Dynamics 2

Question 1

What are the three different types of meridional circulations?

Answer 1

Hadley Cell (important)
- hot air rises in the inter-tropical convergence zone (ITCZ) due to shortwave absorption, sensible and latent heating, spreads poleward and cools by longwave emission and sinks over the sub-tropical high

Ferrel Cell
- warm subtropical air moves poleward, rises over cold polar air at polar front and spreads equatorward in the upper atmosphere

Polar Cell
- surface cold-air outbreaks

Question 2

What are the distribution of surface winds?

Answer 2

Tropics - low pressure, inflows of air from the subtropic at lower atmosphere. Air rises and diverges to the subtropics

Subtropics - high pressure, air converges in the upper atmosphere and sinks towards the lower atmosphere. Outflow of air in the lower atmosphere towards the tropics and the polar fronts

Question 3

What is the Coriolis Effect?

Answer 3

The deflection of winds that is caused by the Earth’s rotation. Namely, the Earth rotates faster at the equator than at higher latitudes.

• Wind bends towards the right in the Northern Hemisphere
• Wind bends towards the left in the Southern Hemisphere

Question 4

(Zonal Winds)

What are trade winds?

What are moonsoons?

Answer 4

Trade winds are winds the blow from east to west at the equator. They are caused by the Coriolis effect.

Monsoons are winds that blow in one direction for half a year and in the opposite direction for the other half of the year. They are caused by unequal heating of continents and oceans. (usually refers to Asian monsoon)

Question 5

(Zonal Winds)

What is the Walker Circulation?

What is the ENSO?

Answer 5

• east-west atmospheric circulation along the equator
• over the pacific ocean
• undergoes interannual oscillations known as the El-Nino Southern Oscillation (ENSO)

La-Nina

• high pressure air from Tahiti flows to low pressure air in Australia
• low pressure air in Australia caused by strong uplifting and evaporation from the indo-Pacific warm pool
• droughts in Peru and Chile

El-Nino:

• High pressure air from Australia flows towards Tahiti
• draughts in Papua New Guinea and Eastern Indonesia

Question 6

(Zonal Winds)

What are the cyclones formed at the mid-latitudes and the polar front?

Answer 6

Anti-cyclones:

• usually formed closer to the poles
• cold air moves equatorwards and downwards
• surface wind spins outwards
• rotates clockwise in the North (anti-clockwise in the South)

Cyclones:

• usually formed closer to the mid-latitudes
• warm air moves polewards and upwards
• surface wind spins inwards
• rotates anti-clockwise in the North (clockwise in the South)