Topic 1a - Climate and Tropical Cyclones Flashcards
Where is heat from solar radiation the most intense?
Near the equator
Which causes a difference in air pressure?
The difference in temperature causes changes in air pressure. Air travels from high to low pressure.
Describe the Hadley Cells?
- 0- 30
- Sun warms it up and the heat causes hot air to rise
- this cools, condenses and forms clouds = rain = low pressure
- cool dry air moves 30 N&S of the equator
Describe the Ferrel Cells?
- 30-60
- air sinks and causes there to be high pressure = cloudless skies and very little rainfall
- cool air reaches the ground surface as moves as surface winds (trade winds or westerlies) towards the equator or the pole
What are trade winds?
They move towards the equator
- blow from SE to NE –> meet at the equator and are heated by the sun
- rise to form clouds
What are westerlies?
Wind that moves towards the poles
- from NW to SW
Describe Polar Cells?
- 60-90
- Warmer surface winds meet colder parts from the poles and as warm air is less dense it rises = Low Pa and frontal rain
- At the poles, (90 N and S) cool air sinks and high pressure is creates and wind is drawn towards the equator as surface winds
How is heat transferred around the world?
Due to winds and ocean currents
What are surface currents?
- caused by winds
- help wind away from the Equator and bring warm water from the Caribbean
What are deep ocean currents?
- driven by water density
- water freezing at the poles so the surrounding water gets saltier and denser
What is thermohaline circulation?
- denser water sinks causing warmer water to flow to the surface
- warmer water is then cooled and sinks creating a cycle = Thermohaline circulation
Describe the climate zones:
- arid (dry) between H and F cells (high Pa) = low rainfall and high temp
- tropical - between H cells (low Pa = high rainfall and temp)
- polar - between P cells (high Pa) = low temp and low rainfall
What is the quarternary period?
Last 2.6 million years ago
- glacial(colder) and interglacial(warmer) periods within in
What are the possible natural causes of climate change?
- Milankovitch cycles
- Volcanic activity
- Solar output
- Asteroid collisions
How do the Milankovitch cycles influence climate change?
- eccentricity = orbit of earth changes from circular to elliptical (every 96,000 yrs)
- axis tilt - the tilt of Earth is closer or further from Sun = normally 23* and effects solar radiation and thus causes glacial and interglacial periods 41,000 yrs)
- precession - axis of earth wobbles like a spinning top (every 22,000 yrs)
How does Volcanic activity influence climate change?
- volcanoes eject material (ash) into the atmosphere
- this reflects the Sun’s rays to space so the surface cools and causes short term changes
How does Solar output influence climate change?
- solar output changes in short cycles of 11 years or a longer cycle of several hundred years
- when it’s reduced = cooling
- e.g in Maunder Minimum = low solar activity between 1645 and 1715
How do Asteroid collisions influence climate change?
- they throw dust into the atmosphere and decreases the amount of energy of the Sun reaching the earth
- decreases the global temperature
- e.g Younger Dras around 12,000 years ago
What are the natural pieces of evidence of climate change?
- Tree rings - more wet and warm = thicker rings/yr
- Ice cores - drill into ice sheets of ice and analyse gases (CO2) trapped in layers of ice to tell temp (more O2 = less heat)
- Historical records = diaries and paintings (harvest or Thames fair)
When were the Medival warm period and Little ice age?
- 900 to 1300 = more harvest of grapes
- 17th cent = Londo frost fairs, Inuit sightings and arctic ice reaching to Scotland
What is the natural greenhouse effect?
- it warms the Earth
- energy from the sun (short wave radiation) is reflected into space as longwave radiation
- gases (CH4, CO2, water vapour) = act as an insulating layer and let short wavelength in and trap some longwave radiation (rest is lost in space as heat)
What human activities cause an enhanced greenhouse effect?
- caused by human activities
- farming, energy, industry and transport
How does farming cause an enhanced greenhouse effect?
- cows release methane when they fart
- rice paddies are flooded fields = release methane
- fewer trees so less CO2 absorbed
How does energy cause an enhanced greenhouse effect?
- CO2 when burning fossil fuels such as oil, natural gas and coal
How does the industry cause an enhanced greenhouse effect?
- cement production releases co2
- industrial waste in landfills release CH4 when decaying
How does transport cause an enhanced greenhouse effect?
- use fossil fuels so more cars used meaning more congestion thus more engines running for longer
What is the evidence of human activity causes climate change?
- Less artic ice
- global temp rising
- rising sea level and warming oceans
- extreme weather
How are less ice and rising temp evidence of human activity causes climate change?
- Less artic ice = decreased by more than 3% each decade over last 35 yrs
- global temp rising - rise 1* since 1880 and expected to rise 3-4* by 2100 and top 10 warmest temp recorded have been all after 2000
How are extreme weather and rising sea level of human activity causes climate change?
- rising sea level and warming oceans - increased by 0.2m = eustatic sea level rise as ice on land melts not other sea and thermal expansion caused as water expands as it gets warmer
- extreme weather = more frequent in 2010 and 2014 had broken most rainfall records in the UK
How does climate change impact people?
- more death due to heat and less death due to cold
- land may be too hot or cold to inhabit
- low lying coastal flooding = migration = overcrowding
- globally fewer crops as smaller due to heat but high latitude counties benefit in warmer conditions
- less crop yield = malnutrition, ll health and death (esp in equator)
- more extreme weather = more money for prediction, reduction impact and rebuilding after
Why is there uncertainty about future climate change?
- emissions = don’t know how they will change as pop increases, more economic dev and the quantity of both
- complexity - don’t know what climate changes will happen = we don’t understand a lot of natural processes
- management - don’t know what attempts are made to change greenhouse emissions and how successful they are
What is needed for tropical cyclones to develop?
- develop over warm water
- sea temp is 26.5 or higher, wind shear and lower parts of the atmosphere
- source is 5-30 N and S
Why don’t cyclones form further than 30 N and S?
- not enough energy for them to form as the water isn’t warm enough
How do tropical cyclones develop?
- warm moist air rises condense and release powerful energy
- rising air has low Pa so increases surface winds
- rotation of the earth deflects the wind path as the cyclone spins
- moves towards the west due to easterly winds near the equator and move further away
- path curves to the east near mid- latitude westerlies
- cyclones intensity due to energy from warm water
When do cyclones from in Northern or Southern Hemisphere?
The sea temperature is highest in the
- Northern Hemisphere in June- Nov
- Southern Hemisphere in Nov - April
When do cyclones gain intensity?
- due to energy from the warm water
Why do cyclones dissipate?
- due to loss of energy as they move towards land or cold water
- change in windspeed cause also cause dissipation
How does climate change affect sea temp?
- more temp = more cyclones
- triggers conditions as warm moist air increases to 26.5*, sea where ocean water is warmest, winds converge at the ocean surface causing air to rise
- formation away from the equator so Coriolis effect will cause storm to rotate and have low wind shear
Whats are ITCZ?
- Inter-tropical convergence zones
- areas of permanent low pressure which form as part of H cells near the equator
- cause more thunderstorms as have prevailing wind and warm conditions (lots of cyclones sourced here)
Describe the structure of a cylone:
- above cyclone = dense canopy of cirrus clouds (caused by uplift of warm, moist air) - last 7-14 days
- swirling around centre = rain bands - clouds that can stretch for 100km = heavy rain and strong winds
- centre - eye and around - eyewall = thick band of cloud rising 15km (strongest wind and heaviest rain and low temp)
- eye has no rain and clear skies = air fall back (H.Pa)
- edge of cyclone has low wind speed, smaller clouds, less intense rain and high temp
Which way do cyclones spin in each hemisphere?
- N - anti-clockwise
- S - clockwise
How do tropical cyclones lead to storm surges?
- more sea levels = stronger wind
What are the physical hazards associated with tropical cyclones?
- high winds
- intense flooding
- storm surges
- coastal flooding
- landslides
How do high winds due to tropical cyclones have an impact?
- can kill people by flying debris
- uproots trees and flows them over
- destroys homes
How do intense flooding due to tropical cyclones have an impact?
- heavier near the eye
- flooding property = unemployment as businesses destroyed
- pollutes freshwater environment with saltwater
How do storm surges due to tropical cyclones have an impact?
- caused by a rise in sea levels due to low Pa and high winds
- drowns people in strong currents
- erodes coastal habitats
- contaminates farmland
- damages coastal habitats (coral reefs)
- damages crops and livestock killed
How do coastal flooding due to tropical cyclones have an impact?
- due to storm surges and strong winds driving large waves onto the shore
- electric supplies cut off
- sewage overflows
- lack of sanitation - diseases
- chem waste spilt
How do landslides due to tropical cyclones have an impact?
- heavy rain = unstable hills as a high level of rain saturates the soil = heavy and more vulnerable if rock underneath is impermeable
- damages roads and makes it hard for rescues to happen (vehicles can’t get through)
- deposits sediment in lakes and rivers killing fish and other wildlife
How can the impact of a tropical cyclone be assessed?
- Saffir Simpson Hurricane Wind scale
- assesses wind speed and likely damage to property
- over category 3 - potential to cause massive damage
- 1 weakest with 120-150km/hr
- 5 = strongest with over 250km/hr
What are the physical vulnerabilities of tropical cyclones?
- low lying coastal areas = more vun. to storm surges as large waves
- low relief areas - more likely storm surge
- high relief - more likely landslides
- some areas are in the cyclone path
- thus island nations are the most vulnerable
What are the economic vulnerabilities of tropical cyclones?
- more dev - more accurate weather prediction
- coastal defences, evacuation procedures, disaster response teams, more food supplies
- less dev = dependent on agriculture so may not have insurance
- more dev = larger economic impact due to roads, cars, buildings
What are the social vulnerabilities of tropical cyclones?
- poverty or deprived areas have worse quality buildings, looting, bad healthcare, little money for teams, hard to rescue people due to poor infrastructure
What are the ways of preparing for cyclones?
- atm Pa measuring (need to be made locally tho) - buoys in oceans or fly planes for accurate readings
- satellite tracking - register large banks of precipitation and find eye (expensive to install)
- modelling - comp models calculated path, landfall, intensification and dissipation
- communication
How can communication mitigate the impacts of tropical cyclones?
- gov activated defences (flood barriers)
- emergency shelter and evacuation points of higher ground
- broadcast on TV and media
- house on stilts so safer from floodwater
What should the response for cyclones be?
- rescue teams search for trapped people
- providing food/water
- providing medical care and shelter for victims
- rapid reconstruction and repair of the affected area e.g repair of power/drinking water/ clearing roads
