Weather Hazards Flashcards
(43 cards)
How does the way the atmosphere circulate affect the Earth? Why?
It impacts global weather and climate patterns because the movement of the air around the globe is influences the temperature and humidity.
What is atmospheric circulation?
Within the Earth’s atmosphere, the air is constantly moving in different directions because of the sun’s energy, differences in pressure, and the rotation of our Earth. These movements cause the air to circulate around the Earth, following generally predictable movements.
What are the three distinct patterns of air circulation?
Circular air movements called cells:
1) The Hadley cell: at the equator - hot, moist air rises - moves to higher latitudes (30°) and sinks (to 0° - a.k.a the equator)
2) The Ferrell cell: at around 60° either side of the equator - moist air rises and travels to lower latitudes at around 30° where it sinks, along with air travelling from the equator
3) The Polar cell: at 60° North or South of the equator - moist air rises and travels to the poles (90°) where it sinks
How is wind created?
When air particles move. Air particles will always move from an area of high pressure to an area of low pressure
What is the Coriolis affect? How does this affect wind?
Wind is deflected in different directions due to the Earth spinning, so the winds end up travelling in a curved direction. This spinning effect is known as the Coriolis effect so the winds deflected right are in the Northern Hemisphere and winds deflected left are in the Southern Hemisphere.
What happens when warm, moist air rises?
It creates an area of low pressure and creates cloudy and wet conditions.
What happens when cold air rises?
It creates an area of high pressure and creates dry conditions.
Where are low pressure belts?
- At the equator
- 60° either side of the equator
Where are high pressure belts?
- 30° either side of the equator
- At the poles
What do pressure belts and surface winds impact?
- Temperature
- Humidity
What is the climate like at the equator?
Humid and very rainy due to the hot, moist air rising than condensing to form rain clouds.
What is the climate like at the subtropics?
It is very dry due to dry air sinking forming areas of high pressure - in the day it is extremely hot but at night it is very cold due to no clouds being able to retain the heat.
What is the climate like at the subpolar latitudes?
It is cloudy and wet due to the low pressure belt however it is not as warm due to the sun shining less directly there than it does at the equator.
What is tropical storm?
It is very large and is formed in the tropic. They usually affect small islands and coastal regions.
What are the characteristics of tropical storms?
They have high winds and torrential rain.
What is a tropical storm called in different regions?
- Hurricane - USA, Latin America/The Caribbean
- Cyclone - Australia (Oceania), Madagascar
- Typhoon - India, Japan, the Philippines
What are the conditions needed for tropical storms to form?
1) Ocean temperatures around 26° - 27° - this allows the storm to gain energy
2) A depth at least 50 km
3) Unstable air pressure - usually where high pressure and low pressure meet
4) The wind shear must have a swirling motion for the tropical storm to form but it cannot be too strong or the storm system will be ripped apart in early stages
5) It will form 5°-30° around the equator to have the ‘Coriolis Effect’
What is the tropical storm formation?
1) Warm, moist air rises leaving an area of low pressure below - this causes warm air from the surroundings to move into this low pressure area and rise too. Overall, warm air is constantly rising and accumulating in the atmosphere.
2) When the warm air rises, it eventually cools - this moist air will then condense and form large thunderstorm clouds
3) The whole system is spinning due to the Coriolis Effect. In the southern hemisphere, the storm spins clockwise and in the northern it spins anticlockwise
4) The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds. At 75mph the storm can classed as a category 1 tropical storm
5) The storm develops an eye in the centre. This is an area of extremely low pressure (can be 15% lower pressure than areas outside the storm) where cool, dry air descends. The weather within the eye is relatively calm and cloud free.
What surrounds the eye of the storm?
The eyewall - the most intense and powerful area of the storm. Warm, moist air rapidly rises here, with extremely high winds, thunder and lightning, and torrential rain. In very intense storms, sustained winds can reach up to 150mph and gusts can exceed 200mph.
What happens when a storm reaches landfall?
The low pressure and high winds will cause a large amount of sea water to be pushed onto the coast, which is called a storm surge. When the storm reaches land, it no longer has a supply of energy and the eye eventually collapses and the storm dissipates. Heavy rain can persist for days.
What is distribution?
Where the tropical storms are formed and where they move to.
How is climate change affecting tropical storms?
- Since sea surface temperatures are rising where tropical storms are not usually active, tropical storms could potentially form in these areas in the future.
- In addition, with sea surface temperatures rising, the locations that typically develop tropical storms may expand to other regions.
- Scientists are further researching how the patterns of tropical storms are being affected.
- However, at the moment, studies show that climate change has not increased the frequency of tropical storms and that there has been no significant increase in regions that experience tropical storms.
- Some studies show that there may have even been a decrease.
- On the other hand, there is significant evidence that the intensity of tropical storms has been increasing due to climate change.
- Likely in the future, the number of Category 4 & 5 tropical storms will increase and wind speeds will increase by 10%
What is an example of climate change affecting tropical storms?
In 2004, Hurricane Catarina hit the South-East coast of Brazil, which had never been struck by a tropical storm before. Sea surface temperatures were higher than average meaning a storm was able to form in the South Atlantic.
What is frequency?
The number of tropical storms.
