ATPL Wind

Question 1

Describe the basic concept of the coriolis force formula and what each thing means.

Horizontal CF= 2ΩvsinΦ

Answer 1

Ω= earths angular velocity
v = speed of wind
SinΦ = sin of latitude

Question 2

Describe the development of the geostrophic wind balance in both hemispheres

Answer 2

It is the balance of the Coriolis and pressure gradient force.

When air starts moving CF starts effecting it, deflection increases until CF balances PGF, isobars are straight and wind is parallel to the isobars.

CF acts to right angles and deflects wind to the left in SH and right for NH

Question 3

Describe development of gradient wind balance in both hemispheres.

Answer 3

IF CF is greater the wind will be anticylonic

If PG is greater the wind will be cyclonic.

Question 4

Given equal spacing between isobars explain why wind speed is stronger around a high than around a depression.

Answer 4

CF dominates the high and CF is proportional to wind speed whereas PGF dominates the low as lowest pressure is in the centre and high goes to low so with less CF theres less wind speed

Question 5

Demonstrate the effects of friction on surface wind.

Answer 5

Friction layer surface to 2000 – 3000ft

•Friction reduces wind speed
•Reduced wind speed reduces Coriolis force
•Pressure gradient force strongest, wind veers towards low in southern hemisphere or backs towards low in northern hemisphere

Question 6

Describe diurnal variation of surface wind on SH and NH

Answer 6

SH = increases/backs during the day, decreases/veers at night

NH = increases/veers during the day, decreases/backs at night

Question 7

State the change in wind velocity when climbing out of or descending into the friction layer.

Answer 7

SH climbing = ABI (ascend, back, increase)
•SH descending = DVD (descend, veer, decrease)
•NH climbing = AVI
•NH descending = DBD