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Weather Hazards (3.1-3.9)
What is global atmospheric circulation?
Global atmospheric circulation refers to the large-scale movement of air across the Earth, driven by solar energy, which distributes heat and moisture. It includes patterns like the trade winds, westerlies, and polar easterlies, influencing climate and weather systems worldwide.
High pressure is…
caused by sinking air.
Low pressure is…
caused by rising air.
What do surface winds do?
They transfer heat and moisture from one area to another and they move from high to low pressure.
Why do surface winds curve?
They curve because of the Earth’s rotation.
Why do surface winds change seasonally?
They change as the tilt and rotation of the Earth causes relative changes in the position of the overhead sun.
What are the three interconnected circular air movements called?
Hadley cell, Ferrel cell and Polar cell.
Why is the UK cloudy and wet?
It is cloudy and wet because 60° north is close to where the polar air from the north meets warm subtropical air from the south. The surface winds from the SW usually bring warm and wet weather because rising air cools and condenses forming clouds and rain.
Why are deserts hot and dry?
They are hot and dry because most deserts are found about 30° N and S of the equator where sinking air is found in between the Hadley and Ferrel cells. This means there is high pressure, little rain, hot daytime temperatures and very cold nights.
Why, at the equator, is it hot and sweaty?
It is humid at the equator because there is lots of low pressure meaning when mixing with the suns rays directly overhead, the hot humid air rises, cools and condenses, causing heavy rain - hence the tropical rainforests.
What are other names for tropical storms?
They are named differently in different parts of the world e.g. hurricanes, cyclones and typhoons.
Where do tropical storms form and when? What conditions does it need to form?
They form 5-15° N and S of the equator , in summer and autumn, where:
ocean temperatures are the highest (above 27°C)
the spinning (Coriolis) effect on the Earth’s rotation is very high
intense heat and humidity makes the air unstable
What triggers tropical storms to form? How do they grow? How do they weaken?
The trigger is the upward movement of evaporated air and moisture which cools and condenses to form towering thunderstorm clouds. The condensing air releases heat, powering the storm and drawing up more water. Multiple thunderstorms join together to form a giant rotating storm. Coriolis forces spin the storm at over 75mph creating a vast cloud spiral with a calm eye of rapidly descending air. Prevailing winds drift the storm over the ocean gathering strength as it picks up more energy. On reaching the land the energy supply (evaporated water) is cut off and the storm will weaken.
What is the structure of a tropical storm?
What evidence is there that global warming has impacted natural systems, including the distribution, frequency and intensity of tropical storms?
over the last few decades sea surface temperatures in the tropics have increased by 0.25-0.5°C
in the North Atlantic, 6 of the 10 last most active years since 1950 have happened since the 1990s
in the North Atlantic, hurricane intensity has risen in the last 20 years
What evidence is there that global warming may impact natural systems, including the distribution, frequency and intensity of tropical storms?
in the future, tropical storms may extend into the South Atlantic and parts of the sub-tropics
in the future, tropical storms may become more powerful
True or False: There is currently clear evidence that the numbers or intensities are increasing.
False.
There is currently no clear evidence that the numbers or intensities are increasing. More data will be needed over a longer period of time.
What is the case study for tropical storms, where did it take place and when did it happen?
‘Super’ Typhoon Haiyan, the Philippines and November 2013.
What are three basic facts about Typhoon Haiyan?
it is one of the strongest category 5 storms ever recorded
very low air pressure pressure caused 5m storm surge swept on shore by winds up to 275km/h (170mph)
Coastal devastation included 90% of Tacloban destroyed by storm surge
What are primary effects?
They are the initial impact of a natural event on people and property, caused directly by it.
What were the primary effects/impacts of strong winds, heavy rain and storm surge from Typhoon Haiyan?
6300 killed - most in the storm surge
over 600,000 displaced
40,000 homes destroyed or damaged
wind damage to buildings, power lines and crops
over 400mm of rain caused widespread flooding
What are secondary effects?
They are the after-effects that occur as indirect impacts of a natural event, sometimes on a longer timetable.
What were the secondary effects/longer-term impacts resulting from the primary effects from Typhoon Haiyan?
14 million affected including 6 million jobs lost
flooding caused landslides - blocking roads and restricting access for aid workers
shortages of power, water, food and shelter, leading to outbreaks of disease
infrastructure including schools destroyed
looting and violence in Tacloban
What is an immediate response?
It is the reaction of people as the disaster happens and in the immediate aftermath.
What immediate responses were there to Typhoon Haiyan?
rapid overseas aid including NGOs
US helicopters assisted search and rescue, and delivery of aid
field hospitals helped injured
over 1200 evacuation centres set up
What is an long-term response?
It is the later reactions that occur in the weeks, months and years after the disaster.
What long-term responses was there to Typhoon Haiyan?
UN and international financial aid, supplies and medical support
rebuilding of infrastructure
rice farming and fishing quickly re-established
homes rebuilt in safer areas
more cyclone shelters built
How can you reduce the effects of tropical storms?
By monitoring, predicting and protecting.
What can you do to monitor and predict tropical storms?
Developments in technology includes satellite tracking. These allow prediction maps showing the track of tropical storms to be created.
How can you protect yourself against a tropical storm?
Methods of protection usually involve anticipating the design of buildings - everything from reinforced walls and roofs, window shutters, storm drains and sea walls.
How can you use planning to reduce the effects of tropical cyclones?
‘Preparedness’ is all about contingency planning for the inevitable. Mostly it means education and media campaigns raising individual and community awareness so that people understand the dangers and can respond apropriately.
What is the difference between weather and climate?
Weather describes the day-to-day conditions of the atmosphere, e.g. temperature or rain. Climate describes the average weather over a 30-year period.
Why is the UK described as having a ‘roundabout’ location when talking about its climate and weather?
Despite its moderate climate, the UK does experience weather hazards - occasionally extreme weather events linked to its location at the meeting point of different points of weather from different directions.
What is the case study for severe weather in the UK, where did it take place and when did it happen?
The Somerset Levels floods, 2014.
The Somerset Levels area an extensive area of low-lying land in south-west England and has a long history with flooding.
What caused the Somerset Levels floods?
a sequence of south-westerly depressions brought record rainfall in January and February.
high tides and storm surges swept water up the rivers from the Bristol Channel preventing normal flow.
rivers clogged with sediment had not been dredged for 20 years.
What social, economic and environmental impacts were there for the Somerset Levels floods?
over 600 houses flooded
villages cut off - disrupting work, schools and shopping
estimated £10 million damage
16 farms evacuated, 140 km2 of farmland flooded and 1000 livestock evacuated
power supply, roads and railways cut off
floodwaters contaminated with sewage, oil and chemicals
massive debris clearance required
What immediate responses were there to the Somerset Levels floods?
huge media interest was generated
cut-off villagers used boats for transport
community groups and volunteers gave invaluable support
What long-term responses were there to the Somerset Levels floods?
£20 million Flood Action Plan launched by Somerset County Council and Environment Agency to reduce further risk
8km of two rivers dredged
road levels raised
vulnerable communities will have flood defences
river banks raised and strengthened, more pumping stations built
possible tidal barrage at Bridgewater by 2024
True or False: The UK has experienced an increase in the number of extreme weather events in recent years.
True.
Why might extreme weather events be on the increase?
Trend over many years may be linked could be linked to global warming, which:
leads to more energy in the atmosphere, which could lead to more intense storms
possibly affects atmospheric circulation, bring floods to generally drier areas and vice versa.
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