Upper Level Winds and Jet Stream Flashcards
Define Jet Stream
A jet stream is a relatively narrow, rapidly flowing, ribbon-like stream of air embedded in main air flow.
How long, thick and wide is a jet stream?
Thousands of miles long, a few thousand feet thick and a few hundred feet wide.
How fast must a jet stream be?
At least 60 kts.
How do jet streams develop?
When there is a strong horizontal temperature gradient through a deep layer of the atmosphere.
________ temperature differences cause wind speeds to increase with height.
Horizontal
True of False: The stronger the horizontal temperature difference, the greater the increase in wind speed aloft.
True
Isotherms run approximately is what direction?
West to East
Do upper level winds blow parallel or perpendicular to isotherms?
Parallel
_____ is more dense than _____ air.
Cold / Warm
Does pressure increase or decrease more rapidly with height in cold air?
Decreases more rapidly.
The _____ the horizontal temperature gradients, the greater the increase of wind speed with height.
Stronger
Consider a pressure surface between warm and cold air. Towards which does the surface slope?
Cold surface
Horizontal temperature causes a large slope in upper pressure surfaces. Does this result in a strong or weak PFG?
Really strong.
Wind becomes parallel and much stronger North or South or the front?
North
Which of the following jets is the highest, lowest and in-between in altitude Maritime, Arctic and Polar jet?
Highest: Polar
In-between: Maritime
Lowest: Arctic
True or false?
Jets will never merge into 2 or even 1 wider jet.
False
Define Jet Axis
Strongest winds at a particular level. Ex. 250hPa
Jet Core
The jet axis where the wind speed is maximum.
Jet Maximum
A point along the axis where the wind speed is at a maximum.
Which side along a surface front does a jet stream exist?
Poleward side
True or False?
The jet stream is in the colder air mass.
False, it is in the warm air mass.
True or False?
Jet streams are positioned above the tropopause.
False, they exist below it.
Jet streams are associated with which type of cloud?
Cirrus
Which edge, either cold or warm, is the jet stream near in a cirrus cloud deck?
Cold edge
Which side of the jet is the cirrus cloud deck on, warm or cold?
Warm
Does the wind increase or decrease away from the jet?
Decreases
True or False?
Horizontal wind shears are stronger than vertical around the jet.
False
Is there a difference in HWS on the cold and warm side of the jet? if so, which one is stronger and by how much.
Yes, the cold air side is 3X stronger.
In winter, temperature contrasts between air masses is stronger or weaker?
Stronger
The tilt of the North Pole away from the sun in winter does what to the following regarding jets:
Latitude
Height
Wind Speed
No. of Jets
Moves further south
Lowers
Stronger
3 instead of 2
Are thermal winds stronger in winter or summer?
Winter
What are the two types of Non-Frontal jet streams?
Arctic Stratospheric & Subtropical
Solar heating at the equator causes which non-frontal jet stream?
Subtropical
True or False?
Both non-frontal jet streams are westerly
True
Which non-frontal jet stream is higher?
Arctic Jet Stream
