Extreme cold and turbulence over Korea

The bitter cold that has lingered across central South Korea, with morning lows around minus 10 degrees Celsius and daytime temperatures remaining below freezing, has far-reaching implications. As the cold tightens its grip at the surface, it also affects the atmosphere above, making aircraft flying over the Korean Peninsula more prone to turbulence.

This extreme cold is primarily driven by the jet stream, which usually circulates around the Arctic but dips southward over the peninsula. This shift brings frigid Arctic air, driving temperatures even lower.

Turbulence tends to form near the jet stream, where strong wind currents with significant speed differences converge, creating unstable airflows. These areas are particularly susceptible to turbulence due to the sharp contrast with surrounding air.

However, detecting jet stream-related turbulence is challenging for onboard weather radar, making it difficult for pilots to avoid. This phenomenon, known as clear air turbulence, often occurs in cloudless conditions, making it all the more unpredictable.

Aircraft weather radar cannot detect clear air turbulence. These systems work by emitting radio waves and analyzing the signals reflected by clouds or precipitation, making turbulence visible. However, clear air turbulence has no such reflective objects, rendering it essentially invisible.

This unpredictability means pilots often struggle to anticipate such turbulence, sometimes leading to accidents. For instance, in February 2013, a Korean Air flight from Incheon to Tianjin encountered undetectable turbulence, injuring two flight attendants who were standing and performing their duties.

To mitigate these risks, pilots rely heavily on reporting. When an aircraft encounters turbulence, the crew reports the location, altitude and intensity to air traffic control, allowing controllers to warn subsequent flights and help them avoid the affected area.

There is also a rare visual indicator of clear air turbulence. Jagged, serrated edges in thin cirrus clouds can suggest turbulence nearby. While cirrus clouds themselves do not cause turbulence, their formation near turbulent air can serve as a subtle clue to these invisible disturbances.