Cyclones - a natural hazard & Disaster
What is a natural hazard and a natural disaster?
A natural disaster is any occurrence that is the result of any natural hazard, such as dry leaf litter is a hazard, and a disaster such as a bushfire is the result of the leaves. A natural disaster also includes any area that has been affected by that natural hazard, such as a burnt forest. Natural disasters and natural hazards are sometimes vital for the continuation of a sustainable environment. Some plants require disasters, such as bush fires to germinate seeds, which then continue the trees survival. Other things such as long droughts can be solved through natural disasters, aided by floods.
For tropical cyclones to form, certain environmental conditions must be present. These include:
- A warm ocean surface, above 26 degrees Celsius, and very human air. This means that they will usually only occur between 5 and 30 degrees on both sides of the equators.
- It also requires unstable atmospheric conditions, which is a characteristic of low-pressure systems.
When the hot air rises, cooler air rushes in to fill the area left vacant by the hot air. The Coriolis effect of the Earth spinning on its axis causes the air to spiral upwards with considerable force. This in turn causes the winds to rotate faster, causing the tropical low to deepen in intensity into a tropical depression, and eventually a cyclone which is anywhere between hundreds of kilometres to thousands of kilometres wide.
Cyclones are also characterised by strong winds, yet in their centre is a clear, calm region called the 'eye'. When the cyclone continues its course, and the winds return from the other direction, they may seem to be more violent. The winds are not just rotating; there is also the effect of the warmer air continually rising and cold air rushing in. That is why the winds are so strong, and seem to move in all directions.
Winds gusts in a category 5 cyclone can exceed 280 kph, and a fully developed cyclone pumps out about two million tonnes of air per second, making it a very dangerous hazard which is very hard to avoid once it is in full swing. This makes cyclones one of the most dangerous natural disasters that affects Australia.
- A warm ocean surface, above 26 degrees Celsius, and very human air. This means that they will usually only occur between 5 and 30 degrees on both sides of the equators.
- It also requires unstable atmospheric conditions, which is a characteristic of low-pressure systems.
When the hot air rises, cooler air rushes in to fill the area left vacant by the hot air. The Coriolis effect of the Earth spinning on its axis causes the air to spiral upwards with considerable force. This in turn causes the winds to rotate faster, causing the tropical low to deepen in intensity into a tropical depression, and eventually a cyclone which is anywhere between hundreds of kilometres to thousands of kilometres wide.
Cyclones are also characterised by strong winds, yet in their centre is a clear, calm region called the 'eye'. When the cyclone continues its course, and the winds return from the other direction, they may seem to be more violent. The winds are not just rotating; there is also the effect of the warmer air continually rising and cold air rushing in. That is why the winds are so strong, and seem to move in all directions.
Winds gusts in a category 5 cyclone can exceed 280 kph, and a fully developed cyclone pumps out about two million tonnes of air per second, making it a very dangerous hazard which is very hard to avoid once it is in full swing. This makes cyclones one of the most dangerous natural disasters that affects Australia.