Meteorology and the Atmosphere
Meteorology and the Atmosphere
This domain tests atmospheric structure and composition, energy transfer, humidity, stability, clouds, air masses and fronts, severe weather, global circulation, and climate.
Core concepts
- The troposphere contains most weather and cools with altitude. The stratosphere warms with altitude because ozone absorbs ultraviolet radiation. Pressure decreases with altitude.
- Relative humidity compares actual vapor pressure with saturation vapor pressure. Cooling air to its dew point causes condensation and cloud formation.
- Lapse rates: environmental lapse rate (ELR), dry adiabatic rate about 10°C/km, and saturated adiabatic rate about 6°C/km.
- Stability depends on parcel versus environment temperature. If ELR > dry adiabatic rate, the atmosphere is absolutely unstable; if ELR < saturated adiabatic rate, absolutely stable; between them, conditionally unstable.
- Air masses are cP, cT, mP, and mT. Fronts include cold, warm, occluded, and stationary. Midlatitude cyclones, thunderstorms, tornadoes, and hurricanes have distinct formation requirements.
- Global circulation consists of Hadley, Ferrel, and polar cells, producing trade winds, westerlies, and polar easterlies.
Worked example
A parcel rises 1 km with an ELR of 9°C/km and a dry adiabatic rate of 10°C/km. The parcel cools 10°C, while the environment cools 9°C. The parcel becomes 1°C colder than its surroundings, so it is denser and sinks back: the layer is stable. Reasoning: compare parcel temperature with environmental temperature at the same height.
Traps
Surface high pressure means sinking air and fair weather; low pressure means rising air and clouds. Relative humidity can fall as air warms even if vapor content is unchanged. Dew point is a temperature, not a humidity percentage. The Coriolis effect is zero at the equator. Hurricanes require warm water and low wind shear, not just thunderstorms.