Frequency of glories from different observation levels
The combination of spectre of Brocken with glory and fog bow is named after the German Brocken mountain, even though it cannot be observed there too often. My colleagues from the weather station estimated a frequency of 2 or 3 observations per year at the top of the mountain. The phenomena much more frequently observed at higher mountains.
Since there is no reliable statistics about the frequency of Glories to date, I tried to obtain some tendencies from my own observations on various mountain tops.
I observed at three different mountain tops where I worked for a longer amount of time:
- Mount Fichtelberg, Ore mountains, 1214m (similar height as Mt. Brocken)
- Mount Wendelstein, Alps, 1838m (standalone rock)
- Mount Zugspitze, Alps, 2963m (main mountain chain of the Alps)
Fichtelberg I observed most frequently in the early morning hours without interferences. On Mt. Wendelstein the Glories often long duration phenomena, sometimes very colorful with impressive interferences. On top of Mt. Zugspitze the Glory was visible at every solar altitude, in most cases long duration, with impressive interferences an colors.
I tried to capture the frequency of glory statistically. Since I could not look at the same time periods, the statistics is an approximation.
These observations lead to the following conclusions:
- The frequency of glories increases with altitude (at my observing sites the number of glories increased by a factor of three for every 1000m altitude)
- The higher the altitude of the observation point, the more impressive are the glories! With increasing altitude of the cloud, the size of the droplet in the clouds decreases and interferences become more frequent. Because the smaller and more uniform the droplet size, the more impressive becomes the glory (Simulation of Les Cowley). In the best case, the glory transforms into interferences of a cloud bow.
- The duration of the phenomenon increases with the altitude, too. If the local conditions allow observations well below the horizon, the glory is possible at every solar altitude.
Author: Claudia Hinz, Schwarzenberg, Germany