weather hazards

• global atmospheric circulation:

  the movement of air around the earth to try and balance the temperature and air pressure
• how curvature of earth affects temperature:

  at equator earth is tilted so sun energy is concentrated there but is more spread out towards polar regions
• latitudes of the earth:

  north pole 60°N

  tropic of cancer 30°N

  equator 0°

  tropic of capricorn 30°S

  south pole 60°S
• global atmospheric circulation model part 1:

  • 90°N - 60°N (polar cell) 
  • polar easterlies (winds going down from east to west) 
  • 60°N - 30°N
  • prevailing westerlies (winds going up from west to east) (ferrell cell)
  • 30°N - 0°
  • trade winds (winds going down from east to west) (hadley cell)
  • 0° equator 
• global atmospheric circulation model part 2:

  • 0° - 30°S
  • trade winds (winds going up from east to west) (hadley cell)
  • 30°S - 60°S prevailing westerlies (winds going down from west to east) (ferrell cell)
  • 60°S - 90°S polar easterlies (winds going up from east to west) (polar cell)
• high pressure: cold air sinks, clear skies
• low pressure: warm air rises, clouds and rain
• tropical storm definition:

  a localised, very intense low pressure wind system, forming over tropical oceans with winds of hurricane force (120km/h) (250mm rain in a day)
• distribution of tropical storms:

  • 5-15° north and south of the equator 
  • NO TROPICAL STORMS AT THE EQUATOR because not enough rotation for one to occur
• where do hurricanes occur?

  atlantic and eastern pacific oceans (US and caribbean)
• where do cyclones occur?

  south pacific and indian ocean (south asia)
• where do typhoons occur?

  western pacific ocean (east asia)
• tropical storm formation step 1:

  • sea temperature at 27°C or higher 
  • ocean at least 70m deep
• tropical storm formation step 2:

  • warm air rises and condensation releases huge amounts of energy making powerful storm 
• tropical storm formation step 3:

  • area of low pressure increases surface wind
  • tropical storms move west because of trade winds 
• tropical storm formation step 4:

  • earths rotation causes storm to spin 
  • gets stronger as long as it's over water cause water is energy source
• Coriolis effect: the effect of the earth's rotation on the movement of air masses
• where tropical storms form:

  between approximately 5° and 30° latitude
• tropical storm development overview:

  • ocean water reaches at least 27°C, the air rises quickly, causing an area of very low pressure.
  • air continues to rise quickly, draws more warm moist air up from above the ocean leading to strong winds.
  • rising warm air spirals upwards, cools, condenses and large clouds form.
• after clouds form from warm air condensing:

  • they form the eye wall of the storm and produce heavy rainfall
• • in the centre of the storm, cold air sinks forming the eye of the storm - here, conditions are calm and dry.
• what happens when tropical storm reaches land?

  • they begin to lose their energy and die out
  • because they are no longer receiving heat energy and moisture from the ocean, which is needed to drive the storm.
• how climate change will affect tropical storms:

  distribution:

  • temperatures will be hotter therefore there will be more areas of the ocean that are over 27° which means more areas in the world will have tropical storms
  • example: south east coast of brazil was hit with first ever hurricane catarina in 2004 
• how climate change will affect tropical storms:

  frequency:

  • decrease in the future 

  intensity:

  • increase due to higher sea surface temperatures
• Typhoon Haiyan case study facts:

  • hit the Philippines in November 2013 
  • it was called Typhoon Yolanda in the Philippines 
  • category 5 on the saffir-simpson scale (over 157mph wind speed)
  • wind speed up to 170mph and 15m high p-waves
• Typhoon Haiyan primary effects:

  • 6300 people killed (most drowned)
  • 40000 homes destroyed 
  • 90% of Tacloban city destroyed 
  • 30000 fishing boats destroyed
• Typhoon Haiyan Secondary effects:

  • 14 million people affected 
  • 6 million people lost their source of income 
  • flooding caused landslides and blocked roads 
  • shortages of food water and shelter led to disease 
  • looting and violence broke out
• Typhoon Haiyan immediate responses:

  • US aircraft carrier, helicopters assisted with search and rescue as well as medical aid 
  • 1200 evacuation centres set up to help homeless 
  • Philippines red cross delivered basic food aid
• Typhoon Haiyan long term responses:

  • 'cash for work' programmes where people paid to remove debris and rebuild the city 
  • oxfam replaced fishing boats 
  • homes built away from areas at risk of flooding
  • more cyclone shelters built
• reducing effects of tropical storms:

  • prediction
  • monitoring
  • protection
  • planning
• prediction and monitoring:

  • gives more people time to act quickly 
  • allows government to differentiate between higher and lower areas of risk so different levels of protection in different areas 

  example: in North Atlantic two levels of warning:

  hurricane watch = advises that hurricane conditions possible

  hurricane warning = hurricane expected and people take immediate action 
• protection:

  • reinforcing buildings (strong concrete, stilts, stairs for safety to first floor, built on raised ground)
  • storm drains 
  • sea walls built 
• planning: 

  • raising individual and community awareness 
  • in USA there is National Preparedness Week
  • early warning systems (Bangladesh)