Global Atmospheric Circulation Flashcards
What is global circulation?
In 1735 George Hadley declared that temperature contrasts between Poles and Equator drives global circulation.
The one-cell model for global circulation would work great except….
Works great for a non-rotating earth!
What does the rotation of the earth do to winds?
Rotation causes winds to be deflected
What do one cell and 3 cell models look like?
Look at power point on page 4. Make sure you know 3 cell model VERY well
What does a 3 cell model work best for?
A rotating, all water earth
What are the two general rules on pressure/weather relationship?
- areas of L have clouds and rain
* areas of H have fair weather High and Dry!
What is the equatorial low also called?
ITCZ (Inter Tropical Convergence Zone)
In the Inter Tropical Convergence Zone, why does air rise in the troposphere?
Air rises to tropopause due to intense heating (THERMAL LOW Pressure) diverges aloft and moves toward poles
What are light winds called in the Inter Tropical Convergence Zone?
Doldrums
What is the weather like in the Inter Tropical Convergence Zone?
Constant clouds and rain
What is found at (20º-35º) each hemisphere?
Subtropical High pressure (STH)
What happens to the air in the Subtropical High Pressure zone?
air aloft cools and sinks
Why does air cool in the Subtropical High Pressure zone? Why does it sink?
Air Cools due to radiative heat loss into space. Heavier cool air piles up aloft and sinks
What does cooling and sinking air create in Subtropical High Pressure zones?
Creates DYNAMIC High Pressure zone. Sinking air is warming = DESERTS!!!
What are trade winds?
Surface air flows from STH to ITCZ, deflected to right, produces steady easterly winds, 11-13 mph
What are prevailing westerlies? What happens to them?
Sinking air from STH diverges at surface and flows toward subpolar low between about 30º to 60º N & S, deflected by coriolis
What do the westerlies produce?
Stormy weather
Where are westerlie winds especially strong?
Winds are especially strong between 40-50° the Roaring 40s and in southern hemisphere
What is a subpolar low also known as?
Also called Polar Front (“front” = where 2 air masses meet)
What is a subpolar low (polar front)
Warm air (subtropics) vs. cold air (polar) around 60º…warm is forced up over cold, creating DYNAMIC LOW pressure at surface (NOT from thermal heating)
What is a polar high?
It is when air loses heat to space, and is chilled as it flows over snow/ice. It then sinks around poles forming Thermal High
What are polar easterlies?
Air flows from Polar H to Polar Front (L).
What happens to air in polar easterlies? What is it deflected by?
Air subsides at poles (H) and flows toward polar front (L), deflected by coriolis effect to easterly wind
The 3-Cell is an “all water world” MODEL. Real circulation pattern is much more complicated. Why?
Continents (landmasses) disrupt the ideal pattern of thermal pressure land heats and cools faster than water. This means there is uneven Heating of Land and Water
What are idealized winds?
Idealized winds generated by pressure gradient and Coriolis Force.
What are actual winds?
Actual wind patterns owing to land mass distribution.
What are the observed patterns of pressure cells?
LARGE Pressure Cells
What do continents disrupt?
Continents disrupt zonal (latitudinal) flow
Why do High and Low pressure cells form?
H and L Pressure cells form due to land/water contrasts and surface friction
What happens in the Southern Hemisphere?
In the S. Hemisphere, at mid and high lats (45º & 65ºS), a more zonal (latitudinal) pattern exists (like all water world). This is because there are Few and Smaller LAND SURFACES
What is important to know about pressure and wind belts?
Pressure & wind belts are NOT fixed they migrate N and S as sun’s direct rays move North and South
How many major high pressure cells are there?
5
What are winds named after?
Winds are named from where they come!!
What is a monsoon?
Seasonal Wind REVERSAL (caused by pressure reversal). Like a land/sea breeze but Operates on seasonal NOT daily schedule. (Major seasonal change in pressure, wind direction, and rainfall occurs)
Where do we find monsoonal climates?
India and South East Asia. There is also a North American Monsoon that is in SW US and N Mexico.
