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Which part of the electromagnetic energy spectrum emitted by the sun accounts for the largest influx of solar energy to Earth, and why?
Visible light (0.4-0.7 micrometers), because Wein’s law divides 2898 by the temperature (5780) to find the wavelength of maximum energy flux output
Which part of the electromagnetic energy spectrum accounts for the largest outflow of energy emitted by the Earth to space, and why?
Infrared (5-20 micrometers) because Wein’s law divides 2898 by the temperature (288) to find the wavelength of maximum energy flux output
What is the primary reason the tropics are consistently warmer than the polar regions throughout the year?
Earth’s spherical shape means that incoming solar radiation hits the tropics at a more direct angle than the poles, so they absorb more energy
What is the solar constant? If the solar constant for Earth’s orbit is S0, what is the amount of solar energy flux available to drive the climate system?
1367 W/m2. Average available energy is ¼ of solar constant?
How is the effective (emission) temperature of a planet determined? What is Earth’s effective temperature?
By finding the difference between its incoming and outgoing radiation. Earth’s effective temperature is 255K.
How does earth’s effective temperature compare to the actual observed global mean surface temperature? Is they differ, what accounts for the difference?
Earth’s actual observed temperature is 288K. The difference is caused by the atmosphere reflecting back outgoing radiation (greenhouse effect), so the Earth’s temperature rises to balance this increased radiation
What are the primary constituents of Earth’s atmosphere?
Nitrogen (78%) and oxygen (21%)
What are the main greenhouse gases in Earth’s atmosphere?
Water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and CFCs
What is the atmospheric greenhouse effect?
When greenhouse gases in the atmosphere reflect outgoing radiation back down to Earth, raising Earth’s temperature. Longwave absorption by the atmosphere reduces the efficiency of Earth’s cooling to space → surface “overheats” to balance incoming radiation.
What are the main anthropogenic greenhouse gases in Earth’s atmosphere?
Carbon dioxide, methane, nitrous oxide, and CFCs
What role do clouds play in Earth’s climate system? Do they cool or warm the Earth’s surface, and why?
Low, thick clouds cool earth by reflecting incoming SW radiation (increasing albedo). High, thin clouds warm earth by reflecting outgoing LW radiation (increasing). Net cloud forcing is a cooling effect.
Why does temperature decrease with height in the troposphere, but increase with height in the stratosphere?
Temperature decreases with height in the troposphere (closest layer to Earth) because it is heated from below by outgoing radiation from Earth. Temperature increases with height in the stratosphere because it is heated from above by the ozone layer at the top of the stratosphere, which absorbs UV radiation (heat).
Why is the radiative equilibrium vertical temperature profile unrealistic?
It is unrealistic because the warm surface + cold upper troposphere would lead to instability/convection mixing air vertically, transferring heat from the surface to the upper atmosphere.
What is the ideal gas law, and what are its implications for an air parcel moving vertically in the atmosphere?
PV = mRT (pressure x volume = amount x ideal gas constant x temperature). Rising air parcel will decrease in pressure. Volume could increase or temperature could decrease — need to know other conditions to tell.
What is hydrostatic balance, and why does atmospheric pressure decrease nearly exponentially with height?
The balance between the downward force of gravity and the upwards pressure gradient force. ΔP/Δz (pressure gradient) = - ρ (density) * g (gravitational constant). Pressure decreases with height because it is dependent on the weight of the air above it, which gets exponentially lower as you go up. /////
What is an adiabatic process, and how does the temperature of an air parcel change as it rises adiabatically in the atmosphere?
An adiabatic process is one in which no heat is taken or removed from the system. As an air parcel rises adiabatically in the atmosphere, it cools because it expands/pressure decreases.
How does the temperature of an air parcel change as it descends adiabatically in the atmosphere?
Temperature increases because pressure increases.
What is the difference between the dry adiabatic lapse rate and the environmental lapse rate?
The dry adiabatic lapse rate is a constant as long as the air remains unsaturated. The environmental lapse rate is the real observed change in temperature with height, and varies by location/conditions.
What are some of the ways Earth’s surface lose heat to the atmosphere, aside from radiative processes?
Thermal circulation and evaporation ////
Why is water (in its solid, liquid and vapor forms) crucial to Earth’s climate system?
Radiative properties (absorbs infrared radiation) and thermodynamic properties (phase changes, specific + latent heat) ///
Vapor pressure
The contribution (partial pressure) of water vapor to atmospheric pressure within a given air mass. Unit is hPa
Saturation vapor pressure
The water vapor pressure at which equilibrium, or evaporation = condensation, occurs. Aka the water holding capacity of the air.
Relative humidity
The ratio of actual vapor pressure to saturation vapor pressure (in %)
Dew point temperature
The temperature at which water vapor in the air condenses when air is cooled under constant pressure
If an air parcel is unsaturated, what processes can lead it to reach saturation?
By cooling (either by rising or from radiation) or adding water
What is the Clausius-Clapeyron relationship?
Saturation vapor pressure increases with temperature
What is the moist adiabatic lapse rate, and why is it different from the dry adiabatic lapse rate?
It is the measure of temperature decrease when a saturated air parcel rises in the atmosphere. Unlike the dry adiabatic lapse rate, it varies with temperature and pressure (not a constant)
How do clouds form in the atmosphere, and what is the lifting condensation level?
Clouds form when air rises and cools to the dew point/hits 100% saturation, so water vapor in the air condenses into liquid (clouds). Lifting condensation level is the height at which this occurs.
Why do mountains play such an important role in shaping local climates?
Mountains lift air up as it blows against the slope → air cools and forms clouds → windward side gets lots of rain/lushness → leeward side gets little rain, often warm and dry ////
What is the primary driving force for horizontal air movements in the atmosphere?
Pressure gradients produced by thermal or dynamical effects
What is the Coriolis force, and what factors determine its direction and magnitude?
The Coriolis force stems from Earth’s rotation and deflects moving objects to the right in the Northern hemisphere and to the left in the Southern hemisphere. Its direction and magnitude depends on the speed of the object, the latitude, and Earth’s rotation speed. Increases with wind speed. Increases as you move away from the equator.
Coriolis force equation
Acceleration = 2 x Omega (rate of rotation) x sin(latitude, aka phi) x velocity. Rate of rotation = 7.27 × 10-5 /sec. Coriolis parameter = 2 x Omega x sin(latitude)
What is the geostrophic balance? Why do geostrophic winds blow parallel to isobars in the upper atmosphere, rather than crossing the isobars from high to low pressure? Can you draw a force diagram illustrating the geostrophic balance?
Geostrophic balance is the force balance between the pressure gradient force and the Coriolis force. Wind continually bends to the right (NH) or left (SH) until it blows parallel to the isobars (this happens in the upper atmosphere bc no friction, lower atmosphere is diff).
What are the primary forces that determine air movements near Earth’s surface? Can you draw a diagram depicting the balance of forces at the surface?
Pressure gradient force, Coriolis force, and frictional force. Frictional force drags backwards against direction of flow, weakening Coriolis force (since Coriolis is proportional to wind speed). Because PGF is not proportional to wind speed, this tilts the wind flow slightly in the direction of the PGF.
How do winds blow around areas of low pressure in the Northern Hemisphere (Southern Hemisphere)? How about around areas of high pressure?
NH: counterclockwise for low pressure, clockwise for high pressure. SH: clockwise for low pressure, counterclockwise for high pressure.
What factors determine the magnitude of the geostrophic winds?
Determined by strength of pressure gradient/closeness of isobars. Stronger PGF = stronger wind.
What is the primary energy source for midlatitude cyclones?
Baroclinic instability → gravitational potential energy caused by having warm and cold air next to each other (temperature contrasts)
What is a cold front? A warm front?
Cold front = cold air mass displacing warm air mass. “Bulgy” shape because friction at the surface slows the lower part down. Warm front = warm air riding up over cold air at the surface. Usually not very steep
What typical weather patterns are associated with a cold front? With a warm front?
Intense rain in front of cold front (strong vertical motion/instability creates clouds), widespread rain in front of warm front. ////
When a high pressure system is passing through your area from the west, what temperature changes can you expect in your area?
idk come back ////
Why are numerical weather forecasts never 100% accurate?
Inaccurate/imprecise observations, model errors, chaotic/complex systems
What are some of the favorable conditions for tropical cyclone formation?
Surface convergence (air blowing together, low pressure zone), conditionally unstable atmosphere, warm sea surface temperature, weak vertical wind shear, Coriolis force (not too close to equator)
How does vertical wind shear affect tropical cyclone development?
Strong wind shear spreads the storm’s latent heat over a larger area and weakens the storm’s strength, making it less likely that a tropical cyclone develops (aka weakens it)
Energy source of tropical cyclones
Latent heat: when water condenses into liquid (moist air) after evaporating from the (warm) ocean surface it releases heat. Warm air rises → creates low pressure zone → air spirals in → tropical cyclone
In general, how do tropical cyclones move? Where is the most likely region in the United States for hurricanes to make landfall?
They generally move westward and curve towards higher latitudes (following the subtropical anticyclones/high-pressure systems (like above the ocean gyres?). They are most likely to make landfall along the Gulf Coast/East Coast.
How do tropical cyclones differ from (or resemble) midlatitude cyclones?
Differences: 1) energy source: midlat = gravitational potential energy, tropical = latent heat release. 2) structure: midlat = frontal (warm and cold fronts), tropical = warm core (with eyes). 3) formation region: midlat = over midlatitude land + oceans, tropical = only over tropical oceans. 4) time of year: midlat = all year round + strongest in winter, tropical = late summer/early fall. Similarities: rotational storms, strong low pressure centers, destructive systems that can have strong winds + precip
What is the relationship between El Niño and hurricane activity in the Atlantic and Eastern Pacific, and why?
El Nino is associated with fewer/weaker hurricanes in the Atlantic and more/stronger hurricanes in the Eastern Pacific. This is because El Nino leads to increased wind shear in the Atlantic (weakens hurricanes) and reduced wind shear in the eastern Pacific (stronger hurricanes).
How might global warming impact the intensity or frequency of tropical cyclones?
Strengthens: 1) increase in sea surface temperature 2) increase in atmospheric temperature 3) increased moisture in atmosphere. All lead to more favorable conditions for cyclone development. Greater frequency and intensity, longer seasonal duration, and may shift them polewards
In which latitudinal regions does the Earth’s climate system receive more heat from the sun than it radiates back to space? Where does it receive less heat?
It receives more energy that it gives out in the tropics, and receives less than it give out in high latitudes.
In which regions does most of Earth's precipitation occur, and why?
Most precipitation is in tropical regions and the monsoon areas of Southeast Asia because these areas receive the most solar energy. Convection and moist air cause air to rise, condense, and precipitate. also 60 N? ////
In which regions of the Earth are deserts typically found?
Deserts are typically found over land at 30 away from the equator, because this is where the sinking branch of the Hadley cell is found. It is warm because the air is sinking and compressing but it is dry because it has already lots its moisture over the rising zones.
What causes the formation of the Hadley cell, the trade winds, and the Inter- Tropical Convergence Zone (ITCZ)?
Solar energy hits the earth at the most direct angle at the equator (bc of sphere shape), causing excess heating in the tropics and forming the ITCZ. The air rises, diverges polewards, and then sinks again due to atmospheric instability. The surface return flows towards the equator in the Hadley cells are deflected by the Earth’s rotation, forming the easterly trade winds.
What are the prevailing surface winds in the midlatitudes of both the Northern and Southern Hemispheres, and why?
In the midlatitude Farrell Cells, wind returns polewards and the Coriolis force deflects it right. Therefore the prevailing surface winds flow northeast in the NH and southeast in the SH.
How can the Earth’s climate zones be described based on the general circulation of the atmosphere + what drives them?
Tropical climates in the tropics, dry climates ~30 degrees (sinking convection), temperate and continental climates in the midlatitudes, and polar climates at the poles.
Factors determining climate zones
Incoming solar radiation, atmospheric and ocean circulation, land-ocean distribution, and topography (mountains)
What is an Ekman spiral?
As the friction force of wind drags water along with it, the Coriolis force moves the water slightly to the right/left of the wind. Each successively lower layer of the ocean follows the layer above it but is also dragged a little left/right by the Coriolis force, so it forms a spiral all the way down. As energy is lost as you go down it gets so weak that the water is no longer moved.
Ekman transport + forces + direction
Eventually you have no more friction because the layers collectively balance out. Wind stress and Coriolis force act upon the entire column. Surface ocean currents move ~20 right/left of surface wind stress, but Ekman mass transport moves the whole column 90 perpendicular to the surface wind stress. The Coriolis force is always perpendicular to the ocean surface currents (right in NH, south in SH).
How does the wind pattern in the North Atlantic lead to high sea levels at the center of the subtropical gyre? Does this result in upwelling or downwelling?
Trade winds blow west across the bottom of the North Atlantic and east across the top. This creates a gyre in which ocean currents flow in a clockwise spiral. Ekman transport pulls water to the right in the northern hemisphere, so water is pulled into the center of the gyre (upwelling/convergence).
Coastal upwelling
Assume California. Wind blows south → offshore Ekman transport pulls water west (+ geostrophic current from north to south) → cool subsurface water wells up to replace missing water
Why does upwelling occur at the equator in both the Atlantic and Pacific Oceans?
Mass divergence at the equator because it’s between the ocean gyres (Trade winds) → water moves away from the equator → water upwells to replace it
What is geostrophic balance and how does it relate to geostrophic currents?
The hills in the ocean gyres create high pressure in that area. Underneath the surface, there is a horizontal pressure gradient between the high-pressure gyre center and low-pressure outside, so the PGF pulls water away from the gyre. Geostrophic balance is the balance between the Coriolis force creating this convergence zones and the PGF pulling it away, so ocean currents follow the isobars of the gyre.
What is El Niño?
The occasional return of unusually warm water in the normally cold water/upwelling region along the Peruvian coast.
What is the Southern Oscillation?
It is the “pressure seesaw” between the Western Central Pacific and the Eastern Central Pacific. Pressure in the two places has an inversely proportional relationship.
How is the Southern Oscillation Index typically defined?
Southern Oscillation Index is the sea-level pressure difference between Darwin, Australia and Tahiti (Tahiti - Darwin).
What is the relationship between the Indian monsoon and ENSO?
The Indian monsoon is weaker during El Nino and stronger during El Nina because during El Nino the air is sinking over the Western Pacific/India so it’s dryer, and during El Nina the air is rising over the Western Pacific/India so it’s wetter
What is the Bjerknes feedback?
Feedback loop that intensifies ENSO patterns. Ex: during El Nino, reduced contrast in ocean temperatures across the Pacific results in weaker trade winds → weaker trade winds leads to further reduction of upwelling in Eastern Pacific → warmer sea surface temperatures in Eastern Pacific → reinforces initial El Nino conditions. (vice versa for La Nina)
ENSO and wind/current direction, convection
El Nino = shift in surface wind/etc towards the east. La Nina = shift in surface wind/etc towards the west.
Describe the conditions in the tropical Pacific during normal, El Niño, and La Niña events, in terms of locations of convection, sea surface temperature anomalies, sea surface height, and thermoclines
ugh skip come back later
What are some of the other modes of climate variability and their associated indices?
not included, right?
Ultimate driver of climate system?
Sun and its radiative energy
How does solar radiation reach Earth?
Electromagnetic waves
Properties of solar radiation
Sun radiates as a black body, with temperature of ~6000 K. Radiates in visible band of electromagnetic spectrum
How much solar energy reaches location of Earth?
1367 W/m2 (solar constant)
What percentage of solar constant is available to drive the climate system, and why?
¼ (because of Earth’s sphericity)
How much of incoming solar radiation does Earth reflect, and what is the primary reason?
30%, mostly due to clouds
What is radiative equilibrium + what is Earth’s emission temperature?
When the earth radiates the same amount of energy as it receives from the sun, resulting in an emission temp of 255K
What is the greenhouse effect?
Atmospheric absorption of outgoing infrared/longwave raditation emitted from Earth’s surface
How does nitrogen interact with LW and SW radiation?
Transparent to both
How does oxygen interact with radiation?
Absorbs mainly UV (SW) radiation
How do minor atmospheric constituents interact with radiation
Absorb LW radiation (from Earth’s surface)
How much does radiation the earth have to allow 235 W/m2 to escape and balance the incoming 235 W/m2 from the sun + what is the resulting average surface temperature?
Earth has to emit 390 W/m2, average surface temp is 288K (?)
Where is planetary albedo the largest and why?
In the poles because of ice cover
What percentage of total planetary albedo is due to clouds?
Clouds contribute to half of total planetary albedo
Which decreases more slowly towards the poles: incoming solar radiation or outgoing radiation?
Outgoing radiation (lower diff between poles and tropics)
How do deep cumulonimbus clouds impact temperature?
The both cool and warm, with a net neutral effect
How does climate change impact cloud forcing?
CC will have a net warming effect on clouds → positive feedback loop. Rising high clouds and fewer lower clouds warm further. include the cold forcing ones too?
What is the radiative equilibrium temperature profile?
Temperature at diff altitudes if you only considered incoming and outgoing radiation (?)
What is convection?
Transfer of heat through vertical motion of air parcels
What are the three laws governing atmospheric convection?
1) Ideal gas law: compressibility of atmosphere. 2) Hydrostatic balance: governing buoyancy of gas parcels under gravity 3) First law of thermodynamics: conservation of heat energy and work
What percent of atmospheric mass lies above the troposphere?
About 10%
What is the adiabatic cooling rate?
9.8 degrees C per km
What happens if an atmosphere cools faster with height than the adiabatic rate?
It will be unstable and get adjusted to the adiabatic rate through convection
What is the average moist adiabatic lapse rate (though not a constant)?
6.5 K/km
What does baroclinic instability do?
Converts available gravitational potential energy to kinetic energy (moves horizontal temp differences to vertical)
What drives atmospheric general circulation?
Radiative imbalance at top of atmosphere (differing incoming solar radiation)
What creates the subtropical jet stream?
Hadley cell moves air polewards at top of atmosphere → Coriolis force (conservation of angular momentum) directs it east
What drives the Ferrel cell?
Eddies/midlatitude cyclones are created by baroclinic instability and transport energy from midlatitude to high latitudes ////
What creates subtropical high pressure zones?
Sinking branch of the Hadley cell
How deep do Ekman spirals go?
300 meters
What is western boundary intensification/currents (NH) and what causes it?
Eastward high latitude surface currents in ocean gyres are subject to high Coriolis force (picture ocean gyres) → eastward currents deflect towards the equator (in NH, right) → currents never really reach the east ocean/west coast. Westward currents are near the equator, so weaker Coriolis force → go all the way up to the west ocean/eastern coast → currents are more intense there
