Quiz 2 Flashcards
Incoming Solar Radiation
- Earth is a three-dimensional sphere
- 340 W/sq.m of solar radiation arrives at the top of the atmosphere
- Earth retains ~70% of this radiation
Earth–Atmosphere Radiation Balance
Solar radiation arriving at the top of Earth’s atmosphere averages 340 W/m2, indicated here as 100%.
About 30% of the incoming radiation is reflected and scattered back to space, and the other 238 W/m2 (70%) enters the climate system. Some of this entering radiation warms Earth’s surface and causes it to radiate heat upward.
The greenhouse effect retains 95% of the heat radiated back from Earth’s heated surface and warms Earth by 31°C.
The Greenhouse Effect
- An average temperature on Earth today is +15.5ºC (59°F)
- Without the greenhouse effect an average temperature on Earth would be minus 18ºC (-0.4°F)
albedo
- Albedo is the fraction of solar radiation reflected from the Earth back into space
- Albedo is a measure of reflectivity of the surface (or material)
Albedo-Temperature feedback
- Its net effect increases Earth’s sensitivity to climate change
- Most strongly affects climate poleward the snow and sea ice limits
Conduction
- movement of energy from one molecule to another w/o changes in their relative positions
- Metals are good conductors; air is a poor conductor
Convection
transfer of heat by a moving substance
Latent (stored) heat
Stored energy is released when water vapor changes into water (latent heat of vaporization) or water changes into ice (latent heat of melting)
General atmospheric circulation
Heated air rises in the tropics at the ITCZ and sinks in the subtropics as part of the Hadley Cell flow
Hadley cell circulation and the ITCZ
Warm moist equatorial air rises and forms clouds
- This air sinks in the tropics creating areas of high pressure
- at the surface air flows from the tropics toward the equator replacing the rising air
Coriolis effect
- Coriolis effect – the apparent deflection of free moving objects
- Cause – Earth’s rotation on its axis
- Objects moving away from the equator curve eastward
- Objects moving towards the equator curve westward
Water in the climate system
Only on Earth (of all the planets in our solar system) water can exist in three states:
- liquid
- solid (ice)
- gas (water vapor)
The Hydrologic Cycle
- Continuing recycling of water among three reservoirs
- Oceans contain 97% of Earth’s water
- Glaciers contain 2% of water
- Atmospheric moisture, surface and ground water, biological and soil water ~1%
Water vapor feedback
- Water vapor is the major greenhouse gas
- When climate warms, atmosphere is able to hold more water vapor, and the increase in water vapor leads to further warming by means of a positive feedback. This feedback works in reverse during cooling.
Heating properties of water
- Water has a high specific heat (1 calorie of heat energy is required to increase the temperature of 1 gram of water by 1°C within the range of 0°-100°C)
- High heat capacity of the ocean: water warms up and cools off slower than land
- Water has a slow response rate
thermal inertia
- Differences in amplitude and timing of response
- The fast-responding land has lower thermal inertia than slow-responding upper ocean layer
What is the pressure pattern over land and ocean in summer?
Air motion associated with monsoon circulations at larger scales is upward over the land and downward over the ocean in summer
Where does the heaviest precipitation occur?
regions of low pressure (Pr) and upward motion.
How does the pressure and precipitation situation change in winter?
downward over land and upward over ocean in winter
Cloud formation: Adiabatic Processes
- The term adiabatic literally means ‘not to be passed‘
- The parcel of air does not exchange energy with the surrounding (environmental) air
all clouds form by the process of Adiabatic Cooling of rising Air
- ascending parcel of air cools adiabatically by expansion
- Air must be saturated for condensation (cloud formation) to start
- Lapse rate - the rate at which Earth’s atmosphere cools
- Average lapse rate 6.5°C/km
Orographic precipitation in mid-latitudes
Low-pressure cells move rapidly from west to east
They interact with the regional topography
Heat transfer in oceans
Uppermost layer is heated by the Sun
Like air, water expands and becomes less dense and sits on the colder denser water layers.
Wind mixes the heat to 100m
Some water is transported to the poles.
Is there any global pattern in the distribution of cold and warm surface currents?
In the Northern Hemisphere, mid-latitude southwesterly
winds and tropical northeasterly trade winds drive warm water toward the centers of subtropical gyres, forming a thick lens of warm water that circulates in a clockwise gyre.
Thermohaline circulation
- The permanent zone of rapid temperature change– thermocline
- Surface currents occur above the thermocline
- The permanent thermocline (100–1,000 m) separates cold deep water from shallower layers affected by changes in Earth’s surface temperature. Shallow seasonal thermoclines (0–100 m) vary in response to seasonal solar heating of the upper ocean layers.
Deep Ocean Circulation: The “Conveyor Belt”
Colder and more saline water sinks in three places: north of Iceland and east of Labrador in the Northern Atlantic, and around Antarctica
Effects of ice
- Seawater freezes at -1.9°C
- Sea ice rejects all the salt present in seawater
- Ice is less dense than water and floats on top of the ocean
Effects of Sea Ice
- When sea ice forms, it seals off the underlying ocean from water-atmosphere interaction
- Ice-covered ocean behaves like a continent covered with snow
- Whereas heat can escape from an unfrozen ocean surface, a cover of sea ice stops the release of heat from the ocean to the atmosphere in winter and causes air temperatures to cool by as much as 30°C
Mountain Glaciers
- Glaciers accumulate snow at higher elevations
- Snow turns to glacial ice through compaction and re-crystallization
- In the tropics glaciers can survive only at higher elevations while at high latitudes they exist at sea level
Continental Ice sheets
- The central portions of large ice sheets form high central domes
- Ice streams down the flanks and forms ice lobes and ice shelves
- Icebergs break off and float away
Carbon cycle
conversion from carbon dioxide to living matter (carbon) and back to carbon dioxide
Photosynthesis
converts CO2 to sugars; decreases CO2 amount in the atmosphere
Respiration
converts sugars to CO2; increases CO2 amount
Precipitation and vegetation
- Plants reflects the patterns of precipitation distribution
- High-biomass forests in the areas of low pressure (the ITCZ, mid-latitudes)
- Deserts in the tropical areas of high pressure
Albedo and vegetation cover
- When climate cools, conifers are replaced by tundra – albedo is increased
- When climate warms, more conifers absorb more solar radiation
precipitation and vegetation cover
- When climate becomes wetter, forests gradually replace grasslands
- Trees transpire more water vapor back to the atmosphere
