Diamond dust from Riihivuori snow guns

Towards the last weekend tension was rising among Finnish halo observers. It was going to be clear skies with sinking temperatures and full moon. Most of the ski centers had their snow guns running, so anticipation for diamond dust was high.

On Saturday, 4 November, Arto Oksanen drove to check the sitation at Riihivuori ski center. There was indeed a column crystal dominated display with upper sunvex Parry, as shown in the photo on the left.

Next night Arto did not have to go anywhere, since wind carried the ice clouds straight to his doorsteps, to Muurame town. It was Parry-time again, and now in addition to normal upper suncave there was also the much less commonly seen lower sunvex Parry (photo on the right). Untill the last winter the latter has been considered as an extreme rarity, but now reports have increased, thanks mainly to ski centers' snow guns and active observers around them. The display contained also other halos of interest, like Wegener anthelic arc and anthelion. See also Juha Oksa photos from Muurame the same night.

 

by Marko Riikonen

 

Originally in Halo reports 

Lower Parry arc in Antarctica region

Joe MacGregor observed very rare Lower Parry sunvex arc in Antarctica. Joe say: "The photo was taken about January 19, 2006 somewhere within ~100 km of 79S, 117W. It was taken with a point-and-shoot Canon S230." More photos halos are here. Simulation is made with Halosim by Les Cowley and Michael Schroeder. This Sun display with Lower Parry sunvex arc is probably second case of the World.

Lunar Tricker arc and lower sunvex Parry arc in Finland

Tricker arc is not very common in lunar displays. That is not a big news, since it is often faint also in daytime displays. In Rovaniemi, a town at the Artic circle, Olli Sälevä observed this diamond dust halo display in 11 Feb 2006.

Other rare halo in the display is a lower sunvex Parry arc which was found later in one slide. Lower sunvex Parry arc is even rarer than Tricker arc. Unfortunately it is only faintly visible below lower tangent arc near horizon. In the lower picture picture red arrows points the red inner edge of lower sunvex Parry arc. Picture is enhanced to show the faint arc better.

Other halos in this lunar display were a Parry arc and a faint infralateral arc and a parhelic circle. Also street lights has halos around them like Y-shaped upper tangent arcs and parhelic circle look-alike parhelia. Olli photographed the display with film camera. He was not sure, but he thought that there was something going on opposite to the moon. So he took a photographs toward anthelion region as well. It was a nice surprise to him to find a Tricker arc in photos. Since moon elevation was close to 30°, Tricker arc is visible here only downward from the parhelic circle. Photo shown here is enhanced to look more like the original slide.

More photos taken by Olli Sälevä can be found here (rescanned versions will be upload later).

Lower sunvex Parry in Finland

Lower sunvex Parry is a halo of which for long time only one certain report was known: the photograph by Takeshi Ohtake in 1979 in Alaska, shown in Walt Tape's book "Atmospheric Halos". 

Now the sightings of lower sunvex Parry seem to be increasing. Last winter it was photographed twice in Finland and this winter we have two reports as well. Picture above is the latest sighting of lower sunvex Parry (arrow), by Marko Mikkilä at Sievi on the night of 15/16 January 2006. The display was caused by snow machines from nearby ski resort. Moon elevation is 40°. 

Winter's first sunvex Parry was seen on 8. January 2006 at Himos ski resort. Photos of the display by Mika Aho are seen here. Simulations with different crystals are here.

Mikkilä display had also other rare halos. He reports lower Tape arcs, Wegener arcs, helic arc and subhelic arc. Also interesting halos from car headlights were present.