China Civil UAV Theory Questions — Questions 541–550

Mid-level clouds are below 0°C, thick, and water-rich, so icing is most severe there. Option A is wrong (high clouds can also ice); option C is wrong (low clouds may contain supercooled droplets).

Ice shapes are generally divided into groove ice, wedge ice, and mixed ice.

After leaving its source region, an air mass changes properties under the influence of the underlying surface (modification). Option A is wrong (China cannot generate every type of air mass); option C is wrong (air masses form in many regions).

Study note: when you see the underlying surface, choose it. Air mass modification mainly occurs when an air mass moves over an underlying surface of different properties, exchanging heat and moisture with it.

The horizontal pressure gradient force drives air from high to low pressure; the Coriolis force acts perpendicular to motion (deflecting to the right in the Northern Hemisphere), preventing air from flowing directly toward low pressure.

The horizontal pressure gradient force, caused by pressure differences, is the original driving force of wind, pushing air from high to low pressure.

Convective clouds (such as cumulonimbus) bring strong convection, lightning, and other severe weather, posing the greatest hazard to takeoff and landing.

Minimum visibility is the smallest visible distance when visibility varies by direction.

A high dew point means more water vapor; a low dew point means less water vapor, so dew point indicates water vapor content.

The lower troposphere (below 1500 m) is strongly affected by terrain and surface friction, with chaotic airflow; the upper layer is little affected by the surface. The wind direction difference is mainly due to ground friction.