Atmospheric and Ocean Circulation Flashcards
Natural and anthropogenic CO2 increase
- More than 1/2 of the observed temperature
since 1951 is caused by human forcing - Oceans observing twice as much heat since
1997
ENSO
El Niño Southern Oscillation
- El Niño and La Niña alternate every 2 to 7
years
Normal El Niño conditions
- Pacific Ocean absorbs a large volume of
solar heat = fall in atmospheric pressure
around the western tropical pacific - Trade winds flow in an east to west direction
causing a westward migration of warm water
= warm pool along the coast of countries
located in the west Pacific - Upwelling in the east as colder water, from
deep within the ocean, rises up to replace
the loss of the warmer water from the
western coasts - A temperature difference occurs between
the east and west pacific - Increase in surface temperature of the ocean
in the east results in the warm air to rise up
into the atmosphere more vigorously =
powerful storms in the west
El Niño
- Rising air in the east causes the
thunderstorms that were experienced in
western Pacific countries to affect those
located in the south - Normal weather conditions is reversed during
an El Niño with warm water being present in
the east - Drought = Australia, Indonesia
- Heavy rains normally occur along the west
coast of South America due to warm air
rapidly rising up into the atmosphere
La Niña
- Higher atmospheric pressure and much
cooler temperatures in comparison to the
normal conditions - Colder temperatures shift from being in the
west to the east; therefore the conditions
experienced during a La Niña is the opposite
of what occurs during an El Niño - Droughts typically occur in areas such as
South America - Heavy rainfall in the western countries such
as Indonesia - Colder temperatures cover the majority of
equatorial areas in comparison to the other
conditions.
Atmospheric structure
- All weather occurs in the troposphere
- Extends 12km above surface
- 80% mass
Energy in the atmosphere - conduction
- Heat energy is transferred via contact to
neighbouring particles - Air is poor conductor so conduction occurs at
the surface
Radiation
Transfer of heat energy without the physical substance e.g. the Suns electromagnetic wave
Convection
Heat energy transferred by movement of molecules with a substance. Both water and air transport heat by moving energy particles
Heat capacity
Heat energy required to change the temperature of an object by a given amount. Water has a higher capacity than land
Latent heat
Is the transfer of heat (also through convection) but the energy is hidden in the form of water.
Water has a higher heat capacity - can hold 4 x more gas in the atmosphere
The amount of water vapour air can hold depends on temperature
Saturation vapour density
Measure of how much H2O air can hold
Latent heat energy more explained
- Air much better at transporting
energy in medium to high
latitudes - higher latitudes = takes the bulk
of the heat - Warm tropical air (30 degrees
Celsius) holds 10 x more water
than in the poles
Lower latitude energy
Surplus
Higher latitude energy
Deficit
Transport of heat
Ocean is most important in transporting heat out of the tropics
Circulation patterns controlled by
- Heating by solar radiation
- Pressure gradient force
- Coriolis force
Coriolis force
The force that causes a deflection of objects as they move across a rotating surface
Model 1: single cell, non rotating
- non rotating
- no Coriolis force
- pressure gradient force
Model 2: single cell rotating sphere
- rotating and so a Coriolis force
Model 3: three cell rotating sphere
Three cells:
- Hadley cell (0-30*)
- Ferrel cell (30-60*)
- Polar cell (60-90*)
Coriolis force
Hot air continues to rise at 30* and not at the poles
Doldrums
Belt of low pressure that forms around the equator
Ocean gyres
Result of the initial drag of the winds. Largely driven by atmospheric system
Ekman transport
Results in major direction of ocean movement to be 90* to the direction of the wind
Centre of gyres are 2m higher in Atlantic
Occurs at the coast
Feedbacks
Processes that alter climate changes already underway, either amplifying (positive) them or suppressing (negative) them
Water vapour
POSITIVE and REVERSIBLE
Most efficient ghg trapping radiation - triples the amount of warming
Initial change
|
\/
Climate warming
|
\/
Increased atmospheric water vapour
|
\/
Increase ghg trapping of radiation
|
\/
Increased warming
Albedo
POSITIVE
Important for glacial = cooling
Instant change
|
\/
Climate cooling
|
\/
Increased snow and ice: higher reflectivity
|
\/
Less solar radiation absorbed at surface
|
\/
Greater cooling
40% amplification
Vegetation
POSITIVE and REVERSIBLE
Forest replacing grassland increasing water vapour in the atmosphere - increasing moisture for precipitation
Initial change
|
\/
Increased precipitation
|
\/
Forest replaces grassland
|
\/
Increased transpiration of water vapour
|
\/
Additional precipitation
Initial change
|
\/
Warmer climate
|
\/
Increased temperature, precipitation and vegetation
|
\/
Increased chemical weathering
|
\/
Increased CO2 removal by weathering
|
\/
Reduction of initial warming
