Y13 Atmosphere Flashcards
Atmosphere define
The thin layer of gas surrounding a planet
Held by gravity
Factors affecting atmosphere size
Gravity
Greater = larger atm
Temperature
Lower temp = greater retention of atmosphere
Presence of a magnetic field
Outline the 4 phases of the history of earth’s atmosphere
Phase 1: earth’s formation
H and He pulled in by grav
Solar winds blow gases away
Phase 2:
Volcanic activity release H2O, CO2, NH3
Phase 3: earth cooled
H2O fell as rain, carrying CO2 to form oceans
Photosynthesis of oceanic algae release O2
UV radiation breaks NH3 into N2 and H2, H2 escapes into space
Phase 4:
Early life converts CO2 to C compounds
What is the soil atmosphere? CO2 content
Extends about 1m into the soil
Bacteria/fungi/plant roots perform respiration, so soil has higher CO2 and lower O2
Difference in conc causes diffusion of gases between soil and atm
5 reasons why the atmosphere is important
Part of the water cycle
Protect against UV
Provides O2 and CO2
Traps heat to create survivable temp
Transfers heat around the earth
What are the 5 layers of the atmosphere?
Closest to furthest:
Troposphere (80%)
Stratosphere (19%) ozone layer here
Mesosphere
Ionosphere / thermosphere
Exosphere (1% total) up to 800km
What is ozone and what does it do?
O3
Absorbs UV
Warms the stratosphere
What makes UV dangerous
UV radiation had energy to break chemical bonds
Ionisation - electrons break away from their atoms
Damage materials / living tissues
types of UV radiation and the ozone layer
Shorter wavelength = more penetrating and dangerous
UV-c most dangerous
Ozone layer absorbs 100% of UV-c and 95% of UV-b radiation
Formation and destruction of ozone via UV light
UV light below 240mm disrupts the bond of the O2 molecule
Forms 2 separate O atoms which join with O2 to form O3
Formation of ozone: UVC absorbed
UV light 240-315nm disrupts the bond of the ozone molecule, converting it back to oxygen
Destruction of ozone: UVB adsorbed
Anthropogenic ozone depletion
CFC molecules used (CFCl3)
UV causes one Cl to break away
Cl pulls O from O3, forming ClO and O2
Free O removes Cl, forms O2
Free Cl repeat cycle
Mesosphere
50km to 80km
Less than 1% of the atmosphere
Meteors burn up
Thermosphere
Contains the ionosphere
X rays and UC radiation absorbed
What factor impacts the height of the troposphere?
7-20km ASL
Widest at the equator and thinnest at the poles
Depends on AIR TEMPERATURE
Colder = particles closer together
Describe the temperature of the layers
Temperature gradient INVERTS at layers
Troposphere - higher, temp DEcrease
Stratosphere - higher, temp INcrease
Mesosphere - higher, temp DEcrease
Thermosphere - higher, temp INcrease
Why does the temperature of the Troposphere change the way it does?
Temp increases higher
Heat source is Earth’s surface
Moving away from heat source
Why does the temperature of the stratosphere change the way it does
Temp increase higher
Heat source Ozone layer
Chemical reaction that forms ozone releases heat energy
Cooler air already at the bottom, warm air sits above it. Little or no convection, hence stable
Why does the temperature of the mesosphere change the way it does
Temp decreases higher
Heat source stratosphere
Further away
Few gas particles present to absorb solar energy
Why does the temperature of the Thermosphere change the way it does
Temp increase higher
Solar energy absorbed by gas particles and re-emitted as heat energy
Particles can become very hot but few particles present so it ‘feels’ cold
Earth’s tilt
23.5 degrees from vertical in relation to the earth’s orbital plane around the sun (eliptic plane)
Hence 23.5N is Tropic of Cancer
23.5S is Tropic of Capricorn
Describe atmospheric circulation at the equator
Earth radiates heat to the air
Warm air rises at equator until it reaches the Tropopause
Deflected toward the poles, pushed by rising air
Convection currents formed
Cool air from sides move in to the equator to replace the rising air (trade winds)
Name the three circulation cells and the boundaries
Hadley cell (0-30)
Ferrel cell (30-60)
Polar cell (60-90)
Intertropical convergence zone between Hadley cells
Area of low pressure, no winds = doldrums
Horse latitude between Hadley and Ferrel cells
Polar front between ferrel and polar cells
Describe the Hadley cell system
The strongest of the three cells.
Warm rising air from equator moves N/S when it meets the tropopause
Air mass rises —> expands (less air pressure)
Cools and temperature drops, water vapour condenses to form clouds
Dry cool air moves towards poles and warms due to pressure, creating high region (subtropical high)
Describe the ferrel cell system
Driven by the Hadley and polar cells, NOT a hot/cold air source
Hence goes in the opposite direction, acting like a gear
Coriolis effect
Eddies - temp from warm to cold over a short distance
Describe the polar cell system
Cold dense air at poles sink (high pressure system)
Spreads toward equator, meets warmer tropical air (low pressure)
Similar cycle to Hadley cells
Latent energy define
The energy needed to change state
Features associated with low and high pressure zones
Low pressure - rising air. Much more rainfall (hence equatorial rainforests and relatively wet UK weather)
High pressure - little rainfall
Desert regions
Explain the coriolis effect
Equator moving “faster” relative to the poles
Different speeds at different latitudes
Hence air moving from tropics toward equator is slower, deflected left
Air moving from equator to tropics faster, deflected right
(Trade winds)
Anticlockwise in the northern hemisphere
Clockwise in the Southern Hemisphere
What are winds caused by?
Differences in air pressure.
Air moves from HIGH to LOW pressure areas, creating wind
Greater difference in pressure —> stronger wind
Winds are labeled by the direction they come from (westerlies from the west)
Describe the zones of air mass movement on earth
Six zones called Wind Belts
Formed from movement of air from high to low pressure
Top to bottom:
Polar easterlies
Westerlies
Northeast trade winds
Southeast trade winds
Westerlies
Polar easterlies
Describe the location and nature of jet streams
Narrow belts of high speed winds
High in the troposphere, just below the tropopause, near air mass boundaries with large temperature differences
Polar jet between polar and ferrel cells - very fast
Subtropical jet between ferrel and Hadley cells - slower
Flow parallel to temp gradient, moving West to East
How do jet streams affect weather?
**scholarship
Causes changes in wind pressure at a high level, affecting things near the surface.
Movement doesn’t have to be straight and smooth - this slows things, making areas of low pressure move less predictably
Slower jet stream cause areas of high pressure to strengthen
Can lower a low pressure system like a vacuum - sucks air out the top
Pressure gradient force
Pascals per meter
Eg low pressure at equator, high pressure at poles due to temp results in a pressure gradient,
Acts from high to low pressure
Describe how land/sea breezes work
Land heats up and cools down FASTER than water
Day: warm air over land rises, replaced by cool air from ocean = onshore breeze
Night: opposite = offshore breeze
Describe Walker circulation
A cycle of warm moist air from the Western Pacific (South America) rising, then cooling and falling at the Eastern side (Australia). Dry air circles back.
Caused by TRADE WINDS moving to the west
Mirrored by a cell in the ocean - drives the El Niño and La Niña events
What are hurricanes, typhoons and cyclones?
Tropical Storm systems created when ocean temperature exceeds 26C.
Large air masses circulating around a LOW pressure centre
Hurricane - America, Caribbean
Typhoon - SE Asia
Cyclone - Indonesia, Aust, NZ
What is a temperature inversion and what causes it?
In the troposphere, usually warm to cold higher up. Inversion is the opposite
Happens when air in contact with colder earth’s surface cools more than the air above (usually a clear/calm night)
Or interactions of cold and warm fronts
Causes fog - trapped ‘cloud’
main pressure belts
ITCZ Equatorial Low
Subtropical highs
Subpolar lows
Polar Highs
relates to where warm air is rising and cool air is descending (cells)
