Chapter 17: Wind (PP ch 10)

Question 1

Wind Measurement

Device Velocity, Direction, Recording?

Answer 1

Anemometer (10 m AGL)
Wind Vane
Anemograph

Question 2

Wind Strength (4)

Answer 2

Calm < 1 kn
Gale 34 - 47 kn
Storm 48 - 63 kn
Hurricane > 64 kn

Question 3

Wind Temporary Changes (3)

Answer 3

Gust: + 10 kn < 1 min
Squall: + 10 kn > 1 min
Lull: drop in wind

Question 4

Wind Reporting

ATIS vs Charts? Wind Direction Change (2)

Answer 4

ATIS: magnetic (same as RW)
Charts: true
Veering: clockwise
Backing: counter clockwise

Question 5

Coriolis Force

Equation? Strongest at?

Answer 5

CF = 2 Ω ρ V sin(θ)

Strongest at Poles (largest change in diameter per degree of lattitude)

Question 6

Coriolis Force

Wind Turn Direction?

Answer 6

N. Hem: wind turns right

S. Hem: wind turns left

Question 7

Coriolis Force

Name of Wind (2)

Answer 7

Geostrophic: straight Isobar

Wind Gradient: curved Isobar

Question 8

Surface Wind

Layers (2)

Answer 8

Smooth laminar airflow (undisturbed)
Friction layer (disturbed by buildings, heat...)
   warmer = faster because mixing with laminar flow

Question 9

Wind Direction /Amplitude Change With Surface

Low P, High P?

Answer 9

Sea - 10° - 75%
Land - 30° - 50%
Land night - 45° - 25%
Low Pressure -> inside
High Pressure -> outside

Question 10

Coriolis Force Increase

What effect on windspeed?

Answer 10

Decrease wind speed

high coriolis reduces wind pressure gradient

Question 11

Local Winds at Coast (2)

Name, wind speeds, distance, info

Answer 11

Sea breeze - 10 kn, 10 - 15 nmi (Europe)

Land breeze - 5 kn, 5 nmi, veers when V increases (hot)

Question 12

Local Winds Topographical (5)

Info

Answer 12

Anabatic - surface heat -> air flows upwards out of valley. Later afternoon airflow in valley
Katabatic - cool air -> air flows downwards into valley. Night airflow in valley
Mechanical Friction - turbulence lee side
Mountain Waves
Topographical Windshear - turbulence due to obstacles

Question 13

Mountain Waves

Requirements (4), Height, Dimensions in Famous Mountain Chains (3), TEM (3)

Answer 13

Increasing wind intensity with alt
15 - 20 kn wind @ 90°
Layer of stable and unstable air lee side
Height 1500' 
Penines 250 nmi Rockies 300 Andes 500
TEM: updraughts (600 ft/min = severe)
Turbulent up to tropopause
Rotor clouds (looping air)

Question 14

Global Wind Patterns (4)

What is at ITCZ

Answer 14

NE Trade routes, SE Trade routes (going west)
Westerlies (east)
Polar Easterlies (west)
ITCZ: doldrums (still, calm conditions)

Question 15

Specific Local Winds

Answer 15

Bora: cold, high P Alpine air into Adriatic Sea (100 kn)
Mistral: Rhone Valley wind through alps (40 - 70kn)
Harmattan: NE trade wind in N. Africa. Dust storms. Vis affected up to 3000’, height of 10 - 15000’
Pampero: Polar air from mid lattitude lows, strongest in summer (oct - jan)