Lecture 10: Prevailing Winds and Upper-level Circulation

Question 1

Main circulation patterns

Hadley cell

Answer 1

a large scale convection cell in which air rises at the equator and sinks at medium latitudes, 30 degrees N or S
circulation in the tropics (northeast and southeast trade winds)

Why: rising air aloft flows toward poles, decends near subtropics

Question 2

Main circulation patterns

Polar cell

Answer 2

converges with air from south, forcing air to rise forming subpolar lows, circulation in the high latitudes

Question 3

Main circulation patterns

Farrell cell

Answer 3

cell that moves air from 30 degrees to 60 degrees latitude, circulation in the mid-latitudes (westerlies)

Why: air moves away from subtropical high and links subtropical H and subpolar L

Question 4

How and why does the ITCZ migrate throughout the year?

Answer 4

How far from the equator it gets is largely determined by the land or ocean temperatures underneath the currents of air and moisture. Otter oceans yield less volatile change while varying lands cause varying degrees in its location

Question 5

How does air circulate aloft in the mid-latitudes, tropics and poles?

Answer 5

The rising motion of air along with the sinking next to the Hadley cell would set up upper level circulation over the mid-latitudes, with air moving from the poles toward the tropics

Question 6

What/where is the Polar Front Jet Stream and what do Rossby waves mean for weather in the U.S?

Answer 6

Jet streams are narrow currents of fast-moving winds and the polar front jet stream is 45-60 degrees N. Rossby waves are associated with the polar front jet stream and separates cold polar air from warm tropical air

Question 7

How and why does tropopause height change with latitude and why does this matter?

Answer 7

The height drops in the area of the subtropical and polar front jet stream causing movement of the frontal low (at the surface) into the cold air mass

Question 8

ITCZ

Answer 8

belt of low pressure around the equator formed by the vertical ascent of warm air from the latitudes N and S of equator

Question 9

Jet stream

Answer 9

a narrow belt of strong winds that blow in the upper troposphere

Question 10

Polar front jet stream

Answer 10

rivers of high speed air in the upper atmosphere that flows along the polar front

Question 11

Rossby waves

Answer 11

develop in the polar front jet stream when significant temperature differences exist between tropical and polar air masses

Question 12

Ridges/troughs

Answer 12

elongated zones of high and low pressure

Question 13

Trough

Answer 13

Bends away from pole

Question 14

Ridge

Answer 14

Bends towards pole

Question 15

Polar easterlies

Answer 15

prevailing winds that blow from east to west

Between 60-90 degrees latitude in both hemispheres

Question 16

Westerlies

Answer 16

dominant winds of the mid-latitudes that move from the subtropical highs to the subpolar lows from E to W