Atmosphere: Weather, Climate and Atmospheric Circulation
What this domain tests
This domain examines atmospheric composition and structure, insolation and temperature, pressure belts, planetary and local winds, and the monsoon system.
Core rules
- Dry air is about 78% nitrogen, 21% oxygen, 0.93% argon and 0.04% carbon dioxide. Water vapour varies.
- Layers: troposphere (weather), stratosphere (ozone layer), mesosphere, thermosphere. Normal lapse rate is about 6.5°C per km in the troposphere.
- Pressure belts: equatorial low, subtropical high, subpolar low, polar high. The Coriolis force is zero at the equator and maximum at the poles.
- Planetary winds: trade winds blow from subtropical highs toward the equator; westerlies from subtropical highs toward subpolar lows; polar easterlies from polar highs.
Worked example
Why do trade winds in the Northern Hemisphere blow from the northeast? Air moves from the subtropical high near 30°N toward the equatorial low. As it moves southward, the Coriolis force deflects it to the right of its path. Rightward deflection turns southward flow into a wind from the northeast, hence northeast trades.
Traps
A sea breeze blows from sea to land by day; a land breeze blows from land to sea at night. The ITCZ shifts with the sun and is not fixed at the equator. Monsoon is a seasonal reversal, not simply a strong sea breeze. Jet streams are upper-air westerlies, not surface trade winds.