Autumn offers some of the most beautiful flying days of the year, with golden landscapes and often crystal-clear air. However, this time of year also brings with it certain meteorological conditions that require pilots to be extra vigilant. As the days grow shorter and the nights cooler, the weather changes noticeably.
The invisible boundary: What is an inversion?
Normally, the temperature decreases with increasing altitude. In autumn, however, this principle is often reversed. The long, colder nights cause the ground to cool significantly. The air directly above the ground becomes cold, and because cold air is heavier than warm air, it settles close to the ground. A warmer layer of air then forms above it.
This so-called temperature inversion acts like a lid. The temperature rises with increasing altitude, which completely blocks vertical air exchange.
The result: sudden ground fog
Moisture accumulates beneath this warm inversion layer. The result for aviation: sudden ground fog and severely restricted visibility. What may still look like ideal flying weather at the departure airfield can, when flying at low altitude or along river courses, turn out to be a flying challenge within a very short space of time.
What pilots need to be aware of now
Before you taxi your Junkers out of the hangar, thorough pre-flight checks are essential in the autumn:
- Monitor visibility: Always keep an eye on the horizon and your return route so that you can turn back in good time if in doubt.
- Check the temperature-dew point spread: If the temperature and dew point (spread) are close together, the risk of sudden fog formation is extremely high.
- Plan alternative routes: Valleys and damp lowlands are the first places where fog tends to form. Plan alternative routes via higher ground.
However, anyone who understands and respects the meteorological rules of autumn will be rewarded with truly unrivalled flights.
For above the autumnal blanket of mist, there is usually bright sunshine and a view into the distance that is unique to this time of year.
