtropical Belt: High pressure formed by sinking air at 30° latitude.
• Subpolar Belt: Low pressure resulting from rising air at 60° latitude.
• Polar Belt: High pressure due to cold, sinking air at the poles.

2. Weather Extremes

Record Examples

• Wind: Cyclone Tracy (1974) in Darwin, Australia, reached winds of 250 km/h.
• Temperature: Death Valley, USA, recorded 56.7°C (134°F) in 1913.
• Rainfall: Mawsynram, India, receives over 11,777 mm annually.
• Drought: The 1930s Dust Bowl in the USA lasted over a decade.

3. Tropical Storms

Formation

• Sea Temperature: Requires sea temperatures above 27°C to a depth of at least 50 meters.
• Coriolis Force: Needs at least 5° latitude from the equator for rotation.
• Moisture: High levels of atmospheric moisture are essential for storm growth.
• Low Pressure: Area of low pressure forms over warm ocean waters.

Eye Structure

• Eye: Central region of calm weather, often 40 km in diameter.
• Eyewall: Surrounds the eye with the strongest winds and heaviest rainfall.
• Rainbands: Spiral bands of thunderstorms that extend from the eyewall.

Distribution

• Found between 5° and 30° latitude in all oceans.
• Most common in late summer and early autumn.

4. Drought Mechanisms

Causes of Drought

• Atmospheric Circulation: High pressure systems block rainfall.
• El Niño/La Niña Cycles: Alter global rainfall patterns.
• Human Activities: Overuse of water resources and land degradation.

El Niño/La Niña Cycles

• El Niño: Warm phase of ENSO (El Niño-Southern Oscillation).
• La Niña: Cool phase of ENSO.
• Impacts include droughts in Australia and floods in South America.

5. Case Studies

UK Drought 2012

• Causes: High pressure dominated the UK, blocking rainfall.
• Impacts: Water shortages, crop failures, and wildlife die-offs.
• Responses: Hosepipe bans and water rationing.

Typhoon Haiyan 2013

• Formation: Developed in the western Pacific Ocean with sea temperatures above 27°C.
• Impacts: Wind speeds of 313 km/h caused widespread destruction and over 6,000 deaths in the Philippines.
• Responses: International aid and long-term reconstruction efforts.

Conclusion

Understanding global hazards is essential for managing risks and reducing impacts. By studying global atmospheric circulation, weather extremes, tropical storms, drought mechanisms, and real-world case studies, you can better comprehend the complex interactions within our environment. Always remember the importance of preparedness and sustainable practices in mitigating these hazards.