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1. Earth’s Energy Budget and Regional Temperature Variations
Earth’s energy budget
 Global energy balance: between insolation and long-wave terrestrial radiation
o Scattering: gases and dust particles can redirect solar radiation: short waves
scattered more, that’s why we see blue sky
o Reflection: short-wave radiation returned to space as outflow
 Dependent on albedo: greatest variability over water
o Absorption: take in solar energy – thermal excitation – internal molecular
motion – increase in temperature – short-wave radiation becomes long-wave
radiation to warm up atmosphere
 Oxygen absorbs short-wave, ozone absorbs long-wave
o Greenhouse effect
 Earth transparent to short-wave radiation but absorptive of longwave radiation
 Carbon dioxide and water vapour aids process by absorbing and reemitting radiation – passed between gases – warm up atmosphere
 Poleward heat transfer
o 2.4x more solar energy received at equator than at poles
o Latitudinal differences
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o Latitudinal balance
Regional temperature variations
 Proximity to sea
o Moderating effect of oceans due to high specific heat capacity (5x land’s):
need more energy to heat up / cool down – take longer to do so than land
o Solar energy can penetrate great depths and distribute energy over wider
area
o Tides and currents
 Ocean currents
o Gulf Stream and North Atlantic drift transport heat to keep British Isle winter
mild
o Labrador current keeps North-Eastern America cool in summer
 Altitude
o Every 1000m ascent, temperature falls by 10 degree Celsius
o Air at surface denser, has more dust particles to trap heat
 Cloud cover
o Tropical vs. desert region’s diurnal temperature
o Clouds keep radiation from coming in and going out
 Aspect: equator vs. pole-facing slopes
2. Atmospheric / Oceanic Circulations and the Occurrence of Seasons
Global atmospheric circulation
 Forces affecting air movement
o Pressure gradient force
 Greater pressure, higher wind speed
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Pressure difference due to denser air (more pressure) vs. less dense
air (less pressure), unequal heating of earth
o Coriolis force
 Deflects pressure gradient force due to rotating effect of Earth
 Stronger at poles than at equator
 Affects wind direction, affected by wind speed
o Friction: present at surface but absent for flow aloft
o Geostrophic winds: parallel flows to isobars with velocities proportional to
pressure gradient force
o Surface winds
 Wind speed drops due to friction – pressure gradient force not
affected but Coriolis force affected – pressure gradient force stronger
so wind direction changes – wind moves at an angle across isobars
towards low pressure area
The major wind belts
o Hadley cells and trade winds
 Get deserts 30N and 30S due to descending air – compression of
rising air – adiabatic heating – relative humidity falls – cannot reach
dew point – no rain
 Equator-ward wind from horse latitudes called trade winds
 Trade winds converge at ITCZ which shifts more over continents than
water bodies due to varying heat capacities
o Ferrel cells and westerlies
 Westerly on average, disrupted by migration of cyclones
 Due to Coriolis force
o Polar cells and easterlies
 Subsidence
 Where it meets warmer mid-latitude flow – polar front
Subtropical highs (comparison)
o Briefly explain land / water specific heat capacity and compare N/S
o How ITCZ shifts and why it shifts that way
o Subtropical variations
Monsoon circulation: due to migration of ITCZ across equator
Global oceanic circulation (1/4 of earth’s heat transport)
 When atmosphere and water in contact, energy passed to water through friction
 Drag exerted by winds cause water surface to move
Seasonal climatic variations
 Revolution and tilt at 23.5 to the perpendicular – solstices and equinoxes
 Daylight hours determined by circle of illumination
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3. Upper Atmosphere Wind and Jet Streams
Origin of jet streams
 Great temperature contrasts at surface produce great pressure differences aloft –
increase wind speed due to pressure gradient force
Polar jet stream
 Changes speed and location with seasonal contrasts
 Meanders
Weather
 Cyclones
o Due to ridges and troughs as jet stream meanders across Earth, locations at
lower latitudes may experience colder temperature than those of higher
latitudes
o Moves north, drags air from below and speeds up – low pressure region at
surface due to rising air – surrounding air will move in an anticlockwise
direction
o Speed and path of jet stream affects intensity of cyclone
o Eg. 1987 UK big hurricane because it was in the path of jet stream
 Droughts due to persistence of high pressure in an area
 Can have short term cyclonic variations as cyclone redistributes heat – originally
higher latitudes cooler but it becomes warmer
4. Precipitation Formation
Conditions
 Saturation: air cooled below dew point / holds sufficient water
 Condensation nuclei, without which relative humidity must be >100% to produce
clouds
Environmental lapse rate: rate at which temperature decreases with height (about
6.5C/km)
Atmospheric stability / instability
 Dependent on intensity of surface heating – impact on DALR / SALR
 Stable if DALR / SALR faster than ELR – air cannot rise
 Unstable if DALR / SALR slower than ELR – air can rise
 Conditional instability if DALR slower but SALR faster than ELR or vice versa
 Determined by whether air parcel can rise through surrounding air
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Air lifting mechanisms
 Convective lifting due to instability of air
o Caused by strong surface heating due to surface irregularities (eg. dark vs.
light surface)
o But clouds formed at this height (condensation height) limited because of
instability because surface heating only lasts for first few km
 Orographic lifting
o Windward: adiabatic cooling from lots of clouds
o Leeward: adiabatic heating and already released precipitation
o Formation of rain shadow desert eg. Patagonia desert in Argentina
6. Adverse Weather Conditions – Tropical Cyclones
Formation
 27C ocean, sufficient twist
 Warm sea heats air above – low pressure area formed – wind rushes and spirals in –
releases heat and moisture before descending
 Rising air cools producing cumulonimbus clouds – cloud tops carried outwards
 Self-sustaining heat energy created: large amounts of energy transferred as warm
water evaporates – release of latent heat as it rains – more wind rushing in to low
pressure area
Characteristics
 5 - 20
 June to December in northern hemisphere, Jan to March in southern hemisphere
 Moves westwards initially due to easterly trade winds, but as storm intensity
increases it moves polewards (influenced by mid-latitude westerlies to move
eastwards)
 Eye (highest pressure)
 Eye wall: sudden drop in pressure, rapidness results in extreme weather conditions.
Velocity increases because near the core due to conservation of angular momentum
Dissipation
 Cannot support large-scale flow aloft
 No warm water body
 Hits land: more chilled than sea, increase surface roughness – friction – distorts air
flow and decreases wind speed – eye fills with clouds
Impacts
 Storm surge: 90% of deaths
o Piling up of water as wind drags surface waters forward
o Low pressure: every millibar drop, sea level increases by 1 cm
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o Eg. Bangladesh <2m above sea level
Wind damage
o Affects greater area than storm surge
o Eg. Hurricane Andrew US$20b
Inland freshwater flooding
o Affect the greatest area due to heavy rains
o Eg. Hurricane Agnes US$2b even though Category 1
Management
 Prediction
o Satellites: but due to remote sensing can still estimate wind speeds / position
rather inaccurately
o Aircraft reconnaissance
o Radar
 Mitigation
o Early warning systems: need lead time but must prevent from over-warning
because costly and lost of credibility
o But due to population increase, need earlier warning systems
 Evacuation and first aid strategies
7. Past Climate Change
Evidences
 Glacier evidence
o Erosion: transform V-shaped valleys into U-shaped valleys; striae: polish
exposed rocks to smooth finish
o Deposition: tillites have very wide assortment – poorly sorted deposits
 Sediment evidence
o Type and number of forams
o Oxygen-isotope analysis: 18O / 16O ratio higher indicates glacial extension
 Ice core evidence
o Microscopic air bubbles trapped as fresh snow is laid
o More carbon dioxide, higher temperature
o More dust, chemical composition of aerosols with high acidities – volcanic
activity
 Pollen analysis
o Type and number of species through radio carbon dating because vegetation
communities can have its spores blown by wind and buried in bogs
o But not every pollen can be identified to species level
o But not all species produce the same number of pollen
 Scots pine large quantities, but beech small quantities and usually
under-represented
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Tree ring analysis
o Thicker – more favourable temperature / moisture
Causes (talking about Northern hemisphere)
 Eccentricity (shape of orbit)
o Now Earth 3% closer to sun on Jan 4 than on July 4 – 6% more solar energy
received in Jan than in July
o When very eccentric, 23% - 30% more solar energy
o Winter warmer: temperature increase, can hold more moisture, more
precipitation and summer cooler: less snow melt – glacier extension
 Obliquity: angle of tilt
o Currently at 23.5 but can change between 22.1 to 24.5 - affects seasonal
contrast
 Precession of equinoxes
o Now tilted towards North Star but may switch to Star Vega – winter when
Earth furthest from sun and summer when Earth nearer to sun – greater
seasonal contrast
 Solar variability
o Sun spots: magnetic storms on sun’s surface that extend deep into interior
o Associated with increase solar output
o Corresponds to Little Ice Age but not to other locations’ climates
 Volcanic activity
o Release of aerosols into stratosphere that can remain for years
o Increase albedo over area
o Increase cloud albedo because aerosols act as condensation nuclei making
clouds denser
o Eg. 1815 eruption of Mt Tambora, Indonesia – year without summer
 Plate tectonics
o Slow movement only accounts for temperature changes over great span of
geologic time
8. Climate of the Cities
Urban heat island effect
 Differences within a localized area greatest in winter, late evenings / night,
considering minimum temperature eg. in London, Kew had 70 more frost free days
than nearby rural Wisley
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Causes
o Changes in thermal capacity
 Buildings able to store more heat and release more in the night
compared to shallow layers of soil
o Sensible and latent heat transfer
 Urbanization results in water being drained out quickly – surplus
energy goes to increase temperature rather than evaporation
o The urban structure
 Lower albedo than natural surface
 Some insolation absorbed and some scattered as diffuse radiation –
strikes another surface and process repeats
 Heat trapped within due to multiple reflection
o Combustion: eg. Manhattan – winter 2.5x solar energy vs. summer 5x
o Presence of pollutants – greenhouse effect
o Wind speed
 Frictional drag decreases wind speed but if regional winds are strong
enough, urban heat island cannot be detected
 Areas above and between buildings more gusty
Urban induced precipitation
 Causes
o Thermally induced upward air motions – atmospheric instability
o Condensation nuclei due to pollutants – condensation at relative humidity
78%
o Rougher surface impedes progression of weather systems – clouds may
linger over city longer and generate more precipitation
 Eg. Paris higher rainfall on weekdays (especially Thurs and Fri when dust particles
accumulate)
 Suburbs more rainy on weekends when pollutants float there
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Other changes
 Reduction in solar radiation: greater albedo and low angle of sun passes through
more pollutants
 Lower relative humidity: high temperature and less moisture
 Country breeze: wind blowing in from surroundings and upward air movement in
cities
9. The Enhanced Greenhouse Effect and Global Warming
Greenhouse gases
 Carbon dioxide
o Burning of fossil fuels: 90% northern hemisphere
o Deforestation: less photosynthesis and release of stored carbon dioxide in
plants
 Methane: rice paddy cultivation and digestive processes of ruminants like cattle
 Other trace gases: nitrus oxide and chlorofluorocarbons
Positive feedback mechanisms
 Carbon dioxide – higher temperature – more evaporation – more water vapour in air
– higher temperature
 Higher temperature – melting ice caps: reflective surface replaced by more
absorptive surface of water body – higher temperature
Negative feedback mechanisms
 More moisture – more clouds – more insolation reflected – lower temperature
o But melting ice caps effect greater
 Increase temperature of sea – more marine organisms – take in carbon dioxide
through photosynthesis – when die buried in great depths of ocean and remove
carbon dioxide from atmosphere – lower temperature
o But increase in temperature causes seas to store less carbon dioxide
Predicted future temperature
 Poles experience greater temperature contrast because atmosphere very stable –
heat trapped
 Global dimming reduced due to removal of sulfuric particles in atmosphere due to
environmental regulations
Consequences
 Sea level rise
o Thermal expansion, melting glaciers
o Coastal erosion and retreat of shoreline: extent dependent on the gradient of
the shoreline
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o Eg. Male in Maldives: 85% of island will be inundated by 1m increase in sea
level because it is only 1m above it
o Nile Delta: flooding of farmland - $32b of damage to Alexandria in terms of
tourist revenue, crops etc.
Agricultural productivity
o Increase in temperate regions which are wealthier due to increase in
precipitation – longer growing season but decrease in poorer regions 
leads to greater disparity between north and south
o Sea water creeps in – salinization – inundated farmland
Ecosystem
o Plant migration, coral bleaching – affects food chain and habitat of marine
creatures
o Problem is the rate of change too rapid and huge for organisms to adapt
Industries
o Freshwater for steam / cooling for refinery affected as seawater crept
upstream
o Forestry industry: need r+d to invent heat and drought-resistant crops
o Trans-Alaska pipeline to US may be damaged as permafrost melts
More extreme weather conditions happening more frequently: heat wave, droughts
Kyoto treaty
 Plant trees / change agricultural practices
 Earn / buy carbon credits
10. El Nino
El Nino Southern Oscillation (ENSO): seesaw pattern of atmospheric pressure between
eastern and western pacific
Walker circulation normally
 High pressure at eastern Pacific and low pressure at western Pacific
 Trade winds reinforced as the water travels westwards, resulting in western Pacific
having higher sea level (by 40cm) and a deeper thermocline (boundary separating
warm from cool water) as warm water is pushed there
 Convectional rain
 At Tahiti, Peruvian current – upwellings of cold ocean water makes thermocline
more shallow (40m)
 Air above flows from western Pacific to eastern Pacific as it rises due to convective
flows, reinforcing the movement
 Results in subsidence at Tahiti – deserts
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Walker circulation during El Nino reverse
 Flow from western Pacific to eastern Pacific: Kelvin waves weaken the influence of
trade winds
Prediction
 Once every 4 years, but becoming less predictable due to global warming
 Eg. usually 18 months but 1990 ENSO reached peak in early 1992, weakened
suddenly in mid 1992, and intensified in Nov 1992
Impacts
 Economic impact on Peru and Ecuador
o No upwelling of cold water – nutrients lost – fish population decimated – sea
birds don’t frequent – cannot harvest guano as fertilizer
o Abundance of rain inland supports pastures and cotton fields
 1982-83 El Nino
o Severe flooding in western Pacific: 350cm of precipitation when they
normally get 10-13cm per year
o Extreme storms in US
 1997 El Nino
o Severe droughts in Indonesia, but aggravated by deforestation
o Extreme storms in US and Hurricane Pauline in eastern Pacific
 Teleconnections: linkages of atmospheric and oceanic variables
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