Atmosphere Flashcards
How much would the sea level rise if the Greenland ice sheet melted
7m
Wipe out London, East Coast of USA, lots of Australian cities
When will the GRIS melt
Don’t know when could be 100 years could be 1000
How can we see how much CO2 was in the atmosphere 800,000 years ago
Ice cores - bubbles tell us about co2 content
What is the current co2 level in the atmosphere
400ppm (parts per million)
It was never above 200ppm and last year (2013) it rose to above 400 ppm
If we continue ‘business as usual’ what could the temp increase by by 2100
5C
What temp increase can the world handle
2C
What is the earths climate made up of
Ocean
Land
Land/sea ice
Chemistry
All interact
Where does energy in the earths system come from
The sun mainly
What is GRIS
Greenland ice sheet
How far from the earth is the sun?
approx. 150 million km
How hot is the sun?
15million C at the core, 6000K on the surface
what is the suns “atmosphere” called?
Corona
the Corona is much hotter than the surface but dues to its low density it radiates much less energy into space
learn
what do solar flares emit
they can emit large quantities of UV radiation and energised charged particles (magnetic storm)
what creates energy from the sun?
photons from the sun come down to earth creating energy - even artificial lighting is produced by the sun (coal, from dead plants, etc..) produced a long time ago.
what is the solar constant
the amount of energy given off from the sun
what happens in a solar maximum?
we are in a solar maximum currently.
there are more sunspots - more energy.
in about 5 years we will be in a solar minimum
what are sun spots?
cooler regions (ave. sunspot is 5 times the diameter of earth) area surrounding sunspots are hotter - sun is not constant. sunspot cycle is 11 years - peaks and troughs - Maunder minimum
what energy (electromagnetic spectrum) does the sun give off
produces viable a bit of ultraviolet and a small amount of infrared
what energy (electromagnetic spectrum) do humans and the earth give off
infrared
why are stars different colours
due to their heat
what is a unit of energy
joule
what is radiation
energy that travels
Planck’s law:
what is it
this describes the curve, every object with a temp above -237 C emits electromagnetic radiation
a “black body” is in the physical sciences a term for an idealised object that absorbs and emits electromagnetic radiation over all wave lengths.
Planck’s law describes the spectral distribution of emitted EM radiation of black body at a given temp.
sun and earth are apron like black bodies in terms of radioactive behaviour.
radiation laws: Stefan- Boltzmann law
explain
describes area under curve
Radiation laws: Wien’s displacement law
determines wavelength of the peak of the Planck distribution curve
how can you tell we have an atmosphere
the radiation of blue to red in a sunset etc…
what is an atmosphere
gravity helps to keep gases tight to earth.
our atmosphere reduces temp difference from the equator to the poles.
can’t hear anything if theres no air.
ozone in earths stratosphere gives UV protection.
what is the atmosphere of venus
venus is very warm because of greenhouse effect being thicker than it is on earth and CO2 is very high
describe the earths ‘first atmosphere’
existed 4.6-4bn years ago
when earth was a molten surface made up of h2, He, NH3 and CH4.
there were no oceans
no magnetic field (no poles) the magnetic field shields us from sun things
atmosphere was probably eroded by solar wind and cosmic rays
surface heat contributed to breakdowns of NH3 and CH4, freeing N and H
describe the earths ‘second atmosphere’
formed 4-3.3bn years ago
earth and cooled down and developed a solid crust but it was still very hot.
convective magma activity contributed to the formation of magnetic field capable of deflecting solar wind and cosmic rays.
volcanic activity with outgassing of H2O, CO2, NH3 and sulphates
atmosphere likely continued CO2, H2O , N2 and other volcanic gases, but still no oxygen (anoxic atmosphere)
how did oceans form?
once the temp cooled below 100C condensation of water vapour and precipitation became possible (3.8-3.9bn years ago)
oceans are a sink for CO2 (absorbed into water)
anaerobic bacteria began to develop in the deep ocean near volcanic hydrothermal vents
what was the oxygen catastrophe?
3.8-3.5bn years ago prokaryote cyanobacteria appeared as first oxygen producing organism(photosynthesis)
3.5bn year old stromatolites are found today in australia and southern africa.
they must have lived below 5m to be protected from harmful radiation but still within range of the sunlight
1.3bn years ago eukaryote cells were more efficient at producing oxygen.
1bn years ago the ocean was saturated with oxygen and O2 could subsequently accumulate in the atmosphere, eventually forming an ozone layer.
sisslved oceanic oxygen was toxic to anaerobic organisms (killed them off)
describe earths third atmosphere
development of more sophisticated forms of plant life led to increases in oxygen levels
co2 + h2o + sunlight = organic compounds +o2
anything more complex than bacteria could not have developed without the ozone layer due to all the UV
photodissociation of h2o played probably only a minor role o2 increase
present-day atmosphere (oxygen-nitrogen) formed approx 400 mya
formation of ozone layer and protection from harmful solar radiation were an essential requirement for he formation of plant life on land.
what is the vertical structure of the atmosphere?
atmospheric pressure is the consequence of the atmospheres own weight.
pressure is dependent on density, gravity and height
air is a compressible medium; therefore the density is not constant with height
in the global atmospheric pressure decreasing near-exponentially in vertical direction
90% of the atmospheric mass is below 10km
99.9% of the atmospheric mass is below 50km
atmospheric vertical profile: temperature
temp is the most often used criterion to subdivide the atmosphere into vertical layers with specific properties
temp is warmest closest to earth
earths temp is warmed from above and below
stratosphere gets warmer as you o up - ozone is here it warms up as it absorbs
thermodynamics
an ‘air parcel’ expands and cools when rising vertically.
conversely, air that descends is compressed and gets warmer.
the physical properties of air as a homogenous picture of gases are described by various thermodynamic laws.
alternative descriptions of vertical structure
layering by functionality
layering by composition
describe: layering by functionality
upper layer is the ionosphere (>50km), consists of ions (electronically charged atoms and molecules) created by solar UV radiation
layer below is the ozone layer (20-50km) sometimes also referred to as ozonosphere.
describe: layering by composition
homosphere (surface to about 80km) mixing ratio of oxygen to nitrogen, as well as long-lived trace gases constant. the hemisphere extends from sea level to the mesopause.
hetrosphere (above 80km) from this altitude molecular separation occurs due to gravitation with the heaviest molecules at the bottom and the lightest at the top.
what is the mean surface temperature, surface pressure, gravity acceleration on earth and venus
Earth: 280, 1, 9.81
Venus: 750, 90, 8.84
what type of molecule is water?
a dipole molecule, 1 oxygen 2 hydrogen. it is an efficient absorber of infrared radiation
what are the three phases of water on earth?
gas (vapour) - molecules move freely with other gases, compressible
Liquid - molecules move freely but constantly bumping and jostling, not compressible
Solid (ice) - molecules move slower, available to vibrate but not move freely.
what is latent heat transfer
as ice melts of water evaporates it absorbs heat and the surrounding environment cools in the process.
as water vapour condenses or liquid freezes to ice it releases heat to the surrounding environment.
the energy transferred is called latent heat. transition between gaseous and liquid phase involves about 7x as much heat energy as the other way round
describe stage 1 of evaporation at room temperature
at surface water molecules with sufficient speed (kinetic energy) will break away from surface and evaporate into air. With time amount of water in air increases as liquid water evaporates. condensation will also occur, however rate of condensation is smaller than the rate of evaporation.
describe stage 2 of evaporation at room temperature
Dynamic equilibrium (rates are equal) rate of condensation depends on the amount of water vapour in air. once air above water surface is saturated with water vapour, for every 1 water molecule that evaporates 1 condenses. at this stage amount of water vapour above surface will not increase further. if water vapour molecules are transported away by wind the saturation will not be reached and the evaporation rate will continue to exceed condensation (wind enhances evaporation)
what happens to liquid water molecules at higher temperatures
they have more kinetic energy (= higher average speed) and as a consequence the rate of evaporation will be higher
what will higher temp mean for the dynamic equilibrium
it will be reached at a higher concentration of water vapour above the water surface. for this reason cold air is dryer and warm air is more humid.
what does humidity describe?
the amount of water vapour in the air.
what is Dalton’s law of partial pressure?
states the total sum of sir pressure inside the parcel is equal to the sum of pressures of the individual gases.
what does vapour pressure describe?
the partial air pressure due to the water vapour contents in the air parcel.
what is saturation vapour pressure?
the vapour pressure at which the rate of evaporation is equal to the rate of condensation. it is a function of the air temperature.
what is relative humidity and how is it calculated?
the ration of the amount of water vapour actually in the air to the maximum amount of water vapour required for saturation at that particular temperature.
RH= water vapour content/water vapour capacity = actual vapour pressure/ saturation vapour pressure x100%
the relative humidity only tells us how close air is to being saturated with water not actual water vapour contents.
what is the dew point temperature?
represents the temperature to which air would have to be cooled for saturation to occur, warm dew points indicate moist air close to saturation whereas cold dew points indicate dry air.
why does relative humidity vary throughout the day?
mostly because of diurnal temperature variation (with rather unchanged amount of water vapour in the air at the same time)
what does the meridional variation of relative humidity show?
meridional (across latitudes)
shows highest values in moist-warm tropical regions and in the cold-high regions. low RH values can be found at 30N and S at the location of large deserts
what is fog and how does it form?
when condensation occurs near ground with viability reduced below 1km.
fog formation usually forms by cooling, by evaporating and mixing
what is Radiation fog?
cooling through night-time radiation and ground conduction
what is advection fog?
warm moist air mixes with cold dry air resulting in saturation
what is evaporation fog?
warm moist air mixes with cold dry air resulting in saturation
what is a cloud?
a visible aggregate of tiny water droplets or ice crystals suspended in the air.
what are the form major cloud groups
High clouds
middle clouds
low clouds
clouds with vertical development
what are the high clouds
Cirrus (wispy)
Cirrostratus (halo around sun)
Cirrocumulus (patchy, thin)
what are the middle clouds?
Altostratus (sun dimly visible)
Altocumulus (patchy, thicker)
what are the low clouds?
stratus (thin, smooth, fog like)
Stratocumulus (classic cloud but thinner)
Nimbostratus (big, smooth, steady precipitation)
what are clouds with vertical development?
cumulus (classic cloud) cumulonimbus (massive, showery precipitation)
Explain precipitation generation: rain droplets: formation by coalescence
occurs in liquid water clouds
problem that raindrops will only reach a certain size before becoming unstable.
Explain precipitation generation: rain droplets: Bergeron-Findeisen mechanism
responsible for majority of global precipitation, saturation vapour pressure over ice is lower than that over liquid water. leads to situation where there is net evaporation from liquid water droplets at the same tim as net deposition onto ice crystals. therefore in mixed clouds (water and ice) ice crystals and hailstones grow at the expense of water droplets, hailstones will grow until their weight overcomes cloud updrafts
what is the mean sea level pressure?
horizontal pressure variations are caused by changes in temp and air density.
as pressure varies with altitude, pressure values in synoptic surface charts need to be converted to their equivalent values at mean sea level
what are isobars
a pressure representation in charts, they describe the pressure distribution at the surface. regions with high pressure are ridges and low pressure are troughs
what is the pressure gradient force?
is directed from higher toward lower pressure at right angles to isobars. magnitude of force is directly related to the pressure gradients and a large PGF.
what forces are needed for air to move
pressure gradient force
coriolis force
centripetal forace
friction
what is the coriolis force?
describes an apparent force that is due tot he rotation of the earth. causes wind to deflect to the right of its intended path in the N.Hemisphere and left in the S. the force acts at right angles to the wind, thus only influencing wind direction not speed. the stronger the wind the greater the deflection. the force increases with latitude while being 0 at the equator.
what is geostrophic wind balance?
wind where the PGF and CF are in balance.
at high altitudes (no influence of friction from the ground) the PGF will result in wind motion until a speed is reached where PGF and coriolis force balance each other out.
what are the results of geostrophic winds?
circular motion (centripeal force) combo of PGF and Coriolis force results in centripetal force component which forces wind in circular motion. consequently with motion is anticlockwise around a low pressure system (cyclone) and clockwise around a high- pressure system (anticyclone) in the N.Hemisphere.
what is the planetary boundary layer (PBL)
between the surface and approx. 100m altitude the atmospheric flow is influenced by friction with the ground, this part of the atmosphere is the PBL.
what is the free troposphere?
the upper part of the troposphere, between the top of the PBL and tropopause, the wind here is not influenced by friction with the ground.
what is the effect of friction of the coriolis effect?
it reduces the wind speed which in turn reduces the coriolis force, no longer balance between CF and PGF, wind blows across isobars.
trade winds
- intense heating at the equator warms up air near the surface causing it to rise high into the atmosphere
- rising air creates a space and the equatorial low pressure zone, which sucks air from higher latitudes, forming the trade winds.
- this produces the trade winds which meet at the intertropical convergence zone (ITCZ)
atmospheric vs ocean heat transport
trouble with trade winds blowing towards ITCZ is that the climate system is desperately trying to export heat away from the equator, the in blowing winds do nothing to help this. in the tropics, its the surface currents of the oceans that transport most of the heat.
explain the hadley cell
- as the hot air that rose over the equator moves towards the poles, it slowly cools, due to its rise (adiabatic cooling) and its movement towards the poles (advective cooling)
- at about 30N and S it sinks forming the sub-tropical high pressure zone.
- the sinking air has lost most of its moisture and therefore dries out the land it sinks onto.
- some of this sinking air is pulled back towards the equator to complete the hadley cell.
global circulation: Westerlies
- some of the sinking air at 30N flows toward the poles and forms the Westerlies.
- it is from here that the atmosphere takes over as the main poleward transport of heat.
- the pollard movement of warm sub-tropical air only ceases once it meets the polar air mass at the polar front.
Explain the Ferrel cell and Polar cell
- intense cold at the poles causes the air to become super-chilled and sink, causing high pressure over the poles (polar high) and “blow-out” winds
- when this cold air mass meets the warmer westerlies at the polar front, moisture contained in the westerlies forced to condense and precipitate.
- it also forces the warm sub-tropical air to rise, as the cold polar air is much more dense
- this rising air completes the other two cells, ferrel cell and polar cell.
where does each cell occur?
Polar - at poles
Hadley - at equator
Ferrel - between the two
what are jet streams?
important component of all three cells, high altitude, fast flowing, narrow air currents
where do jet streams occur?
at the tropopause driven by the spin of the earth and strong differences in temperature. strongest is the polar jet, subtropical is slightly weaker. typically flow west to east.
what is an air mass?
extremely large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given altitude. depending on their origin and properties air masses are labelled either arctic, polar tropical or equatorial as well as maritime or continental.
what does local heating and cooling result in?
regional changes of air density.
dipping of the isobars results in horizontal pressure gradient force (?)
as air begins moving at altitude surface pressure begins to change and PGF results near surface with opposite wind direction.
local circulations brought on by changes in air temp are called thermal circulations
describe the sea and land breeze
its another type of thermal circulation
during day land heats up more quickly than sea and thermal circulation forms with a sea breeze
during night land cools down much faster and to lower temps than the sea, reversing the direction of the thermal circulation
temp difference during night is usually smaller such that land breeze is normally weaker than sea breeze
what impact does sea and land breeze have on circulation
on a clear relatively calm night, a weak country breeze carries pollutants from outskirts into city, where they concentrate and rise due to warmth of city’s urban heat island. this effect may produce a solution (or dust) dome from the suburbs to the centre of town
what is the urban heat island effect?
refers to significant increase in air temps in a metropolitan area in comparison to surrounding rural area.
what is the urban heat island a result of?
the interaction of the following factors:
- release (and reflection) of heat from industrial and domestic buildings
- absorption of heat by concrete, brick and tarmac during day, and its release into lower atmosphere at night
- enhanced cloud formation due to pollution can trap heat
- relative absence of water in urban areas means less energy is used for evapotranspiration and more is available to heat lower atmosphere.
- absence of strong winds to both disperse heat and bring cooler air from rural and suburban areas.
what is the mountain and valley breeze?
during day, sloped valley walls receive more insolation per surface area
air above valley walls gets heated more efficiently and gentle upslope wind, valley breeze, is formed.
during night cool (dense) air glides downhill into valley providing mountain breeze
daily cycle of wind flow is best developed in clear summer weather when prevailing winds are light.
at night cold air and pollutants drain downhill and settle in low-lying valleys
explain increased pollution caused by subsidence inversion
subsidence inversions form when air above a deep anticyclone (high pressure) slowly sinks (subsides) and warms due to compression.
colder air at surface is prevented from mixing with sinking warm air (its more dense than air above)
thick layer of polluted air is trapped in valley
top of polluted air marks base on subsidence inversion
what is the adiabatic process?
when an air parcel cools and warms, or expands and compresses, without exchange of matter and energy with the surrounding air.
what happens to air pressure and density with altitude?
they decrease
what happens as the air parcel rises? adiabatic process
its moved into area of lower surrounding pressure, molecules inside air parcel perform work to expand boundaries of parcel.
energy used for expansion must come from molecules inside air parcel.
reduction in kinetic energy results in lower temp
what happens when air parcel is moved to lower altitude with higher surrounding pressure?
surrounding air molecules compress boundaries of air parcel, increasing kinetic energy of molecules inside, air gets warmer.
what is the environmental lapse rate?
to do with the adiabatic process, its the rate at which the temp decreases with altitude
what is the principle concept of atmospheric stability?
refers to a condition of equilibrium with respect to vertical motion
air that is in a stable equilibrium will resist vertical motion
what happens in an unstable atmosphere?
unstable equilibrium means given a slight dislocation air will move farther away from its original position
what is the dry adiabatic lapse rate (DALR) ?
in unsaturated air (relative humidity is less than 100%) the rate of warming and cooling due to vertical motion remains constant.
rate of temperature change is approx. 10C for 1000m of change in elevation.
applies only to unsaturated air.
what is the moist adiabatic lapse rate (MALR)?
as rising air cools to its dew point temp the relative humidity reaches 100% and air becomes saturated.
further lifting of air parcel will result in condensation, a cloud forms, late heat is released inside air parcel.
as a result the cooling due to expansion gets partly off-set by the latent heat release.
this rate of temp change is on ave. 6C for 1000m of change in elevation.
only applies to saturated air.
what are the signs of a stable atmosphere?
veryical temp gradient (ELR) is smaller than then atmosphere is often absolutely stable
if air is forced to rise it will resist and spread horizontally.
moist/dry adiabatic rate per 1000m is more than the env lapse
what are the signs of an unstable atmosphere?
when vertical temp gradient (ELR) is large then the atmosphere is often absolutely or conditionally unstable
clouds grow vertically and plumes rise to great heights
moist/dry adiabatic rate per 1000m is less than the env lapse.
what is the influence of atmospheric stability?
major factor in transport of pollutants
- during afternoon when atmosphere is most unstable, pollutants rise, mix and disperse downwind
- at night when radiation inversion exists, pollutants from shorter stacks are trapped within the inversion, while pollutants from taller stacks above inversion are able to rise and disperse downwind.
what is the earths heat budget?
average annual incoming solar radiation exceeds the ave. annual outgoing infrared radiation, emitted by earth between 40N and 35S results in energy surplus at low latitudes and an energy deficit at high latitudes.
areas of heat gain and heat loss are equal and as such earths total heat budget is balanced.
describe the thermohaline circulation
warm water has lower density than cold water
water with higher salt content is heavier than fresher water
cold salty water is the heaviest
evaporation increases salinity in warm regions
during its journey to cold regions that salty water cools and sinks towards ocean floor, by contrast diffuse upwelling occurs in warm regions. therefore both temp and salinity gradients are the driver of an overturning circulation. MOC (meridional overturning circulation) is part of the global thermohaline circulation
red colours represent surface currents, blue represent deep currents
describe guld strema and north atlantic drift.
near US east coast
moves away from coast at Cape Hatteras
Speed of 10km/h
warm clear blue water contrasts with cooler darker more productive water to the north and west
clouds form over warm current as water vapour evaporates from surface.
describe meridional overturning circulation (MOC) atlantic
surface water becomes dense and sinks in north and south polar regions, being denser, antarctic bottom water slips beneath north atlantic deep water. water gradually rises across a very large area in tropical and temperate zones, then flows poleward to repeat cycle.
El Nino:
What is the importance of the pacific?
solar energy reaches pacific ocean and provides a large proportion of the heat needed to drive the global atmospheric circulation. the tropical pacific ocean at atmosphere represent a giant heat engine that converts solar energy into kinetic energy of the winds. small changes to atmosphere - ocean interaction in the pacific will have important consequences across the globe
what is the Walker circulation?
in normal conditions trade winds blow towards west across tropical pacific, resulting in pile up of warm surface water in west pacific. cold nutrient rich water wells up at S. American coast, supports diverse marine ecosystems, dry climate conditions. higher water temps results in extensive convection near Indonesia. this forms a convective loop, the walker circulation, which forms an important part of Hadley cell and general atmospheric circulation, reinforcing trade winds, results in formation of a zonal gradient in water temps.
what are El Nino conditions?
trade winds relax in central and western pacific.
thermocline in eastern pacific gets depressed, in western pacific its elevated. warm surface water moves eastward followed by rain, results in flooding in S.America (Peru) and drought in Indonesia and Australia. Eastward displacement of the heat source changes in atmospheric circulation occur affecting weather patterns in regions even at get distance from pacific
What are La Nina condition?
characterised by unusually cold sea surface temps. trade winds are stringer than usual. sometimes follow el nino event, opposite to el nino, impact tends to be opposite of el nino
human activities resulting in atmospheric CO2 increase
emissions from transport energy generation industrial and domestic heating cement production deforestation (land us change)
natural sources of atmospheric CO2
volcanoes - annual emission is 1/150th of anthropogenic sources
combustion processes e.g. forest fires
respiration of aerobic organisms (animals, humans)
how does ocean acidification occur?
uptake of increased CO2 reduces surface ocean pPH values - increase of acidity of ocean water.
increase is expected to affect:
coral reefs (declining calcification)
cold water corals
ecosystems where aragonite is essential (shell building)
temp increase results in coral bleaching
What is insolation - incoming solar radiation?
mostly at an oblique angle not vertical.
as a result same amount of radiative energy is being distributed over a larger surface area
on ave. the incoming solar radiation, distributed over whole surface of earth, equals to one quarter of the solar constant = 343 Wm-2
solar constant: 1370 Wm-2
what are the solar radiation pathways?
absorption
reflection
scattering
Transmission
describe absorption: solar radiation pathways
radiative energy converted to other forms of energy by gases or particles in the atmosphere.
describe reflection: solar radiation pathways
radiative energy is reflected back into space when hitting a surface
describe scattering : solar radiation pathways
radiative energy is (at least partly) redirected by air molecules and particles
describe transmission: solar radiation pathways
radiative energy passes through the atmosphere
how is incoming solar radiation scattered?
light that bounces off a surface at the same angle at which it strikes is reflected.
in the atmosphere, light from the sun is deflected in all kinds of directions (this is scattering)
clouds are made of water droplets that deflect light by geometric scattering, dark clouds = large droplets which absorb light
what are the different types of scattering?
depending on size they are distinguished between geometric, Mie and Rayleigh
Rayleigh scattering
air molecules result in rayleigh scattering. shorter (blue) wavelengths are scattered more efficient;y than the long (red) wavelengths. the longer the path length of the sunlight through air the more blue light is scattered and the sun and its immediate surrounding area appears red. the same effect results in the sky to appear blue, through rayleigh scattered diffuse light
what is the albedo
the % of radiation returning from a surface compared to that which strikes it, in other words its the ration between reflected radiation to incoming radiation. albedo of earth and its atmosphere is approx 30%
what are the modes of thermal energy transfer
conduction: through contact
convection: gases and fluids
radiation: world also in vacuum
describe the energy transfer in the troposphere
air in lower atmosphere is heated from ground upward, sunlight warms ground, and air above is warmed by conduction, convection and infrared radiation. further warming occurs during condensation as latent heat is given up to the air inside the cloud.
what is the greenhouse effect?
GHGs are atmospheric gases which absorb thermal radiation emitted by the earths surface. this blanketing effect leads to an increase in surface temps.
what are the GHGs?
water vapour is responsible for most of the greenhouse warming, but its atmospheric abundance is not changing directly as a consequence of human activities
CO2 concentration is the main “temperature controller” on earth.
CO2
Methane
Nitrous oxide
CFCs
Ozone
what is the zone where the trade winds converge called?
the inter-tropical convergence zone (ITCZ)
what is a monsoon climate?
monsoon refers to the reversal of mean surface wind direction from summer to winter.
most regions between 35N and 25S between 30 W and 170 E experience monsoon climates
caused by seasonal movements of ITCZ
what factors determine climate?
latitude: how much solar radiation Land and water: continuality ocean currents e.g. heat source prevailing winds - moisture advected (potential for rainfall) pressure cells - cloud coverage Mountain barriers altitude
what is weather?
is described through temp, pressure, rainfall, visibility and cloud coverage. its the current physical state of the atmosphere. measured in terms of variables that include temp, precipitation, cloudiness, humidity, air pressure, wind
what is climate?
described through long-term averages of weather conditions, and range of variability with respect to the mean value
what are the climate classifications?
Thornthwaite system: based on soil moisture content and evapotranspiration
Koppen system: most widely used
describe the Koppen system
based on temperature and precipitation, linked to vegetation. employs 5 major climatic types, A moist ave above 18C. B dry deficient precipitation. C moist mid latitude, mild winters, warm summers. D moist mid latitude server winters warm summers. E polar climates extremely cold
what is climate variability?
caused by natural changes in climate that all within the normal range of extremes for a particular region as measured by temp, precipitation and frequency of events
what is the north atlantic oscillation?
difference between sea level pressure between two stations during winter season
positive phase: stringer than usual pressure difference, fast storm tracks, warm wet winters in W.Europe mild and wet in E coast N.America
Negative phase: weak pressure difference, more cold air invasions on N.American E coast and Med Europe.
what does positive feedback lead to?
instability: changes in the system slow down
what does negative feedback lead to?
stability: change in the system slow down
explain the Milankovitch cycles
changes in the eccentricity of the elliptic orbit around the sun vary with a period of about 100,000 years. variations in obliquity (angle of tilt) of earths axis have a period of about 41,000 years. changes in precession (direction of axis tilt) and point perihelion (close to sun) change 23,000 years
what are the natural influences of the energy imbalance?
plate tectonics
Volcanic activity
changes in solar irradiance
long term outgassing from oceans and volcanoes
what re the anthropogenic influences of the energy imbalance?
land use change
aerosol emission
ozone depletion
fossil fuel emissions
what is radiative forcing?
one of the most commonly used climate change metrics,
a measure of how the energy balance of the earth atmosphere system is influenced when factors that affect climate are altered
allows inter comparison between different potential climate change mechanisms
how much has CO2 content changed
since pre industrial times its increased from 280ppm to 396ppm in 2013 (over 40% increase)
how is the ozone layer formed?
formed in presence of sunlight only
needs mix of carbon monoxide or volatile organic compounds, water vapour, nitrogen oxides and sunlight
what are the steps in ozone depletion?
- emissions
- accumulation
- transport (to stratosphere)
- conversion (to reactive)
- Chemical reaction
- removal
what are the atmospheric conditions for efficient ozone depletion at the poles?
low temps (formation of PSC) isolated conditions (chemical processes) polar stratospheric clouds
what are the environmental impacts of ozone depletion
decrease in stratospheric ozone layer has small cooling effect of global temps
when should a full recovery of the global ozone in mid latitudes be made?
2050
what conditions are required for ozone photosmog
high NOx emissions required
large concentrations of VOCs lots of sunlight
low wind speed and atmospheric stable conditions (inversion)
what are the IPCC representative concentration pathways (RCP)
a wide range of scenarios for climate situations
what is global warming?
increase in global and annually averaged air temp near the surface
what is climate change?
describes a significant and persistent change in the mean state of the climate or its variability. As such its nit exclusively tied to temperature change.
