Chapter 8-Circulation Of The Atmosphere Flashcards
Solar radiation absorbed vs emitted in polar latitudes? Specify latitude range
Polar latitudes (~38°-90°) lose more heat to space than they gain
What is the average balance of incoming solar radiation absorbed vs emitted in tropical latitudes? Specify latitude range.
Tropical latitudes (0~38°N/S) gain more heat than they lose to space (more incoming solar radiation absorbed by Earth than emitted by Earth)
How does solar energy input vary with latitude?
Sun’s rays strike parallel to surface at poles, and at a low angle in high latitudes (polar region), favoring reflection. Sunlight is spread over a greater surface area near poles (less radiation received per surface area unit). Also: Ice near poles reflects much of energy back into space; Light must filter thru more atmosphere.
Tropical latitudes receive much more solar energy. Sun’s rays strike perpendicular to surface at Equator; in tropics, angle of incidence more nearly vertical than in polar regions–>same amt of sunlight spread over smaller area. Also: less atmosphere to pass thru (minimizes reflection).
Mid latitudes receive more heat in summer than winter, esp Northern Hemisphere (3x more heat in summer)
Think of distribution (angle, surface area, seasons) and interference (reflection-atmosphere, reflection-ice, more land in Northern Hemisphere)
How is most heat transferred from equatorial regions to poles?
2/3 of poleward transfer of heat comes from water vapor in masses of moving air (atmospheric circulation of H2O vapor); this is bc of water’s extremely high latent heat of vaporization (540 cal/g–energy is stored as PE when water evaporates and released when water condenses). Ocean currents move remaining 1/3
How does the ocean transfer heat poleward? How much heat does it move?
Ocean currents are responsible fo about 1/3 of poleward heat transfer
Convection current
Circular current of air caused by air density gradient (difference in air density) resulting from temperature gradient (difference in temperature). Air warms, expands, becomes less dense and rises–then cools, contracts, becomes more dense, and falls.
Factors governing global circulation
Uneven solar heating, Earth’s rotation (Coriolis effect–eastward rotation of Earth on its axis, deflecting motion of any object with mass away from its initial course. RELATIVE to observer’s moving frame of reference on spinning Earth. No movement–no coriolis effect. Not on earth–no coriolis effect). Q
Coriolis effect
*Important factor in atmospheric circulation. Apparent curved deflection of the motion of any object with mass as it moves across the globe. Caused by eastward rotation of Earth on its axis. Relative to observer’s position on Earth. Motion is deflected clockwise (to the right) in Northern Hemisphere. Deflection is counterclockwise (to the left) in Southern Hemisphere. Hurricanes spin counterclockwise in NHem. Hurricanes spin clockwise in SHem.
Earth rotating 1638 km/hr @ Equator, 1/2 that at ~60°N, almost stationary at poles.
Explain how hurricanes work
Conditions: . High pressure air moving inward twd eye (low pressure air), deflected by Coriolis effect (tugged to the right–>counterclockwise spin in Northern Hemisphere; tugged to left–>clockwise spin in Southern Hemisphere)
Coriolis effect and atmospheric circulation
Coriolis effect is why air doesnt travel in one continuous loop between equator and poles in each hemisphere. Affects the direction of winds. Air rising from equatorial regions is gradually deflected eastward of its motion as it travels poleward–to the right in NHem and to left in SHem. 3 atmospheric cells in each hemisphere, 6 atmospheric circulation cells total.
Air circulation patterns, 0-30°N/S
1) Hadley cell or tropical cell: Air descending at tropics (30°N/S) reaches surface and as it moves back twd Equator is deflected by Coriolis. NHem Hadley cell: surface air deflected to right–> blows across ocean or land from northeast giving northeasterly trade winds; air warms as it moves equatorward, evaporating surface water, becoming humid and less dense->begins to rise as it approaches Equator.
Hadley cell
Air circulation cell in tropics (0-30°N/S), caused by uneven solar heating and affected by Coriolis effect. Poleward-moving air rises at Equator and loses moisture thru precipitation (expansion and cooling, losing energy, condensation and precipitation). Air is now drier (denser) and in upper atmosphere, where it radiates heat to space and cools (becomes increasingly dense). About 1/3 of the way to the pole (~30°N/S), air is dense enough to deGives rise to Northeasterly trade winds. One of three main air circulations cells.
Air circulation patterns, 30~50[60]° N/S
Ferrell cell. Some of descending air turns poleward (not equatorward), at high altitude joined by air returning from north before descending–driven by uneven heating and influenced by Coriolis. Surface wind deflected to right of its motion, flowing from west to complete circuit and creating Westerlies.
Where heat gained from absorbed incoming solar radiation equals heat lost (emitted by Earth)
@ about 38°N and 38°S latitudes
What is a hurricane? (Briefly)
Severe storms formed from interaction between sea and air, defined by high-velocity winds that rotate around a central, low-pressure core. They form over tropical oceans between ~5-20° latitude, where seawater is warm enough, and Coriolis effect is strong enough to make them spin (no Coriolis at equator). Similar tropical storms are called cyclones or typhoons in other parts of the world.
