Meteorology
The atmosphere and pressure
Know the standard atmosphere and how pressure, temperature and density change with altitude. Understand how pressure systems drive wind: air flows from high to low pressure, deflected by Coriolis force, giving geostrophic wind aloft and friction-modified wind at the surface. A frequent trap is the relationship between wind and isobars - the closer the isobars, the stronger the wind.
Stability, clouds and precipitation
Distinguish stable from unstable air by lapse rate and by cloud type: stratiform clouds indicate stability, cumuliform clouds indicate instability. Know the cloud families and the conditions that produce thunderstorms. Convective storms require moisture, instability and a lifting mechanism; they pass through cumulus, mature and dissipating stages, and the mature stage brings the greatest hazard - hail, severe turbulence, microbursts and lightning. A classic question asks which stage is most dangerous: the mature stage.
Icing and visibility
Structural icing requires visible moisture and temperatures near or below freezing; clear ice forms in large supercooled droplets, rime ice in small ones. Know that freezing rain indicates a warm layer aloft and severe icing risk. Fog forms by cooling or by adding moisture; radiation fog appears on clear, calm nights and usually dissipates after sunrise.
Worked rule of thumb
To estimate the height of a cumulus base, use the spread between temperature and dew point: roughly 125 m of cloud base per 1 °C of spread. A spread of 8 °C gives about 1000 m. This is approximate and must be checked against local conditions, but it is a reliable exam shortcut.
Local phenomena
Understand mountain waves, sea breezes, valley winds and the effect of terrain on turbulence. In Brazil, know the seasonal behaviour of the ITCZ and the passage of frontal systems.