2007. március 25., vasárnap

A spring-starter in Finland

On 25th March a relatively small high-cloud area swept over Southern Finland and produced a fine halo for observers in Helsinki, Espoo, Turku and Riihimaki. In Riihimaki the upper Lowitz arc was continuously in the sky for over three hours. In addition to Lowitz, there were also pyramidal crystal halos (9 halo/column arc?, 24 lower plate arcs, 18 plate arcs), helic arc and Wegener anthelic arc.

The photograph above is taken by Jukka Ruoskanen, and more photographs can be found here. In Helsinki the display was photographed by Marko Riikonen, in Espoo by Panu Lahtinen and Timo Kuhmonen and in Turku by Ismo Luukkonen

2007. március 7., szerda

Wegener arc on webcam

On Mar/3/2007 I captured a halo display with a remote webcam in Oklahoma/USA. The camera image shows a bright parhelic circle, 120° parhelion and a rare Wegener arc forming a cross on the parhelic circle. A time lapse movie is available here: 

2007. március 6., kedd

Mid-elevation halo display with column crystals in control

Throughout my work day there were a number of halos that were coming and going. Around midday there was 22d halo, circumscribed halo, parhelic circle, and parhelia. Later on at break time I got 22 and circumscribed halos and there was a nice infralateral arc on the left and a possible lower suncave parry arc not sure on that need help to identify short piece of arc to the left of 22d halo. Before I left work I imaged an upper suncave parry arc. The final stage had nice upper tangent arc and a complete supralateral arc.

Odd radius halos in diamond dust in Finland

On 23 February an another diamond dust display with odd radius halos occured in Vaala, Finland. Temperature was dropping from -29°C to -24° during my observation.

A parhelic circle and circumzenithal arc were present with nice parhelia. A subsun and subparhelia were also seen as sparkling ice crystals in front of the ground.

Odd radius halos labelled in this enhanced photo are A) a pyramidal heliac arc, B1) upper 24° plate arc, B2) lower 24° plate arc and C) upper 23° plate arc.

The most brightest odd radius halo was 18° halo and in some photos there probably are also 9° upper plate arc and 20° halo. The ice crystal cloud was produced by a local heating plant about 2 km away. More photos can be found here.

2007. március 5., hétfő

Upper Lowitz arc in Germany

On February 21, Wolfgang Hamburg was on holiday in the Erzgebirge, but rather had snow there. Around noon, the cirrus clouds which already had caused an unusual halo activity in Bavaria (see one thread below), arrived at his position in Mulda. So between 1 and 1.30 pm, Wolfgang Hamburg also observed unusually bright sundogs followed by a beautiful display showing Parry arc and upper Lowitz arc. The enhancement of the unsharp mask shows the arc in the "Chinese eye" formed by the halos.

2007. március 1., csütörtök

Probable fragment of subheliac arc

On February 20 there were a lot of cirrus shreds in the foehn area of a strong northern low pressure area. Already in the morning there appeared unusually bright sundogs and a circumzenithal arc of the same brightness in these cirrus shreds. Later also a Parry arc appeared together with parts of the parhelic circle and very bright 120°-parhelia which had an accentuated reddish rim. At 11.50 CET, another arc seemed to form above the left 120°-sundog which stayed at its position for about 10 minutes while the cirrus clouds kept moving on. As the simulation for a sun elevation of 24° shows, the position of that arc fragment is identical to the subheliac arc.