"Bubble Bow"

This picture actually shows just a few air bubbles frozen in a sheet of ice. But when watching it from a certain angle against the antisolar point, I discovered these strange colours. These can be expressed as a kind of “inverted rainbow”, as the circumstances under which it formed are exactly reversed to those of a normal rainbow. In a rainbow, the spherical object consists of water, but in this “bubble bow” the spherical object consists of air.

But there is a crucial difference: The ordinary main rainbow is based upon a double refraction of light and one inner reflection. But in case of this “bubble bow” the light is refracted four times: When it enters the ice, it gets refracted for the first time. The second time is when it enters the bubble. Then it is reflected once (or several times?) inside the bubble before it gets refracted a third time when leaving the bubble and entering the ice again. Finally, it gets refracted a fourth time when it leaves the ice. The “bubble bow” formed by this procedure has the same sequence of colours as a normal rainbow. But I do not know if it can ever be seen as a whole.

Photograph taken in Barsinghausen-Egestorf (Germany) on March 5, 2010, with a Canon EOS 1000d camera. More pictures are here.

Author: Reinhard Nitze, Barsinghausen, Germany

„Glorydescent Clouds“

In the morning of March 1st, 2010, I made my second observation of „glorydescent clouds“. These are fragments of a glory which change very much in diameter due to the different size of the droplets towards the rim of a short-lasting foehn cloud.
This makes the sequence of the colours look asymmetrically.
The stratocumulus lenticularis cloud did not even last for 5 minutes and caused a bright and very changeable iridescence or “glorydescence” during this short period of time. When the colours reached their maximum, up to 4 systems of rings were visible, with the 4th one appearing in the cloud behind the glory.
The pictures were taken at 8.05 CET / 8.06 CET / 8.07 CET.

Hair Ice

Hair ice (in German Haareis) is formed at dead wood by conditions of high humidity and temperatures near freezing point. Water in the pores expands below 4°C and freezes on the surface. In this way fine ice needles were created. (1-2-3)

I found it in the Black Forest (Schwarzwald) in southern Germany.

Author: Helga Schöps, Germany

Halo Meeting of the “Arbeitskreis Meteore e.V. / FG Atmosphärische Erscheinungen der VdS e.V.“ at the Sudelfeld (Upper Bavaria), January 08 – 10, 2010

Winter halos in nearby ice crystals are quite a rare sighting in most parts of Germany. However, there are few special places where the chances for such displays are much higher, such as the Alps mountains. To benefit from this, 14 halo enthusiasts met at the Sudelfeld Youth hostel near Bayrischzell in the vicinity of the Wendelstein (1838 m) during the second weekend of January. Already on Thursday (January 07) a very impressive halo phenomenon at the sun could be observed by Reinhard Nitze. Unfortunately, throughout the meeting a complete cover of low-level clouds blocked the sun so that halo observations were restricted to artificial light sources during night time. The highest halo activity was noticed at late Friday evening, involving light pillars (or superlamps), upper and lower 22° tangent arcs (“champagne glasses”), parhelic circles (visible for only few seconds), and superparhelia (not photographed due to fleeting appearance). The phenomena showed remarkable dynamics, lasting for about 10 minutes and being followed by intervals of 30-60 minutes without halos. The influence of snow blowers was discussed as well, since there were some of them running the whole night, approximately 500 m apart from the observation place.

Photo: Claudia Hinz

During the second evening only weak light pillars were seen for short times, eventually being replaced by fog bows due to rising temperatures and the transition from ice crystal to water droplet fog. Great fun were the shadow plays using a floodlight in the back of the people what finally led to photos of the “Sudelfeld monster”.Apart from the actual observations, the participants joined a workshop program containing slideshows from Michael Großmann, Claudia Hinz, Reinhard Nitze, and Andreas Zeiske as well as talks dedicated to special topics such as halo image stacking by Georg Dittié, high dynamic range image processing by Claudia Hinz, high precision measurements of the moon’s opposition effect by Elmar Schmidt, microphotography of snow and ice crystals by Reinhard Nitze, and artificial dew bows as well as stereo photography by Alexander Haußmann. The following experimental demonstration of glass bead bows in divergent light was received with great interest and triggered a high amount of photographic activity. Furthermore, an excursion to the nearby Tatzlwurm waterfall (named after some kind of dragon) was organized at Saturday afternoon and revealed a great winter landscape containing a large number of worthwhile photo subjects.

Photo: Udo Hennig

More pictures are here.

Author: Alexander Haußmann, Hörlitz, Germany

Colours inside a cracked piece of ice

After some very cold days in Heréd (Northern Hungary) Karoly Viczian went out to the garden to break the ice in a rainwater collecting barrel. On a small piece of ice he cut out from the barrel he could see some very vivid colours - it reminds me to the diffraction colours of an opal gemstone. So maybe the coloures were produced by some microscopic bubbles inside the ice just the same way as they form in the gemstone that has small spherical structure . But Károly said he had noticed the colours after breaking up the ice, so it seems that the small cracks inside might have produced them with the help of birefringence.
As Károly told me the ice was the outcome of multiple freezing and melting periods, so it might also have separate layers inside. He has more pictures of the same piece of ice. The water was simple rainwater, only some fallen walnut leaves were at the bottom of the barrel, nothing was put in it willingly.
What is the correct explanation of this phenomena?

Iridescent Fireworks Smoke

Like everywhere around the world, New Years Day was also welcomed with fireworks around Mt. Wendelstein. It is always a special highlight to watch the fireworks from the top of the mountain at 1838 meters above sea level. In the Leitzach Valley, about 1000 meters lower, there was a fireworks display.
Even when watching it with the naked eye, the smoke and fog of the fireworks seemed to show iridescent colours. The photographs (photo) show the iridescence more obviously. It was probably caused by the condensation nuclei from the fireworks smoke, on which small droplets condensated. As short time before an area of precipitation had passed, air humidity was still very high.
Additionally, the fireworks caused a thin layer of fog over almost the whole alpine foothills area (photo), and the big city of Munich with more than a million inhabitants, was covered by a thick layer of clouds (photo).

Similar things were reported by other observers. In Bochum, Peter Krämer observed that light graupel turned into snow during the fireworks, leaving about a centimetre of snow. On the weather radar it could be seen that a precipitation area formed right over the Ruhr area just after midnight.
Two years ago, thin fog with visibilities around 300 meters thickended after the New Years Fireworks, forming a dense layer of fog with visibilities which were less than 10 meters in some places.

Northwestern Germany Diamond Dust Sun Pillar

Diamond dust halos are normally observed in northern regions of Europe, or in the mountains where temperatures in winter often drop sufficiently for the formation of ice crystals near the ground.

On December 19, 2009, there were several reports of diamond dust from the lower parts of northwestern and western Germany, which formed widespread sun pillars.
With temperatures of about -14°C, I also witnessed an upper and lower sun pillar in Bochum, Germany.
The lower sun pillar was visible in front of trees and even the snow-covered ground, as the picture taken at about 9 hours CET shows with the sun hidden behind a sign-board.
I could also see the ice crystals glittering in the air, making the pillar appear three-dimensional, as if a ray of light extended from the sun right up to my eyes.
The upper part of the sun pillar was visible for about half an hour, while the lower part and the glittering of the ice crystals stayed for about 3 hours until noon.

Author: Peter Krämer, Bochum

Crepuscular rays in desert dust

After the twilights had been getting normal through the past three weeks, where hardly any volcanic aerosoles from Sarychev volcano had been measured, I was very astonished when I saw an intense purple light with crepuscular rays about half an hour before sunrise (sun elevation at -6°) in the morning of November 17. The crepuscular rays crossed the whole sky near the horizon, converging at the antisolar point (1 - 2 - 3).

Of course I immediately asked my colleagues from the Hohenpeissenberg observatory about the phenomenon. And I got a very surprising answer:
At that moment there were two different layers of dust from the Sahara desert above us, a lower one at an altitude of about 8.5 kms with dust from the western parts of the Sahara, and a higher one at about 11 kms, which contained dust from the eastern part of the Sahara. There were two different currents of air at higher levels which overlapped each other above the Alps.
It is new for me to learn that such twilights are also possible in desert dust, just as this dust up to now only caused a kind of certain dimness in the air. But at that moment there was no desert dust directly above us; I only looked into the layers of dust.

However, there was an extra bonus on the next morning. Unfortunately could only watch it from the valley:

Twinned rainbow

Mark Worme observed this rainbow today at around 3.15 pm Atlantic Standard Time in central Barbados facing east. At first he only noticed the double rainbow, but then he realized the lower one was split.

During a heavy rainshower, a twinning of the upper part of a rainbow can sometimes be observed, which often lasts from a few seconds up to several minutes. As for a long time there were only few observations of this phenomenon available, only speculations could be made about its origin. Only in the past few years, this twinning could be registered more often by continuous observations, and due to some detailed descriptions, new theories could be advanced. As in all observations both bows are of equal brightness, light refraction on ice particles can be ruled out. Most probably is that raindrops of a non-spherical shape produce one of these bows or even both of them. Due to surface-tension, small rain droplets hardly change their shape when falling, but large drops can be flattened by the air resistance. The more flattened they become, the smaller is their refractive index. So the sunlight has to fall upon water drops of different size at the same time to make the twinning appear. As this twinning was up to now observed under big shower or thunder clouds which formed in hot air, it can be supposed that the small, not flattened raindrops evaporate at a short distance below the cloud basis. This would explain why the twinning can only be seen for a short time and exclusively in the upper part of the rainbow. It should be important to determine the radius of the rainbow when the twinning is observed, and to record the weather situation at the time the twinning appears as exactly as possible.

Shadows and lights of a flight

Many people find flights boring - but not all! If you are lucky to be seated by a window you can always find something interesting in the air beside or below the airplane. David Lukacs from Hungary took this picture on 2nd November 2009 on a flight from Rome to Budapest, about 15 minutes after the departure. A thin layer of haze was between the plane and the sea so the sun shining on the right side above the plane could cast radial shadows on the left below. The beams of shadow and light join at the antisolar point.



A bit later when the plane travelled above a cloud layer David also noticed a nice glory below them:



Even the shadow of the airplane appeared in the middle: