CPL Meteorology: questions asked 2021–2026

C. Mountain waves

Lens-shaped clouds that stay still over or downwind of a ridge mark the crests of standing mountain waves. Ragged edges mean turbulence.

C. CB

Showers are short, heavy bursts from convective cloud - cumulonimbus (and large cumulus). NS gives continuous rain; AC gives little or none.

B. Advection fog

Advection means horizontal movement. Warm moist air carried over colder land or sea is cooled from below to its dew point - advection fog. Radiation fog needs no movement, just a clear night.

B. Dew point

Cool air without adding or removing water vapour and at the dew point it is saturated; cool it further and the vapour condenses - dew, fog or cloud.

A. Along the rotor cloud, on the leeward side of the ridge

The rotor is a rolling eddy that forms downwind of the ridge, under the wave. The air in and along the rotor cloud is violently turbulent, like the inside of a thunderstorm. Treat the whole rotor zone on the lee side as a no-go area.

C. Upper stratosphere

Nacreous (mother-of-pearl) clouds are thin iridescent clouds in the stratosphere, around 20-30 km, seen mostly in high latitudes. Do not confuse them with noctilucent clouds, which are higher still, in the mesosphere.

B. 1.25 m

In India the thermometers sit in a Stevenson screen with the bulbs 1.25 m above the ground - high enough to avoid the extreme ground temperature, shaded from direct sun and rain, and ventilated by louvres.

B. Stratus

Drizzle is fine droplets from a shallow, low layer cloud - stratus (or thin stratocumulus). The cloud is too shallow for drops to grow big.

B. Inversion

Temperature rising with height is an inversion - a negative lapse rate. It is the most stable arrangement the atmosphere can have.

B. Backs and decreases

Friction slows the surface wind; a slower wind has less Coriolis force, so the pressure gradient turns it towards low pressure. In the NH that is a backing. Climbing out of the friction layer (to about 2000 ft), the wind veers and strengthens.

C. Cumulonimbus

Only the cumulonimbus has the updraughts to grow hail. It is also the cloud of heavy showers, lightning, severe icing and turbulence.

B. Afternoon

Surface heating builds through the day, so convection and showers over land peak in the afternoon.

B. Below 1000 m

FG is reported when water droplets reduce the visibility to less than 1000 m. From 1000 m up to 5000 m with humid air it is mist (BR).

A. Less than 4 km

A microburst is a violent downburst less than 4 km across, lasting only a few minutes - small enough to catch an aircraft on final approach.

B. 4 km or more

A downburst 4 km or more across is a macroburst; under 4 km it is a microburst.