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A2 CAMBRIDGE GEOGRAPHY: HAZARDOUS ENVIRONMENTS - HAZARDS RESULTING FROM ATMOSPHERIC DISTURBANCES. It contain case studies: Hurricane Katrina 2005, Cloud Seeding in New Zealand 1950-1970.

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  2. 2. LEARNING OBJECTIVES Global distribution of areas most at risk from large scale tropical disturbances (cyclones, hurricanes, typhoons) and small scale atmospheric disturbances (tornadoes). Processes causing the formation and development of cyclones, hurricanes, typhoons and tornadoes. Hazards from large scale atmospheric disturbances: storm surges, coastal flooding, intense rainfall leading to severe river floods and mass movement, and high winds. Hazards from small scale atmospheric disturbances: intense precipitation (rain and hail), high winds, and pressure imbalances. Primary and secondary impacts on lives and property. Prediction, preparedness and monitoring of large and small scale atmospheric disturbances and perception of risk.
  4. 4. TROPICAL DISTURBANCES A tropical disturbance forms over waters of at least 26.5C. A tropical disturbance is defined as an area of organized thunderstorm activity 100 - 300 miles in diameter which maintains its identity for 24 hours or more. In meteorology, a tropical disturbance can be defined as a very weak, or incipient (just beginning), tropical cyclone.
  5. 5. TROPICAL CYCLONES A tropical cyclone is a rotating storm system characterized by a low-pressure centre, a closed low-level atmospheric circulation, strong winds, and a fast spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone.
  6. 6. HURICANES, TYPHOONS, CYCLONES A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and North Eastern Pacific Ocean, and a typhoon occurs in the North Western Pacific Ocean; while in the south Pacific or Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.
  7. 7. TROPICAL STORMS (CYCLONES) Tropical storms are given different names in different parts of the world.
  8. 8. TROPICAL STORMS AS HAZARDS A tropical storm is a hazard that brings heavy rainfall, strong winds and other related hazards such as mudslides and floods. Tropical storms usually form between approximately 5° and 30° latitude and move westward due to easterly winds. The Coriolis force sends them spinning towards the poles. In most areas, tropical storms are given names. The names are alphabetical and alternate between male and female. This makes storms easier to identify, especially when they are close together. It is hard to predict the path of a tropical storm, and therefore difficult to manage an adequate evacuation of an area if needed.
  9. 9. CORIOLIS FORCE Apparent force, due to the spinning of the Earth, which deflects movement of particles and wind.
  10. 10. HOW DO TROPICAL STORMS FORM? Hurricanes need a lot of heat to form, which is why they usually occur over tropical seas (at least 26°C). The sun is close to the equator, providing energy to heat the ocean. The warm ocean heats the air above it causing it to rise rapidly. Water evaporates quickly from the hot surface of the ocean, so the rising air contains great amounts of water vapour. The rising air starts to spin (clockwise in the northern hemisphere). The centre of the storm - the eye - is calm. As the air rises it cools, condenses and forms towering cumulonimbus clouds. The rapidly rising air creates an area of intense low pressure. The low pressure sucks in air, causing very strong winds. Once the storm moves over land it starts to lose energy and fades.
  12. 12. GENERAL KNOWLEDGE Tropical storms bring intense rainfall and very high winds, which may in turn cause storm surges and coastal flooding, and other hazards such as flooding and mudslides. They develop as intense low-pressure systems over tropical oceans. Winds spiral rapidly around a calm central area known as the eye. The diameter of the whole tropical storm may be as much as 800km, although the very strong winds that cause most of the damage are found in a narrower belt up to 300km wide.
  13. 13. GENERAL KNOWLEDGE In a mature tropical storm pressure may fall to as low as 880 millibars. This, and the strong contrast in pressure between the eye and outer part of the tropical storm, lead to very strong winds of over 118km/h.
  14. 14. CONDITIONS NEEDED For tropical storms to form, a number of conditions are needed: - Sea temperatures must be over 27 C to a depth of 60m (warm water gives off large quantities of heat when it is condensed – this is the heat which drives the tropical storm). - The low-pressure area has to be far enough away from the equator so that the Coriolis force (the force caused by the rotation of the Earth) creates sufficient rotation in the rising air mass.
  16. 16. TROPICAL STORM Tropical storms is a generic term that includes Hurricanes (North Atlantic), Cyclones (Indian Ocean and the Bay of Bengal), and Typhoons (Japan). A tropical storm is a low pressure system up to 600km in diameter with wind speeds of up to 300km/h (typically 160km/h) and bringing up to 30-50cm of rainfall.
  18. 18. TROPICAL STORM There is no need to learn all of the details of the Saffir-Simpson scale (measuring the scale of tropical storm strength and impacts), but it is good to know about the lower, middle and upper ends of the scale. Category 1: winds 119-153km/h, storm surge generally 1.2-1.5m above normal. Category 3: winds 119-209km/h, storm surge generally 2.7-3.6m above normal. Category 5: winds greater than 249km/h, storm surge greater than 5.5m above normal.
  19. 19. TROPICAL STORM MANAGEMENT The unpredictability of tropical storm paths makes the effective management of tropical storms difficult, while the strongest storms do not always cause the greatest damage.
  20. 20. TRACKING TROPICAL STORMS Information regarding tropical storms is received from a number of sources including: - Satellite images - Aircraft that fly into the eye of the tropical storm to record weather information - Weather stations at ground level - Radars that monitor areas of intense rainfall
  21. 21. PREPARING FOR TROPICAL STORMS There are a number of ways in which national governments and agencies can help prepare for a tropical storms. These include risk assessment, land-use control (including floodplain management) and reducing the vulnerability of structures and organisations.
  22. 22. LAND USE ZONING The aim is to control land use so that the most important facilities are placed in the least vulnerable areas, including floodplains.
  23. 23. REDUCING STRUCTURES’ VULNERABILITY New buildings should be designed to be wind and water resistant. Communication and utility lines should be located away from the coastal area or installed underground. Improvement of building sites includes raising the ground level to protect against flooding and storm surges. Protective river embankments, levees and coastal dykes should be regularly inspected for breaches due to erosion. Improved vegetation cover helps to reduce the impact of soil erosion and landslides, and facilitates the absorption of rainfall to reduce flooding.
  25. 25. QUESTION Why is managing tropical storms difficult? 5 minutes test.
  26. 26. ANSWER Managing hurricane impact is difficult. The unpredictability of tropical storm path makes the effective management of tropical storms difficult. The strongest storms do not always cause the greatest damage. People living in coastal areas face increased risks associated with tropical storms.
  27. 27. WHAT TO DO BEFORE A TROPICAL STORM Know where your emergency shelters are. Have disaster supplies on hand. Protect your windows. Permanent shutters are the best protection. A lower-cost approach is to put up plywood panels. Trim back branches from trees. Trim branches away from your home and cut out all the dead or weak branches on any trees on your property. Check your home and car insurance. Make arrangements for pets and livestock. Develop an emergency communication plan.
  28. 28. EMERGENCY SHELTERS AUCKLAND CENTRAL ASB Stadium, Kohimaramara Rd, Kohimaramara (adjacent to Selwyn College) City Impact Church, 385 Mt Wellington highway, Sylvia Park Eden Park, Reimers Ave, Mt Eden Ellerslie Events Centre, 80 - 100 Ascot Ave, Ellerslie Ellerslie War Memorial Hall, 138 Main Highway, Ellerslie Fickling Centre, 1011 Mt Eden Rd, Three Kings Freemans Bay Community Hall, 52 Hepburn St, Freemans Bay Victory Church, 98 Beaumont St, Freemans Bay Glen Innes Hall, 102 Line Rd, Glen Innes Mt Albert Senior Citizens Hall, Corner Wairere Ave and New North Rd, Mt Albert Mt Albert War Memorial Hall, corner Wairere Ave and New North Rd, Mt Albert Onehunga Community Centre, 83 Church St, Onehunga Panmure Community Hall, 7-13 Pilkington Rd, Panmure Te Huruhi Primary School, 7 Donald Bruce Rd, Waiheke Waiheke High school, 1 Donald Bruce Rd, Surfdale
  29. 29. WHAT TO DO DURING A TROPICAL STORM Listen to the radio or television for tropical storm progress reports. Check emergency supplies. Make sure your car is full of fuel. Bring in outdoor objects such as lawn furniture, toys, garden tools, and anchor objects that cannot be brought inside. Secure buildings by closing and boarding up windows. Remove outside antennas and satellite dishes.
  30. 30. WHAT TO DO AFTER A TROPICAL STORM Assist in search and rescue. Seek medical attention for persons injured. Clean up debris and effect temporary repairs. Report damage to utilities. Watch out for secondary hazards: fire, flooding, etc.
  31. 31. TORNADOES Tornadoes are small and short- lived but highly destructive storms. Because of their severe nature and small size, little is known about them. Tornados consists of elongated funnels of cloud that descend from the base of a well-developed cumulonimbus cloud, eventually making contact with the ground beneath.
  33. 33. TORNADOES Some students think that hurricanes and tornadoes are the same – they are very different in origin, scale, impact and potential for management.
  34. 34. TORNADOES
  35. 35. WHAT IS A TORNADO? A tornado is a violent, destructive weather system, with powerful rotating winds (up to 300km/h). Tornadoes are intense, low- pressure systems, and their development depends on instability in the atmosphere, convergence and strong updrafts in the air.
  36. 36. FAVOURED AREAS Many tornadoes have a short life. They can last from several seconds to more than an hour. Favoured areas are temperate continental interiors in spring and early summer, when insolation is strong and the air may be unstable, although many parts of the world can be affected by tornado outbreaks at some time or another. The Great Plains of the USA, including Oklahoma, Texas and Kansas, have a high global frequency, and are particularly prone at times when cool, dry air from the Rockies overlies warm, most “Gulf” air.
  37. 37. TORNADO DAMAGE About 1000 tornadoes hit the USA each year. On average, tornadoes kill about 60 people per year, mostly resulting from flying of falling (crushing) debris. There are 3 damaging factors at work: - The winds are strong so objects are removed or damaged - Rotational movement tends to twist objects from their fixings - Low atmospheric pressure near the vortex centre is a major source of damage
  38. 38. FUJITA TORNADO DAMAGE SCALE The Fujita scale relates the degree of damage to the intensity of the wind. It should be used with caution as it does not take into account differences in building structure and materials. CATEGORY F0 Light damage (more than 117km/h) Damage to chimneys, branches broken off trees, sign boards damaged CATEGORY F3 Severe damage (254-332km/h) Roofs and walls torn off well-constructed houses, trains overturned, cars lifted off CATEGORY F5 Incredible damage (419-512km/h) Strong-frame houses lifted off foundations and swept away, cars flying around 100m
  39. 39. MANAGING TORNADOES As yet there is no effective way of managing tornadoes. The best advice is to stay indoor and, if possible, underground. There is no proof that cloud seeding can or cannot change tornado potential in a thunderstorm.
  41. 41. QUESTION To what extent it is possible to manage the risk of tornado damage?
  42. 42. ANSWER As yet there is no effective way of managing tornadoes. The best advice is to stay indoors and, if possible, underground. There is no proof that cloud seeding can or cannot change tornado potential in a thunderstorm. CLOUD SEEDING Cloud seeding is a form of weather modification, a way of changing the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud.
  44. 44. CLOUD SEEDING – 1950’s NZ TRIALS Over twenty countries around the world are actively involved in weather modification trials. New Zealand is not one of them. According to NIWA, "So far we do not know enough about clouds and how to seed them, to be sure of the effects. We might make less rain when we want more, or more hail when we want less. So cloud seeding is not done in New Zealand". Trials were carried out in the 1950s using planes to drop dry ice in the clouds to bring rain to dry farms. The trial was unsuccessful.
  45. 45. This image explaining cloud seeding shows the chemical either silver iodide or dry ice being dumped onto the cloud, which then becomes a rain shower. The process shown in the upper-right is what is happening in the cloud and the process of condensation to the introduced chemicals.
  46. 46. CLOUD SEEDING – 1970’s NZ TRIALS Back in the 1860s trials were conducted where cannons were used to shoot clouds in the hopes it would alter rainfall. In the 1970s the New Zealand Government dropped silver iodide from planes over Marlborough in the hopes they could create rain to ease droughts. But if the air is dry and there are no clouds then there is no point in seeding. It makes about as much sense as planting plant seeds on top of concrete instead of in the soil.
  48. 48. HURRICANE KATRINA Hurricane Katrina was a devastating storm that hit the area around New Orleans, USA, on 25 August 2005. It had social, economic and environmental impacts.
  49. 49. KATRINA’S SOCIAL IMPACTS 1,800 people died. 300,000 homes were destroyed. 3 million people were left with no electricity. People had to move out of the area.
  50. 50. KATRINA’S ECONOMIC IMPACTS $300 billion of damage. Oil platforms were destroyed. Shops were looted. Fuel prices rose. Tourism decreased.
  51. 51. KATRINA’S ENVIRONMENTAL IMPACTS The storm surge flooded large areas of the coast. 80% of New Orleans flooded as man-made levees, overwhelmed by extra water, broke. Cotton and sugar cane crops were destroyed. Delicate coastal habitats were destroyed. Tornadoes were created.