Soaring Weather and Meteorology Flashcards

Which of the following atmospheric conditions is most conducive to the formation of strong mountain wave lift suitable for soaring?

Answer: A stable air mass with wind speed of at least 15-25 knots at the summit, increasing with altitude, and blowing within 30 degrees perpendicular to the ridge.

Strong mountain wave lift requires three key ingredients: a stable air mass, significant wind speed at ridge-top level (at least 15-25 knots), and a wind direction that is roughly perpendicular to the mountain range. [2, 6, 10] The stability prevents air from rising in thermals and instead forces it to oscillate in a wave pattern after flowing over the mountain. The wind must be strong enough to create the wave and should ideally increase with altitude to sustain the wave's energy. [2, 3, 6] Unstable air, decreasing wind speed, parallel winds, or light/variable winds are all detrimental to wave formation. [2]

A glider pilot is flying near the coast on a warm, sunny day with light general winds. They notice a line of small cumulus clouds forming a few miles inland, parallel to the coastline. This visual cue most likely indicates the presence of:

Answer: A sea breeze front with potential for soarable lift.

On a warm, sunny day with light prevailing winds, the land heats up faster than the adjacent sea. This creates a pressure difference, causing cooler, denser air from the sea to move inland. This leading edge of cool air is called a sea breeze front. [1, 36] As it pushes the warmer, moist inland air upward, it often triggers condensation and forms a line of cumulus clouds, which marks a line of potential lift for soaring. [1, 33]

An atmospheric sounding indicates a steep lapse rate, where the temperature decreases rapidly with altitude (more than 3°C per 1,000 feet). This condition is described as:

Answer: Unstable, and favorable for thermal development.

An unstable atmosphere is characterized by a steep lapse rate, meaning the temperature drops quickly with an increase in altitude. [7, 16, 32] When a parcel of air near the surface is heated, it becomes warmer (and less dense) than the surrounding air and begins to rise. [35] In an unstable environment, this rising parcel will remain warmer than the surrounding air as it ascends, causing it to continue accelerating upward, thus forming strong thermals suitable for soaring. [7, 8, 32] A stable atmosphere or an inversion would suppress this vertical motion. [28, 35]

When utilizing ridge lift, what is the correct procedure for making turns while flying below the crest of the ridge?

Answer: All turns should be made away from the ridge.

For safety, when flying below the crest of a ridge, all turns should be made away from the rising terrain. [23] Turning towards the ridge significantly reduces the margin for error, increases the risk of collision with the terrain, and can place the glider in the sink on the downwind side of the turn. Turning away from the ridge ensures the glider moves into an area with more clearance and provides a clear escape route if lift weakens or unexpected sink is encountered. [23]

A pilot is planning a cross-country thermal flight. Which weather characteristic would be MOST detrimental to a successful soaring day?

Answer: A high-pressure system with a strong capping inversion at a low altitude.

A strong capping inversion at a low altitude acts like a lid on the atmosphere, preventing warm air parcels (thermals) from rising very high. [11, 12] Even if the sun heats the ground effectively, the thermals will be stopped by this stable layer, resulting in weak, short-lived lift and making it impossible to gain significant altitude for a cross-country flight. The other options are generally favorable: scattered cumulus clouds mark thermals, increasing wind can help organize thermals into streets, and a dry adiabatic lapse rate indicates instability needed for thermals to form. [11, 15, 31]

Which of the following is a primary hazard associated with flying in the rotor zone of a mountain wave system?

Answer: Severe to extreme turbulence and strong downdrafts.

The rotor is an area of extreme turbulence that forms at low altitudes on the lee side of a mountain, underneath the primary wave crests. [3, 10] It is characterized by chaotic, rotating air masses that can produce severe to extreme turbulence, strong updrafts, and powerful downdrafts, posing a significant structural and control hazard to any aircraft, especially gliders. [3, 10] The air in the rotor is anything but smooth.