FAA Part 107 Remote Pilot (UAG)WeatherMedium
On a clear, calm night, a remote pilot notes that surface temperatures have dropped sharply while temperatures several hundred feet above the ground remain much warmer, trapping smoke and haze near the surface. This condition is best described as what type of inversion?
- ASubsidence inversion
- BFrontal inversion
- CRadiation (surface-based) inversion
- DTurbulence inversion
Show answer & explanationAnswer & explanation
Correct answer: C. Radiation (surface-based) inversion
A radiation inversion forms on clear, calm nights as the ground rapidly radiates heat away, cooling the surface air faster than the air above it. This creates a stable, shallow layer near the surface that traps smoke, haze, and moisture, often reducing visibility for early morning sUAS operations.
Why the other options are wrong
- A. A subsidence inversion is caused by sinking air in a high-pressure system, typically aloft, not from nighttime surface cooling.
- B. A frontal inversion occurs when warm air overrides cold air along a frontal surface, not from surface radiational cooling.
- D. A turbulence inversion forms from mixing that traps warmer air above a cooler mixed layer, unrelated to radiational cooling.
Radiation (Surface) Inversion
A temperature inversion that forms near the ground on clear, calm nights as the surface cools faster than the air above it.
- Requires clear skies and light/calm winds
- Most pronounced just before sunrise
- Traps fog, haze, smoke, and pollutants near the surface
- Typically dissipates after sunrise as surface heating resumes
Memory trick: 'Radiation inversion = night's cold blanket' hugging the ground.