Global Hazards

• hemisphere


  a half of the earth, usually as divided into northern and southern halves by the equator

  
• weather


  The condition of Earth's atmosphere at a particular time and place. (eg, temperature, precipitation, cloud cover)
• climate


  The average (expected) weather conditions in an area based on data collected over 30 years or more.
• troposphere


  the area of the atmosphere from the Earth's surface to a height of 10-15km in which the weather takes place

  
• climate zone


  divisions of the Earth's climates into belts or zones, according to average temperature and average rainfall. The three major zones are polar, temperate and tropical.

  
• latitude


  the imaginary lines that surround the earth ranging from 0° at the equator to 90° at the poles

  
• atmospheric air pressure


  The force exerted on the Earth's surface by the weight of the air, measured in millibars.

  
• low pressure


  caused when air is rising, so less air is pressing down on the ground; air rises as it warms, leading to low pressure at the surface.

  
• high pressure


  when there is more air pressing down on the ground, caused by air sinking; air descends as it cools, leading to high pressure at the surface.

  
• condensation


  the process by which rising water vapour becomes a liquid.

  
• precipitation


  the collective term for moisture that falls from the atmosphere; this could be in the form of rain, snow, sleet or hail

  
• Hadley cell


  a system of vertical and horizontal air circulation that creates major weather patterns, predominantly in tropical and subtropical regions

  
• Ferrel cell


  air circulation cell found at midlatitudes (between 30° and 60°) between Hadley and Polar cells.

  
• Polar cell


  air circulation cell found between 60° and 90°, air rises at lower latitude and sinks at poles.

  
• front


  a boundary separating two masses of air with different densities, usually heavier cold air and lighter warm air.
• trade winds


  the prevailing pattern of easterly surface winds found in the tropics within the lower section of the Earth's atmosphere.
• prevailing wind


  the most frequent, or common, wind direction

  
• rain shadow


  an area or region behind a hill that has little rainfall because it is sheltered from rain bearing winds.

  
• monsoon


  heavy rainfall that arrives as a result of seasonal wind, notably in southern Asia and India between May and September.

  
• Katabatic wind


  movements of cold dense air that flow downhill and along valley floors; in Antarctica, most winds blow towards the coast from the centre.

  
• El nino


  climatic changes affecting the Pacific region and beyond every few years, characterised by the appearance of unusually warm water around northern Peru and Ecuador, typically in late December; the effects include the reversal of wind patterns across the Pacific, causing drought in Australasia and unseasonal heavy rain in South America.

  
• thermocline


  the point at which the temperature changes from warmer surface waters to deeper, colder water.

  
• drought


  a prolonged period of time with unusually low rainfall; occur when there is not enough rainfall to support people or crops.

  
• La nina


  A climate event in the eastern Pacific Ocean in which surface waters are colder than normal.

  
• tropical storm


  a strong depression (low pressure system) with wind speeds of between 39-74 mph, usually form over tropics where water is warm.

  
• Coriolis effect


  the result of Earth's rotation on weather patterns and ocean currents, making storms swirl clockwise in the southern hemisphere and anticlockwise in the northern hemisphere

  
• intertropical convergence zone


  a low-pressure belt that encircles the globe around the Equator; its is where the trade winds from the northeast and southeast meet; the Earth is tilted on its orbit around the Sun, causing the ITCZ to migrate between the Tropics of Cancer and Capricorn with the seasons.

  
• heatwave


  a prolonged period of abnormally hot weather

  
• super typhoon


  a storm that reaches sustained wind speeds of at least 150 mph.

  
• Emerging and developing country


  a country which neither shares all the economic development characteristics required to be advanced or are eligable for the Poverty Reduction and Growth Trust; EDCs are classified by the IMF
• primary industry


  an economic activity that involves collecting raw materials, such as fishing, farming and mining

  
• inner core


  the centre of the earth with a solid metal inner core (at 6000°C temperature) composed primarily of iron and nickel

  
• outer core


  semi-solid outer core (4030° - 5730°C) from which heat is radiated outwards from the core to the mantle

  
• mantle


  hot, dense liquid rock (magma); it is continuously moving due to heat from the core (convection), which drives plate movement.

  
• crust


  the solid, rocky shell layer (lithosphere) over the mantle around the Earth, upon which sit our continents and oceans; it is fragmented into tectonic plates that float on the mantle.

  
• radiation


  energy transfer process by which energy is emitted outwards from a central point in waves or rays.

  
• convection


  the constant churning of the mantle through heat energy (radiation) passing out from the core

  
• tectonic plate


  Section of the Earth's crust that move due to convection currents. (7 major and many small or micro)

  
• oceanic plate


  the lithosphere (crust) which is underneath oceans. Thinner, denser, newer, able to be subducted, destroyed and created

  
• continental plate


  the lithosphere (crust) upon which sits our continents and land. Thicker, less dense, older, unable to be subducted, or renewed.