A cold wave is a weather phenomenon that is distinguished by a cooling of the air. A cold wave is a rapid fall in temperature within a 24 hour period. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year. Usually cold waves are measured by the difference from the normal temperature. Cold waves generally are capable of occurring at any geological location and are formed by large cool air masses that accumulate over certain regions, caused by movements of air streams. Cold waves affect much larger areas than blizzards, ice storms, and other winter hazards. The “wave” in cold wave is apparent in the upper-air flow (the jet stream), which is usually amplified into a strong ridge-trough pattern during a major cold outbreak.
The cold wave can negatively impact the safety of aviation operations. To mention some of the most significant issues associated with cold wave:
- Ice and frost accretion on the critical external surfaces of an aircraft.
- Extremely cold temperatures can stress the metal aircraft surfaces.
- Vehicle batteries are strained and diesel fuel gels in extreme cold weather which could have a negative impact on ground operations, etc.
Formation of Cold Waves
In the Northern Hemisphere, cold waves occur when very cold, dense air near the surface moves out of its source region in northern Canada or northern Asia.
The core of a cold wave at the surface is a strong high-pressure center that forms during winter in high latitudes. Cold polar or Arctic air masses are relatively shallow, extending one to several km above the surface. The surface high-pressure center of the cold air is accompanied with a upper-level convergence. The most extreme area of all is northern Asia (Siberia), where the formation of cold surface air is enhanced by the large distance to the nearest unfrozen ocean, isolating the area from warmth and moisture, and the presence of mountains to the east and south, serving as barriers to trap and further isolate the cold surface air once it has formed.
Cold Waves in Europe
The 2009 European Cold Wave gave most of Europe, especially central and southern areas, very cold temperatures. Some places such as Germany, France, Italy, Romania and Spain had record cold temperatures well below 0 °C (32 °F). Most of these places were also covered in snow and ice which caused many airport delays.
The 2012 European Cold Wave was a noteworthy temperature anomaly that started in January 2012 and brought snow and freezing temperatures to much of the European continent. Particularly low temperatures hit several Eastern and Northern European countries, reaching as low as −39.2 °C in Finland. The heaviest snow was recorded in the Balkan region. In February the snow reached the British Isles, causing interruptions at London Heathrow Airport where up to 10 cm (3.9 in) of snow impeded many scheduled flights.