- Created by: Charlotte Herondale
- Created on: 04-01-18 11:28
Pressure & the Coriolis Effect
Solar energy creates air movement. Warm air rising = low pressure. Cool air sinking = high pressure.
Low pressure causes cyclones. High pressure causes anticyclones.
Low pressure in the centre of a storm tries to get to the higher pressure air and is deflected so spins.
High pressure air sinks and moves outwards. Low pressure air rises and ground winds move towards it.
In an attempt to equalise pressure, wind moves from high to low pressure areas.
The Coriolis Effect is when wind curves from its original trajectory due to the spin of the Earth. Points on the equator spin faster because the equator has to spin faster than the poles to get its full width round 360 in the same time as the smaller poles.
North = curve right
South = curve left
Global Circulation Systems
Cold air sinking = no clouds = dry environment = low millibars.
Warm air rising = clouds = wet environment = high millibars.
Below the Equator are the Southeast trade winds, which go from SE to NW. This is a Hadley cell.
Above the Equator are the Northeast trade winds, which go from NE to SW. This is a Hadley cell.
Below the Tropic of Capricorn are the Westerlies, which go from NW to SE. This is a Ferrel cell.
Above the Tropic of Cancer are the Easterlies, which go from SE to NW. This is a Ferrel cell.
Below the Sub-Polar Low are the Polar Easterlies, which go from SE to NW. This is a Polar cell.
Above the Northern Sub-Polar Low are the Polar Westerlies, which go from NW to SE. This is a Polar Cell.
Climate Change & Tropical Storms
Milankovich Cycles: Changes in the Earth's orbit, fluctuating over millenia and changing the heat Earth recieves from the sun depending on our distance away.
Hotspots: Hot areas on the sun's surface which, when aligned with Earth, warm the planet more than usual.
How Climate Change Affects Tropical Storms: INTENSITYWHEN/WHEREUNCERTIANITY
- Warmer oceans breed a larger amount of more violent storms
- Thermal expansion causes sea levels to rise, causing larger storm surges and making flooding easier
- Air holds more moisture, meaning more rainfall and flooding caused by storms or other weather systems
Oceans will be warmer all the time and create more energetic storms
Hotter oceans mean storms will be less limited in range and happen more often as it will always be warm.
Random weather patterns and constant high temperatures will make storms unpredictable
Formation of Tropical Storms
I) The sun warms up the oceans.
II) Water temperatures reach 27 degrees C.
III) Moist air rises, creating a low-pressure eye.
IV) Air cools as it rises, causing condensation into rainclouds.
V) Cool air sinks to create the eyewall.
VI) As air circulates in an effort to equalise pressure, winds form.
VII) The storm moves but is made to spin due to the Coriolis Effect.
The eye, up to 50km across, has descending air + low pressure. Wind is light and it is hot; no rain/clouds.
The eyewall has spiralling, rising air + high pressure. Wind is strong and it is cold; lots of heavy rain.
Between the edges and the eyewall, pressure falls. Winds are heavy and there is lots of hevy rain still.
At the edges of the storm, there are some clouds. There's less wind, clouds & rain + higher temperatures.
Hurricane Severity Scale
Category I: 74-95mph sustained winds; low level of damage
Category II: 96-110mph sustained winds; moderate level of damage
Category III: 111-130mph sustained winds; extensive level of damage
Category IV: 131-155mph sustained winds; extreme level of damage
Category V: 155+mph sustained winds; catastrophic level of damage
LDCs can be hit harder by a low-level hurricane than an MDC faced with a high-level hurricane as they have worse infrastructure; less resources; and often high disease rates and/or overpopulation.
UK Extreme Weather
Extreme cold weather is an extreme and/or unseasonal bout of very cold weather, often coming with snow. eg: Winds and snow in the NE, December 2010
The UK is under threat from storms, with lots of rain, high winds and large waves on the coast caused by winds over seas/oceans. eg: Storm Stella, 2017
A drought is when there is a prolonged peiod of no rain or other precipitation. This causes a shortage of water and crops, as they are unable to grow. eg: UK-wide drought, 2010-12
Flooding occurs when there is a lot of rain or other precipitaion in a short period of time, and this build upon the ground or in rivers, which then overflow. eg: Carlisle Floods, 2015
Causes of St. Jude's Day Storm, 2013
- Depression formation: a cold front of northern air undercut warm southern air, causing a pressure difference at full occlusion
- Powerful jetstream: strong winds 5-7 miles up in the atmosphere at a lower-than-usual latitude travelling from west (USA) to east (UK).
St Jude's Day Mini Case Study
Environmental:10 million trees destroyed; power cabes fell; large waves on coast
Economic: Building damages insurance; economy losses; disrupted travel to work
Social:4 people killed; homes had no electricity; lack of communication
Prediction: 5 days' warning; MET computer accurately predicte path; warnings issued for different areas
Protection: Trees felled so they couldn't be blown over; isurance companies recruited extra staff for the expected amount of claims
Planning: Warnings meant people could plan their activities around the dangers and disruptions caused by the storm
Warnings: Yellow - severe weather possible/could affect you; Amber - largeish likelihood of severe weather affecting you; Red - extreme weather is expected
Distribution of Tropical Storms
Tropical storms form between the Tropic of Cancer (23.5° north) and the Tropic of Capricorn (23.5° south) and most are 5-30° north or south of the equator, as the sea temperatures are above 27°C, which is required for the formation of tropical storms.
Areas affected include Central America, Africa, South Asia and Indonesia, as they are in the path of this area close to the equator.