Weather hazards Flashcards
What is the global atmospheric circulation?
The movement of air across the globe in specific patterns.
How does the global atmospheric circulation influence our biomes?
It creates winds across the planet and leads to areas of high rainfall e.g. tropical rainforests, and areas of dry air e.g. deserts.
What happens in the Hadley Cell?
Ground at equator intensely heated by sun. Causes air to rise = low pressure zone. Air rises, condenses and forms thick storm clouds. Air continues to rise to upper atmosphere.
Where does the Ferrel Cell occur?
Between 30° and 60° north of the equator, and between 30° and 60° south of the equator.
What happens in the Ferrel Cell?
Air on the surface is pulled towards the poles, forming winds. Winds pick up moisture as they travel over oceans. At 60°N&S, winds meet cold air from poles. Where the two air masses meet, there are unstable weather conditions e.g. wet, windy weather in UK.
What happens in the Polar Cell?
At the poles, air is cooled and sinks towards the ground = high pressure. Then flows towards lower latitudes (60°N&S). Cold polar air mixes with warmer tropical air and rises upwards = low pressure and unstable weather.
Why is weather hot and wet at the equator?
Hadley Cell causes air to rise at the equator = low pressure = lots of cloud formation = rainfall. Sun’s rays have to travel through less atmosphere to reach equator (than poles) so heat is more intense.
Why is weather cloudy and wet in the UK?
Located at 55-60°N, at boundary of Ferrel Cell and Polar Cell. Warm air mass meets cold air mass = low pressure & unstable weather conditions.
Why is weather hot and dry in the desert?
Deserts found approximately 30°N&S. Air here is sinking (at top of Hadley Cell) = high pressure = very little air rising = very little condensation = very little rainfall.
What is a tropical storm?
A natural hazard that brings heavy rainfall, strong winds and other related hazards e.g. mudslides and floods.
What are the different names given to tropical storms?
Hurricanes, typhoons and cyclones.
What are the conditions required for tropical storm formation?
Warm oceans – 27°C or above. Spin created by the Coriolis Effect. Unstable, rapidly rising air. Little wind shear (light winds blowing high up in the atmosphere).
How are tropical storms structured?
Eye of storm – centre of storm; high pressure = no clouds; calm conditions. Eye wall – either side of eye; low pressure = unstable conditions and rising air = severe wind, rain, thunder, lightning. Either side of eye wall – smaller thunderstorms, strong winds and heavy rain.
How are tropical storms formed?
Water vapour evaporates from warm ocean surface. Evaporated air rises, cools, condenses = forms towering thunderstorm clouds. As air condenses, heat is released, powering storm and drawing more warm ocean water, creating more thunderstorms. Thunderstorms join together to form giant spinning storm. Officially a tropical storm when winds 75mph. Storm develops eye at centre. Air descends rapidly here = high. Tropical storm carried across ocean by prevailing winds, gathering strength from ocean. pressure = calm conditions.
Why do tropical storms weaken when they reach land?
Energy supply (warm ocean water) is cut off and because there is friction with the land.
How is hurricane strength measured?
Using the Saffir-Simpson Scale.