Upper Level Winds Flashcards
(20 cards)
How do upper winds occur
TEMP difference creates a PRESSURE difference
What direction are the winds in both hemispheres
WESTERLY at altitudes in the troposphere
What is different in the stratosphere to do with temp
It is colder at the equator and less cold at the poles
Opposite
What happens to winds at the equator during summer
They could be easterly over India or Africa
What is a Jet Stream
A strong narrow current characterised by strong vertical or lateral wind shears where wind speed must exceed 60kt
Why do jet streams occur at the polar tropopause and tropical tropopause boundaries
Because there is a steeper temperature gradient at these points
What is normally the strongest jet stream
The polar front jet
What are the two main jet streams
Polar front
Sub tropical
What are the typical jet streams dimensions
2nm / 2000ft tall
200nm wide
1500nm + long
What is the ratio or width to height of a jet stream
100 : 1
What is the
Minimum
Typical
Less frequent
Rare
Speeds of a jet stream
61-80kt
100-150 kt
150 - 200 kt
More than 200kt
What is the difference in earths spinning speeds at the equator and 30 latitude
Equator is 900kt
30 latitude 780 kt
Due to coriolis effect
What air is the core of the jet stream
Warm air
Where do jet streams form
The warmer air below the tropopause
Approximate figures to remember for different JS
Artic front, 20000ft, lat 60
Polar front, 30000ft, lat 50
Sub tropical, 40000ft, lat 40
Equitorial easterly, 45000ft, lat 10
How could low level jets occur
Due to nocturnal radiation and temp inversion in mountainous areas which shield the jet from surface friction
They could be as low as 5000ft
What do low level js produce
Extreme wind Shear and turbulence and are associated with barriers and surface inversions
