Climate Flashcards
Lecture 4: Jan 29
Define weather.
Hour-to-hour, day-to-day variation in temperature and precipitation.
Define climate.
Typical atmospheric conditions that occur throughout the year.
What is climate driven by? What is it responsible for?
Driven by unequal heating of the atmosphere by solar radiation, atmospheric and oceanic currents, and Earth’s rotation.
Responsible for different biomes.
Describe solar radiation. What does it drive?
Energy emitted by the sun in the form of waves.
The visible light range drives photosynthesis by plants, allowing them to bind CO2.
Describe the greenhouse effect.
Naturally occurring gases keep the Earth’s temperature warmer than it otherwise would be.
What are terrestrial biomes defined by?
Major vegetation types.
What are the natural sources of greenhouse gases?
- H2O (water vapor): oceans, lakes, land surface, plants.
- CO2 (carbon dioxide): respiration, decomposition.
- CH4 (methane): anaerobic decomposition.
- N2O (nitrous oxide): wet soils, low oxygenated water.
- O3 (ozone): UV light breaks apart O2 which then combines with O2.
What are anthropogenic sources of greenhouse gases?
CO2: Burning fossil fuels.
CH4 & NO2: Agriculture, landfills, fossil fuels.
CFCs (chlorofluorocarbons): Aerosol propellants, refrigerants – VERY potent gases!
Where are greenhouse gases primarily absorbed?
Earth’s surface.
What primarily absorbs IR emissions from Earth?
Greenhouse gases.
Differences in solar radiation received between locations on the Earth’s surface depends on what four things?
- The angle of the sun striking different parts of Earth (impacts amount of atmosphere it must travel through).
- Depth of the atmosphere light passes through.
- Albedo: amount of light reflected back to space.
- The season (tilt of the Earth relative to the sun).
What is albedo?
Fraction of sunlight reflected back into space.
Has strong effects on local weather conditions.
What affects albedo?
- Lightness/darkness of a surface (white reflects more than black).
- Vegetation and urban areas absorb more solar radiation.
The high albedo of polar ice caps contributes to them being…
Colder and being the color white (reflects light more to make it colder)
What is the solar equator? What effect does it create?
Where the sun is directly overhead; strikes the Earth most intensely.
Seasonal heating of the Earth.
What latitudes does the solar equator fluctuate between?
23.5* N (June) - 23.5* S (December).
Atmospheric currents are driven by what?
Uneven heating of the Earth.
Describe the formation of Hadley cells.
Warm air (holds H2O, less dense) rises at the ITCZ.
As it rises, the air cools and water vapor becomes rain (cool air can’t hold much H2O).
The cool, dry air is pushed N/S by more rising warm air.
As the cool air becomes more dense, it drops (compresses and becomes warm and dry) around 30* N/S.
The air flows back toward the equator and is re-humidified from the Earth’s surface.
Why are most deserts at 30* N/S?
Due to Hadley cells.
What is the ITCZ?
Intertropical Convergence Zone (where two Hadley cells converge).
Why does most rainfall occur in the tropics (between 23.5* N/S).
Due to the solar equator (uneven heating) causing Hadley cells to form.
How do fluctuations in the solar equator affect rainy seasons at locations close to the equator compared to closer to the tropics (Capricorn, Cancer)?
At equator: two rainy seasons.
Close to tropics: one rainy season.
Along with the solar equator, what else has an effect on where rain falls and certain aspects of seasonality?
Geographic features (though to a lesser extent).
Describe polar cells.
Located 60-90* N/S.
Air rises at 60* N/S and drops moisture. Cool, dry air moves to the poles where it drops and cycles back to 60* N/S.
Describe Ferrel cells.
Located 30-60* N/S.
Indistinct air movements. Mixes tropical and polar air.
How do polar cells affect rainfall?
Around 60* N/S there is a lot of precipitation. Creates taiga.
Much precipitation is snow and much water is locked away as permafrost.
Polar regions are col deserts (very little evaporation. High albedo. Cold, dry air.)
What is the Coriolis Effect?
The Earth’s rotation causes circulating air to be moved to the right going N and to the left going S from the equator.
What is the rotation speed of the Earth at the equator versus at the poles?
E: 1670 km/hr
P: 291 km/hr
Describe westerlies.
Surface wind moving toward the poles moves faster than the Earth’s surface. (West to East. FROM the west, not going west).
Describe trade winds.
Surface wind moving toward the equator moves slower than Earth’s surface. (Blow East to West)
What drives ocean currents?
- Unequal heating.
- Coriolis effect.
- Wind direction.
- Ocean basins & contents, salinity.
Which way do trade winds push ocean currents? (Equatorial currents).
Westward.
Which way do westerlies push ocean currents? (N Pacific current, N Atlantic current).
Eastward.
What are gyres? What causes them?
Large oceanic circulation patterns moving clockwise in the N hemisphere and anticlockwise in the S hemisphere.
Caused by the currents created by trade winds and westerlies.
What are upwellings? Why are they important?
Upward movement of ocean water as surface waters move away from the continent.
Allows key nutrients to be brought up from ocean depths. Help determine location of commercial fisheries (often on the W of continents).
What is thermohaline circulation? Why are they important?
Ocean currents driven by variation in temperature and salinity.
Responsible for connecting all major oceans. Help to redistribute energy and nutrients among all oceans (cycle may take hundreds of years).
What small-scale geographic features affect climate?
- Albedo
- Proximity to coast (coastal regions are more moderate, inland regions more extreme)
- Rain shadows
What causes rain shadows?
High mountains force winds upward; as they cool, they drop rain, leaving warm, dry air on the other side.
