Global Atmospheric Circulation

Question 1

What is global circulation?

Answer 1

In 1735 George Hadley declared that temperature contrasts between Poles and Equator drives global circulation.

Question 2

The one-cell model for global circulation would work great except….

Answer 2

Works great for a non-rotating earth!

Question 3

What does the rotation of the earth do to winds?

Answer 3

Rotation causes winds to be deflected

Question 4

What do one cell and 3 cell models look like?

Answer 4

Look at power point on page 4. Make sure you know 3 cell model VERY well

Question 5

What does a 3 cell model work best for?

Answer 5

A rotating, all water earth

Question 6

What are the two general rules on pressure/weather relationship?

Answer 6

• areas of L have clouds and rain

* areas of H have fair weather High and Dry!

Question 7

What is the equatorial low also called?

Answer 7

ITCZ (Inter Tropical Convergence Zone)

Question 8

In the Inter Tropical Convergence Zone, why does air rise in the troposphere?

Answer 8

Air rises to tropopause due to intense heating (THERMAL LOW Pressure) diverges aloft and moves toward poles

Question 9

What are light winds called in the Inter Tropical Convergence Zone?

Answer 9

Doldrums

Question 10

What is the weather like in the Inter Tropical Convergence Zone?

Answer 10

Constant clouds and rain

Question 11

What is found at (20º-35º) each hemisphere?

Answer 11

Subtropical High pressure (STH)

Question 12

What happens to the air in the Subtropical High Pressure zone?

Answer 12

air aloft cools and sinks

Question 13

Why does air cool in the Subtropical High Pressure zone? Why does it sink?

Answer 13

Air Cools due to radiative heat loss into space. Heavier cool air piles up aloft and sinks

Question 14

What does cooling and sinking air create in Subtropical High Pressure zones?

Answer 14

Creates DYNAMIC High Pressure zone. Sinking air is warming = DESERTS!!!

Question 15

What are trade winds?

Answer 15

Surface air flows from STH to ITCZ, deflected to right, produces steady easterly winds, 11-13 mph

Question 16

What are prevailing westerlies? What happens to them?

Answer 16

Sinking air from STH diverges at surface and flows toward subpolar low between about 30º to 60º N & S, deflected by coriolis

Question 17

What do the westerlies produce?

Answer 17

Stormy weather

Question 18

Where are westerlie winds especially strong?

Answer 18

Winds are especially strong between 40-50° the Roaring 40s and in southern hemisphere

Question 19

What is a subpolar low also known as?

Answer 19

Also called Polar Front (“front” = where 2 air masses meet)

Question 20

What is a subpolar low (polar front)

Answer 20

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)

Question 21

What is a polar high?

Answer 21

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

Question 22

What are polar easterlies?

Answer 22

Air flows from Polar H to Polar Front (L).

Question 23

What happens to air in polar easterlies? What is it deflected by?

Answer 23

Air subsides at poles (H) and flows toward polar front (L), deflected by coriolis effect to easterly wind

Question 24

The 3-Cell is an “all water world” MODEL. Real circulation pattern is much more complicated. Why?

Answer 24

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

Question 25

What are idealized winds?

Answer 25

Idealized winds generated by pressure gradient and Coriolis Force.

Question 26

What are actual winds?

Answer 26

Actual wind patterns owing to land mass distribution.

Question 27

What are the observed patterns of pressure cells?

Answer 27

LARGE Pressure Cells

Question 28

What do continents disrupt?

Answer 28

Continents disrupt zonal (latitudinal) flow

Question 29

Why do High and Low pressure cells form?

Answer 29

H and L Pressure cells form due to land/water contrasts and surface friction

Question 30

What happens in the Southern Hemisphere?

Answer 30

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

Question 31

What is important to know about pressure and wind belts?

Answer 31

Pressure & wind belts are NOT fixed they migrate N and S as sun’s direct rays move North and South

Question 32

How many major high pressure cells are there?

Answer 32

5

Question 33

What are winds named after?

Answer 33

Winds are named from where they come!!

Question 34

What is a monsoon?

Answer 34

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)

Question 35

Where do we find monsoonal climates?

Answer 35

India and South East Asia. There is also a North American Monsoon that is in SW US and N Mexico.