Low Level Winds

Question 1

Anti-clockwise Movement of winds is referred to as

Answer 1

Backing

Question 2

Clockwise Movement of winds is referred to as

Answer 2

Veering

Question 3

Geostrophic winds refers to

Answer 3

PGF + Coriolis
Balanced in speed and direction
Parallel to straight isobars

Question 4

What increases the Coriolis effect force (Geostrophic force)

Answer 4

Increase in density
Faster winds
Higher latitudes

Question 5

Buys Ballot law

Answer 5

With back to wind in NH low pressure on your left
With back to wind in SH low pressure on your right

Question 6

Gradient Wind

Answer 6

PGF + Coriolis + Centrifugal force

Question 7

Gradient vs Geostrophic wind in a low pressure system

Answer 7

Geostrophic is stronger due to the opposing force on centrifugal which makes the gradient wind slower.

Gradient wind slower
Geostrophic wind faster

Question 8

Gradient Vs Geostrophic winds in high pressure

Answer 8

Gradient winds are greater than Geostrophic in high as centrifugal force act in same direction.

Gradient is faster
Geostrophic is slower

Question 9

Friction layer is

Answer 9

From SFC to 2000-3000ft
Affected by terrain etc which impacts wind and stability
At night can reduce slightly by 1000ft

Question 10

Variation in surface winds

Answer 10

Geostrophic winds above friction layer are faster
Wind speed reduces in friction layer
Coriolis reduces because wind speed is reduced in friction layer

Question 11

What happens in friction layer in NH with winds

Answer 11

Winds will back and reduce

Question 12

What will happen to winds in SH in friction layer

Answer 12

They will veer and reduce

Question 13

Figures for wind/direction change over land in friction layer

Answer 13

50% decrease in speed
25/30 degrees change in direction

Question 14

Figures for wind speed change over the ocean within friction layer

Answer 14

25/30% reduction in wind speed
Directional changes around 10/15 degrees

Question 15

Sea Breeze

Answer 15

Air over land warms and rises
Converging air creates onshore breeze
Can lead to convective cloud formation

Question 16

Land Breeze

Answer 16

Wind from land to sea over night
Weaker PGF than daytime effect

Question 17

Calm wind strength

Answer 17

Below 1kt

Question 18

Gale force wind strength

Answer 18

34kt to 47kt

Question 19

Storm force wind

Answer 19

48kt - 63kt

Question 20

Hurricane force wind

Answer 20

64kt+

Question 21

How do we measure winds

Answer 21

Anemometer (33ft AGL)

Question 22

Mountain Valley Winds on altimeter

Answer 22

Air flows down mountain and along valley
Causes altimeter to over read due to decrease in static pressure

Question 23

The Mistral Wind is (south of France)

Answer 23

A valley wind
Winds up to 70kt/strong in winter
Cold/dry northerly wind
Blows along Rhône valley
Alps create a Venturi effect

Question 24

The Boar wind is a

Answer 24

Katabatic wind
Cold/dry north easterly wind affecting the Adriatic Sea
Strongest in winter
Winds can exceed 100kt

Question 25

Foehn Winds

Answer 25

Stable air that rises up surface of mountain Cools below dew point and cools at SALR Rain and cloud on upward side and dry air on lee side Lower dewpoint on lee due to reduced vapour and warmer Referred to as a chinook in Rocky Mountains

Question 26

NE trade Winds

Answer 26

Subtropical high to ITCZ Blow Easterly

Question 27

S.E Trade Winds

Answer 27

Subtropical high to ITCZ Easterly wind

Question 28

Westerly’s - “roaring 40s”

Answer 28

Faster in south than north Higher speeds in winter season West to east

Question 29

Horse latitudes

Answer 29

Around 30N/S light winds

Question 30

Doldrums

Answer 30

Light winds at ITCZ

Question 31

Harmattan - W Africa Wind

Answer 31

NE trade wind over Africa Dry sand which impacts visibility Reduced visibility to 1000m 10-15k ft

Question 32

S America - The Pampers

Answer 32

Burst of cold air from south Blows across pampas of SA Squall lines on passage of a cold front

Question 33

Local wind systems such as katabatic winds/sea breeze/valley wind have what in common

Answer 33

Flat uniform pressure distribution

Question 34

Mountain Waves develop when

Answer 34

Wind direction is perpendicular 30 degrees Wind speed strong at least 20kt and increases with altitude Marked layer of stability/strong inversion around altitude summit