ATPL Meteorology Questions

What is the dew point?

• The temperature to which air must be cooled, at constant pressure, for it to become saturated
• The temperature at which precipitation always freezes
• The altitude at which cloud base always forms
• The pressure level at which the tropopause is found

Explanation: The dew point is the temperature air must be cooled to (at constant pressure and moisture content) for it to reach saturation and condensation to begin. A small spread between air temperature and dew point suggests air close to saturation, favouring cloud or fog.

Meteorology - Temperature, Moisture & Saturation

Which weather is most typically associated with the approach of a warm front?

• Extensive medium- and low-level stratiform cloud with prolonged, steady light-to-moderate precipitation ahead of the surface front
• A narrow band of severe thunderstorms with no advance warning
• Sudden clearing with rapidly improving visibility
• Isolated afternoon showers with no organised cloud structure

Explanation: A warm front's gently sloping frontal surface tends to produce an extensive, organised sequence of cloud (typically thickening from cirrus down through altostratus to nimbostratus) with steady, prolonged precipitation well ahead of where the surface front actually crosses.

Meteorology - Air Masses & Fronts

Buys Ballot's Law, as applied in the Northern Hemisphere, states that if you stand with your back to the wind:

• Lower pressure will generally be to your left
• Lower pressure will generally be to your right
• Lower pressure will always be directly behind you
• The rule only applies in the Southern Hemisphere

Explanation: In the Northern Hemisphere, Buys Ballot's Law states that if you stand with your back to the wind, the area of lower pressure lies generally to your left - a quick rule of thumb consistent with the Coriolis-driven, counterclockwise circulation around Northern Hemisphere low-pressure systems; in the Southern Hemisphere, the relationship reverses (lower pressure to the right).

Meteorology - Pressure Systems & Wind

Turbulence in the 'rotor' zone beneath a mountain wave, compared with the smoother wave motion found aloft, tends to be:

• More violent and disorganised, occurring at lower altitude closer to the terrain
• Completely smooth, with no turbulence at all
• Only found well above the tropopause
• Identical in character to the wave motion found aloft

Explanation: Beneath the smooth, laminar wave motion found aloft downwind of a mountain range, a lower-altitude rotor zone can form with turbulent, often violent and disorganised airflow closer to the terrain - a much rougher ride than the wave itself, and a serious hazard for aircraft operating at lower levels in mountainous terrain.

Meteorology - Orographic Effects

Why do tropical revolving storms (hurricanes/typhoons) not form within about 5 degrees of latitude of the Equator?

• The Coriolis force is too weak that close to the Equator to establish and sustain the storm's rotation
• Sea surface temperatures are always too cold near the Equator
• There is insufficient moisture available in the equatorial belt
• Equatorial air is always too stable for deep convection to occur

Explanation: Tropical revolving storms depend on the Coriolis force to organise and sustain their rotary circulation. Because the Coriolis force is proportional to the sine of latitude, it becomes vanishingly small near the Equator, so the low-level convergence needed to spin up and maintain the storm's rotation cannot be established there.

Meteorology - Tropical Revolving Storms

The two air masses typically involved in the formation of a polar-front depression are:

• Polar Maritime air and Tropical Maritime air
• Polar Maritime air and Polar Continental air
• Tropical Continental air and Polar Maritime air
• Tropical Maritime air and Polar Continental air

Explanation: A classic polar-front depression forms at the boundary between cold, moist Polar Maritime air and warmer, moist Tropical Maritime air - the temperature and moisture contrast between these two air masses along the polar front provides the baroclinic energy that drives the depression's development.

Meteorology - Depression Formation

As a rule of thumb, when approaching a cumulonimbus cloud with a visible anvil top at high altitude, pilots are generally advised to keep a lateral clearance of at least how far?

• About 20 NM
• About 2 NM
• About 5 NM
• About 50 NM

Explanation: A commonly quoted rule of thumb for avoiding severe convective cells, particularly those with a well-developed anvil visible at high altitude, is to remain laterally clear by at least 20 NM, since hazardous turbulence, hail, and icing can extend well beyond the visible cloud edge, especially downwind under the anvil.

Meteorology - Thunderstorm Avoidance

In the North Atlantic, the mean position of the polar front in January (Northern Hemisphere winter) runs approximately from:

• Florida to the southwest of England
• Newfoundland to the north of Scotland
• Florida to the north of Scotland
• Newfoundland to the southwest of England

Explanation: The mean position of the polar front over the North Atlantic shifts seasonally: in the Northern Hemisphere winter (January), it lies further south and east, running roughly from the Florida area to the southwest of England, whereas in summer it retreats much further north, running roughly from Newfoundland to the north of Scotland.

Meteorology - Polar Front Position