Weather, Climate and Atmosphere
What this domain tests
This domain examines the atmosphere's structure and how energy, pressure and moisture produce weather and climate. Expect climate-graph interpretation, pressure-system diagrams and explanations of climate change.
Core rules and concepts
- The troposphere contains most weather; temperature generally falls with altitude at the environmental lapse rate (about 6.5°C per 1,000 m).
- Insolation varies with latitude, season and surface albedo. Low latitudes receive more concentrated energy; high latitudes receive it at a lower angle over a larger area.
- Air moves from high to low pressure. The Coriolis effect deflects it: right in the Northern Hemisphere, left in the Southern.
- Cloud forms when air cools to its dew point, usually by forced ascent over relief, frontal uplift or convection.
- Climate controls include latitude, altitude, distance from the sea, ocean currents, prevailing winds and relief.
- Climate graphs show mean monthly temperature (line) and rainfall (bars). Temperature range = warmest month minus coldest month.
Worked example
A climate graph shows a maximum of 22°C in July, a minimum of 4°C in January and total rainfall of 620 mm. Reasoning: range = 22 − 4 = 18°C. The July peak indicates the Northern Hemisphere. 620 mm is moderate, not desert (<250 mm) or rainforest (>2,000 mm). State the values before interpreting, so the examiner sees your method.
Traps that cost marks
- Treating weather (short-term) and climate (long-term average) as synonyms.
- Reading the rainfall bars against the temperature axis, or omitting units.
- Saying 'hot air rises because it is light' without explaining density and pressure.
- Ignoring the difference between the environmental lapse rate and the adiabatic rate.