Global Hazards- Weather Hazards

Winds

• Caused by different air pressures
• Large scale air movements 
• Move from high pressure areas to low pressure areas
• Trade Winds- blow from SE in the southern hemisphere and NE in northern hemisphere
• Westerlies- blow from NW in southern hemisphere and blow from SW in northern hemisphere

Global Atmospheric Circulation

• 3 Circulation Cells - Hadley, Ferrel, Polar
• Low pressure belt - Rising air, Clouds, Minimal rainfall

Global Climate Zones

• Arid - High pressure belt caused by sinking air from 2 cells meeting at 30 degrees north and south of the equator (Low rainfall)
• Tropical - Low pressure belts caused by rising air from 2 cells meeting near equator (High rainfall and high temperature)
• Temperate - Low pressure belt caused by rising air from 2 cells meeting at 60 degrees north and south of equator (Frequent rainfall and moderate temperature)
• Polar - Low temperature

Extreme Weather

• Winds - Cape Town
• Temperature- Sahara Desert
• Rainfall- Amazon Rainfall

Tropical Storms

• Spin caused by earths rotation
• Strength increases when storms move over warm water
• Develop over warm water
• Frequent distribution of tropical storms
• Strength decreases when stroms move over land or cool water
• Most happen in late summer and autumn
• Most happen between 5 and 30 degrees north and south

Drought

• Anticyclones are capable of blocking depressions (weather systems that cause rain)
• Frequency of droughts has remained fairly constant but distriution has changed alot.
• Main causes - Changes in atmospheic circulation, blocked depressions

• Distribution - Strong threat for central and southern Africa, Australia, Middle East, western South America and patches of North America.