China Civil UAV Theory Questions — Questions 571–580

On significant weather forecast charts, a scalloped area outlined by a black dashed line indicates a clear-air turbulence zone, with top and base heights marked.

In stable air, vertical motion is suppressed, water vapor does not easily rise and condense, and visibility is excellent. Options B and C are unstable atmosphere characteristics.

Absolute zero is 0 K, equal to −273°C.

Study note: for valley winds, look at the valley. During the day, mountain slopes warm fast, air rises, valley air flows in to replace it, and wind blows from the valley toward the slope (valley wind); valley winds are thermal circulations formed by terrain temperature differences.

The higher the temperature, the more water vapor air can hold (saturation vapor pressure rises with temperature).

After a fast-moving cold front, the cold air mass takes control, pressure rises, the atmosphere stabilizes, and skies clear quickly.

With greater density, lift and drag increase (greater aerodynamic force on the aircraft), and engines take in more air, increasing thrust.

Lower pressure means lower air density, less lift and drag, requiring higher takeoff and landing speeds and longer distances; engine thrust weakens, reducing climb rate.

Study note: when you see 0.65, choose 0.65. For every 100 meters of altitude gain, air temperature drops 0.65°C. By elimination: at 6.5°C/100 m, high-altitude temperatures would be unrealistically low.

Study note: when you see 0.65, choose 0.65. For every 100 meters of altitude gain, air temperature drops 0.65°C; this is the tropospheric average lapse rate.