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The Challenge of Natural Hazards - Weather Hazards - Coggle Diagram
The Challenge of Natural Hazards - Weather Hazards
Formation of Tropical Storms
Development of Tropical Storms
Tropical storms develop between 5 and 30 degrees north and south of the equator, when:
Sea temperature is 27 degrees Celsius or higher
Winds shear between the higher and lower parts of the atmosphere is low
The warm surface water evaporates, rises and condenses into clouds. This releases huge amounts of energy, producing powerful storms. The rising air creates an area of low pressure, which increases surface winds. Low winds shear prevents clouds breaking up as they rise, so the storm stays intact
Easterly winds near the equator move tropical storms towards the west
The storms spin because of the Coriolis effect
As the storm moves over the ocean, the energy from the warm water strengthens the storm, so wind speeds increase. Storms lose strength when they move over land or cooler water, because the energy supply from the warm water is cut off
The majority of storms occur in the northern hemisphere from August to October, while in the southern hemisphere most storms occur from December to April
Features and structure of a Tropical Storm
CGP diagram page 10
Climate Change
Climate Change:
The large-scale, long term shift in the planet's weather patterns or average temperature
Global Warming:
A gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide
Quaternity Period:
The current geological period dating from 2.6 million years ago. We live in the Holocene Epoch dating from 12,000 years ago (since the last ice age)
Effects of Climate Change on Tropical Storms
Frequency
Oceans will stay at 27 degree Celsius for longer each year so there's a longer period where tropical storms can form. This may lead to more tropical storms
Distribution
As the average ocean temperature rises more of the world's oceans could be above 27 degrees Celsius. This may lead to tropical storms forming in areas that haven't experienced them before
Intensity
Higher sea surface temperatures are likely to result in more evaporation and increased cloud formation so more energy is released. This could mean storm become more powerful
Managing Climate Change
Mitigation
Planting Trees
Increases the amount of CO2 that is absorbed from the atmosphere through photosynthesis
Alternative Energy Production
Replacing fossil fuels with nuclear or renewable energy to reduce greenhouse gas emissions
In the UK more offshore wind farms are being built and several tidal and wave projects have been planned
International Agreements
The 2015 Paris agreement aims to reduce greenhouse gas emissions and limit global warming. It has been signed by 195 parties
Each country has submitted a pledge which indicates how much they will try to reduce their carbon dioxide emissions by. The EU and the UK pledged to reduce emissions by 40% by 2030
Carbon Capture
CCS is designed to reduce emissions from power stations burning fossil fuels
CCS involves capturing CO2 and transporting it to a safe place where it can be stored e.g. deep underground
Adaption
Managing Water Supply
Dry areas are predicted to get drier leading to more water shortages so people need to use resources more efficiently
Rainwater and wastewater can be collected and recycled
Changing Agricultural Systems
It may be necessary to change crop types that are more suited to the new climate conditions
In some regions, biotechnology is being used to create new crop types which are more resistant to extreme weather events
Coping with Rising Sea Levels
At current rates sea levels are predicted to rise 65cm by 2100 flooding many coastal areas
Better flood warning systems are being put in place and physical defences such as flood barriers are being built e.g. The Thames Barrier, London
Adaption is the process of adjusting to the current and future effects of climate change
Mitigation means making the impacts of climate change less severe by preventing or reducing the emission of greenhouse gases into the atmosphere
Evidence for Climate Change
Ice and Sediment Cores
Ice sheets are made up of layers of ice, one layer per year
By analysing the gases trapped in the layers of ice scientists can tell what the temperature was that year
Tree Rings
As a tree grows it forms a new ring each year, the tree rings are thicker in warm wet conditions
Scientists take cores and count the number of rings and measure the thickness to see what the climate was like
Can measure the past 10,000 years
Temperature Records
Since the 1850's global temperatures have been measured using thermometers. This gives a reliable but short-term record of temperature change
Case study: Typhoon Haiyan
Facts
Typhoon Haiyan made landfall in the Philippines on 8th November 2013
Tacloban and Cebu were among the worst affected areas, with up to 280 mm of rain and winds reaching a maximum of 314 km/hour
A storm surge with waves of up to 2.3 m combined with a high tide, meant that Tacloban was hit by waves of up to 5 m
Effects
Primary
8000 people were killed
Over 1 million homes were severely damaged or destroyed
1.9 million people were made homeless
Strong winds damaged electricity lines, and water supplies were contaminated by salt water from the storm surge
The heavy rain and storm surges flooded 600,000 hectares of farmland
The cost of damage was estimated at approximately US $13 million
Secondary
Flooding triggered several landslides, which blocked roads and delayed the arrival of aid
5.6 million workers lost their jobs after businesses and agricultural land were destroyed
The lack of clean water caused outbreaks of diseases such as dysentery
Responses
Immediate
PAGASA broadcasted warnings about Typhoon Haiyan two days before it made landfall. This led to the evacuation of 800,000 residents before the storm. Unfortunately, some of these people died when evacuation centres flooded
Fisherman were warned not to go to sea
The Philippines declared a state of emergency, which led to many charities offering aid in the form of flood, shelter and clean water
Plan International constructed pit latrines for 100,000 people to help prevent the spread of disease
Long-Term
The UN appealed for over $300 million to help fund rebuilding and relief
Charities built new storm-resident houses for those who lost their homes
The Philippines' tourism board encouraged people to visit the country after the storm by emphasising that most areas were unaffected and that money from tourism would help with the rebuilding process
Global Atmospheric Circulation
High and Low Pressure Belts
Global atmospheric circulation is the transfer of heat from the equator to the poles by the movement of air
Air moves due to differences in air pressure - winds blow from high pressure areas to low pressure areas
The global atmospheric circulation system is divided into loops called cells - each cell has warm rising air that creates a low pressure belt and cool sinking air that creates a high pressure belt
Each hemisphere has three cells. Here's how air moves in these cells:
The sun warms the Earth at the equator, causing the air to rise. This creates a low pressure belt
As the air rises it cools and moves away from the equator
30 degrees north and south of the equator, the cool air sinks, creating a high pressure belt
At the ground surface, the cool air moves either back to the equator (as trade winds) or towards the poles (as westerlies). These winds curve because of the Earth's rotation - this is the Coriolis effect
60 degrees north and south of the equator the warmer surface winds meet colder air from the poles. The warmer air rises, creating low pressure
Some of the air moves back towards the equator, and the rest moves towards the poles
At the poles the cool air sinks, creating high pressure. The high pressure air is then drawn back towards the equator
Effect on Weather
At the equator, the sun is directly overhead - this means the Earth's surface receives a lot of solar radiation, so it's hot. Warm, moist air rises and forms clouds, so it rains a lot
By the time air reaches 30 degrees north and south of the equator, it has released most of its moisture as rain. The dry air means there are few clouds and little rainfall, so deserts are often found at this latitude
The UK lies close to the low pressure zone at 60 degrees north. Warm rising air brings lots of cloud cover and rainfall, often as low pressure systems carried from the Atlantic by westerly winds
UK Weather Hazards
Strong Winds:
Strong winds can damage properties and disrupt transport
Uprooted trees and debris can injure or kill people
Heavy Rainfall:
Too much rain can cause flooding, which can damage homes, disrupt transport networks and drown people
Recovering from flooding can cost millions of pounds
Snow and Ice:
Snow and ice can cause injuries due to slipping and deaths due to the cold
Schools and businesses can be forced to shut, and disruption to travel can have economic impacts
Drought:
Water supplies can run low, causing economic impacts such as crop failures
Rules to conserve water have to be introduced
Thunderstorms:
Heavy rain, strong winds and lightning can all occur during thunderstorms
Lightning can cause fires, which can damage property and the environment, and can occasionally kill people
Heat Waves:
During long periods of hot weather, pollution builds up in the air. This can cause heat exhaustion or breathing difficulties, which can kill people
Disruption to transport from rails buckling or roads melting can cause economic impacts - but the tourism industry may benefit from the better weather
Case Study: St Jude Storm
27th and 28th October 2013
10 million trees lost
99mph winds
4 deaths
£0.5 billion damage
Winds enhanced by sting jet
Met office predictions accurate
Disruption to power and communcation