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Flashcards in chapter 7: Jet and Jet streaks Deck (29)
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1

Weather processes strongly depend on

the structure and dynamics of jet streams

2

There are ......................major ........................jet streams in the upper ...........................in each hemisphere

two

westerly

troposphere

3

There are two major westerly jet streams in the upper troposphere in each hemisphere

– Polar jet stream
– Subtropical jet stream

4

The structure of jet streams are related to

temperature distribution through the thermal wind relationship

5

Warm air to the south results in

westerly geostrophic winds through the thermal wind relationship.

6

Draw the jet stream (box)

7

The thermal wind relationship also explains why

the jet stream tends to be collocated with the polar front.

8

Large horizontal temperature gradients >     >       >

large horizontal temperature gradients 

Large thickness gradients>

Large horizontal pressure gradient aloft>

strong winds

9

The polar jet is the band of

(speed ) (found in)

meandering strong winds (~100 knots) found at the tropopause.

10

The polar jet moves

meridionally (30°-60° latitude) and vertically (10-15 km) with the seasons.

11

Large vertical extent: maximum usually near .................... but can be seen at ...................

300 mb 

200mb - 500mb

12

At times, the polar jet will split into ..................................and possibly merge with .............................

northern and southern branches

the subtropical jet

13

Polar Jet and thermal wind balance:

it is associated with:

strong quasi-horizontal temperature gradients in the lower troposphere and strong vertical wind shear.

14

It is associated with strong quasi-horizontal temperature gradients in the lower troposphere and strong vertical wind shear.

• These features are often associated with

the polar front.

15

Meridional undulations of the jet stream are associated with

poleward and equatorward displacements of warm and cold air, respectively.

16

The subtropical jet is associated with........................................... between........................... usually found between.........................

subtropical front between the tropical and mid-latitude air masses and is usually found between 25° and 30° N.

17

It meanders less than..............................., but in rare cases has been observed as far..............................

the polar jet

north as 60°N

18

Subtropical jet is ...........................

shallow

19

subtropical jet stream is rather shallow – sometimes less than ...................................and may not show up on...................................

3 km in depth

either of the 200 mb or 300 mb standard levels

20

Subtropical Jet Stream directly influences ................................

low-level flow only when it becomes coupled through deep cumulus convection and interactions with the polar jet

21

what are the two cases that subtropical jet streams affect low:

  1. when it becomes coupled through deep cumulus convection and
  2. interactions with the polar jet

22

Like the Polar-Front jet, the subtropical jet is associated with a

change in height of the tropopause.

23

The meridional temperature gradient associated with the

vertical shear under the subtropical jet is concentrated in a shallow layer

24

Sometimes the subtropical jet is associated with a

a portion of the Polar-Front jet that has migrated equatorward into the subtropics and has lost its low-level baroclinicity.

25

define Barcoclinicity

surfaces of pressure intercect surfaces of temperature and density (occure at fronts)

FRONT HAS BAROCLINITY

26

Subtropical Jet position is ................. than polar jet

higher

27

subtropical jets and polar jet separate ........

cells

28

The presence of the subtropical jet relates to the

conservation of absolute angular momentum in the context of the Hadley cell.

29