Meteorology and the Atmosphere
This domain tests atmospheric structure and composition, humidity, stability, cloud formation, pressure systems, fronts, severe weather, and climate versus weather. Expect interpretation of lapse rates and dew points.
Core rules and concepts
- The troposphere contains most weather; temperature generally decreases with altitude until the stratosphere, where ozone absorbs UV.
- Relative humidity depends on temperature: warming air without adding vapor lowers relative humidity.
- Unsaturated air cools at about 10°C/km (dry adiabatic rate); saturated air cools more slowly because condensation releases latent heat.
- Clouds form when air cools to its dew point, often by lifting along fronts, mountains, or convection.
- Low pressure is associated with converging, rising air and clouds; high pressure with sinking, drying air.
- Cold fronts produce steep lifting and often intense, short storms; warm fronts produce gentler, widespread precipitation.
Worked example
Surface air is 25°C with a dew point of 13°C. The dry adiabatic rate is about 10°C/km, and the dew point decreases about 2°C/km. The temperature-dew point difference is 12°C, and it closes at about 8°C/km, so condensation occurs near 12 ÷ 8 = 1.5 km. That height is the approximate cloud base.
Traps that cost marks
- Confusing relative humidity with absolute moisture content.
- Saying high pressure causes storms; high pressure favors sinking air and clearing.
- Reversing cold- and warm-front precipitation patterns.
- Treating weather and climate as synonyms; climate is long-term statistical pattern.