China Civil UAV Theory Questions — Questions 551–560

Land and sea have different heat capacities; land absorbs and releases heat faster than water. During the day, land warms fast, air rises, and sea breeze flows in to replace it; at night the reverse forms land breeze.

Relative humidity is the percentage of water vapor pressure to saturation vapor pressure in the air.

Water vapor comes mainly from surface evaporation, so air near the ground holds more of it; with increasing height, vapor sources decrease and vapor content falls. Vertical air motion carries vapor upward, but falling temperatures condense it into droplets or ice crystals, further reducing vapor content. Also, as height increases, atmospheric pressure falls, and lower pressure air can hold less vapor.

Force 4 wind speed is 5.5–7.9 m/s, a fixed fact to memorize.

When cold and warm air masses are evenly matched, their boundary hardly moves; this front is called a stationary front (such as the Jiangnan rainy season).

Tropospheric temperature decreases with increasing height, so “temperature rises with height” is wrong; options B and C are tropospheric characteristics.

Atmospheric weight at 18,000 feet is about half that at sea level, a fixed fact to memorize.

A front is where cold and warm air meet, with complex airflow; a fast-moving cold front can produce strong near-ground wind shear, a major flight safety threat.

Icing intensity is divided into light, moderate, and severe, each corresponding to different hazard levels and responses.

Wind direction 270 degrees is a west wind; heading 90 degrees is due east, so the aircraft flies with the wind: tailwind flight.