Chapter 8 - Air Masses Flashcards
What is George Hadley’s ‘Single-Cell Model’?
Hadley believed there was a single huge cell in each hemisphere, which is incorrect. He did note that differences in heating give rise to persistent large-scale motions called thermally direct circulations and that zonal winds can result from deflection of meridional winds.
What is the ‘Hadley cell’ and where is it found?
The Hadley cell is a large-scale wind and pressure pattern found in tropical latitudes of both hemispheres. Air rises above the equator, flows poleward to about 25 degrees latitude, subsides and flows back to the equator at low levels.
What are the 3 distinct cells of the Three-Cell Model?
- Hadley Cell (circulates air between tropics and subtropics)
- Ferrell Cell (located in middle latitudes)
- Polar Cell
Is the Three-Cell Model accurate in describing real weather patterns?
No. The Hadley circulation provides a good account of low-latitude motions, but the Ferrel and Polar cells are not quite as well-represented in reality.
What are ‘Rossby Waves’?
Also known as long waves, Rossby Waves are in the midlatitude westerlies and have wavelengths on the order of thousands of km. Often, a series of Rossby Waves circle the planet, forming a pattern of ridges and troughs.
What is the ‘Ekman Spiral’?
Ocean surface currents flow at an angle 45 degrees to the right (N hemisphere) of the winds that drive them and continue to shift clockwise as their speed decreases. At approx. 100 m, the current approaches the opposite direction of the surface current and begins to die out.
What is the meaning of the word ‘Monsoon’?
Monsoon refers to climactic pattern in which heavy precipitation alternates with hot, dry conditions on an annual basis. Monsoons are primarily experienced in Southern Asia and are caused partially by the Himalaya mountains.
What are ‘chinooks’?
When winds warmed by compression descend the eastern slopes of the Rocky Mountains, they are called ‘chinooks’.
What are ‘katabatic winds’?
Winds originating when air is locally chilled over a high elevation plateau. The air becomes dense because of its low temperature and flows downslope.
What is ‘El Niño’?
A recurrent event in the tropical eastern Pacific where ocean surface temperatures are significantly higher than normal.
What causes ‘El Niño’?
El Niño results from the Walker Circulation. The Walker Circulation is an east-west circulation pattern of the tropics. An El Niño develops when the trade winds weaken or even reverse and flow eastward.
What is ‘La Niña’?
La Niña is the name for the unusual cooling of the waters of the tropical eastern Pacific.
