Anti Cyclones (high)

Question 1

Describe formation process of anticyclones

Answer 1

Air flowing from equator at tropopause height collides with air traveling from poles and descends
•Creates warm subtropical highs/anticyclones
•Air at the poles cools increasing density and draws more air down
•Creates cold polar highs/anticyclones

Question 2

Describe anticyclones, pressure patterns and wind flow

Answer 2

•Rotates anticlockwise in southern hemisphere
•Rotates clockwise in northern hemisphere
•Isobars widely spaced at centre then closer further out
•Wind flows parallel to the isobars
•Lower level divergence upper level convergence

Question 3

Describe anticyclones (highs) with reference to subsidence and subsidence inversions

Answer 3

•Subsidence = vertical downdraft of air
•Pressure increases as air subsides
•Heated adiabatically at DALR
•Subsiding air will be warmer than surrounding air creating inversion

Question 4

Describe anticyclones (highs) with reference to typical associated weather conditions

Answer 4

Summer = no cloud, light winds and haze

Winter = extensive stratus with low base and limited vertical extent. Also has fog, drizzle and light winds

Question 5

Describe the development of ‘cold’ highs

Answer 5

•White ice/snow has high albedo and reflects insolation

•Surface stays cold and cools first 10cm through conduction

•Turbulence mixes air up to 5,000ft and then condenses

•Can occur over any large cold area but permanent at the poles

Question 6

Discuss hazards associated with anticyclones

Answer 6

Low level cloud can force aircraft down lower
•Haze reduces visibility
•Fog can block runways