Halo Phenomena in Contrails

[Alec Jones]

Hi Everyone,

I have a couple of questions regarding the formation of halo phenomena in aircraft contrails.

Firstly, how common do you think they are?

Secondly, what types of halo phenomena have you observed forming in contrails?

I see parhelia quite often and occasionally the odd CZA. However, I don't recall seeing any other type. I have also seen images of a 120 degree parhelion and a subsun in contrails somewhere on the net. This would suggest that plate rather than column crystals are predominantly associated with aircraft contrails. Considering their ubiquity, I have yet to see a UTA forming in contrails.

Any thoughts?

Regards,

Alec

[Elmar Schmidt]

Hi Alec,

you have a good point here. I think, both cirrus cloud cover and halo activity are very much enhanced by contrails.

viewtopic.php?f=2&t=10531

According to my studies, a good part, if not the majority of CHA sightings originate in old contrails, so plate crystals should be prominent, but probably not dominant. Christoph Gerber and myself, we photographed a CHA and later =CORRECTED= LTA in the same contrail, only ten minutes apart, cf.

viewtopic.php?f=2&t=10543
viewtopic.php?f=2&t=10544

Regards, Elmar

[Reinhard Nitze]

Hallo Alec/Elmar!

Sorry, i can't post this in english.

Das ist wirklich eine gute Frage. Es gibt immerwieder Fälle, wo Kondensstreifen die Grundlage von Haloerscheinungen sind, manchmal schon nach erstaunlich kurzer Zeit. Trotzdem bin ich der Meinung, das sich Kondensstreifen eher kontraproduktiv bei der Halobildung verhalten. Ich konnte schon häufig beobachten, dass beispielsweise nach einem Kaltfrontdurchgang der Himmel zunächst eine tiefblaue Farbe hatte, insbesondere am frühen morgen. Schon kurze Zeit später tauchen die ersten Kondensstreifen auf, und nach und nach überzieht sich dann der gesamte Himmel mit einer Mischung aus streifigen Cirrostratus und verschmiertem Cirrocumulus. Optische "Knalleffekte" sind darin aber (meiner Meinung) die absolute Ausnahme. Ich denke, dass es nur dann zu guten Erscheinungen kommt, wenn die Rahmenbedingungen ohnehin schon so sind, das auch in anderem (sprich: natürlichem) Cirrus Erscheinungen möglich sind. Da kann natürlich ein Kondensstreifen genau in dem optisch wirksamen Bereich des Beobachterstandorts die entsprechende Erscheinung hervorrufen. In der Regel aber bewirkt ein Mehr an Feuchtigkeit und Kondensationskernen eine zu rasante, unregelmäßige und damit qualitativ schlechte Kristallbildung. Die optische Wirksamkeit geht damit "flöten" mit entsprechender Auswirkung auf die Haloentwicklung.

Wenn uns die Natur in der Höhe ein Halosüppchen kocht, dann kann es sein, das die Kondensstreifen das Salz in der Suppe sind und die Halos zur Entfaltung bringt. Doch wie es eben immer so ist, ein Zuviel davon, und das Süppchen ist verdorben. Wie sagt man doch so schön? Viele Köche verderben die Köchin . Und das geschieht leider viel zu oft und allzuschnell...

Viele Grüße, Reinhard

[Elmar Schmidt]

Hallo Reinhard,

vielleicht habe ich mich nicht präzise genug ausgedrückt (auf Englisch). Tatsächlich korreliert z.B. die ZHB-Häufigkeit in meiner weltweiten Studie eher invers mit der Cirrendichte (aus Arbeiten von K. Sassen), wie weiterhin auch klar ist, daß die meisten Cirren keine Halos machen. Insoweit hast Du völlig recht.

Andererseits kommt es m.E. durch das Hinzutreten "künstlicher" Cirren in Form von Kondensstreifen unterm Strich zu einer Vergrößerung der Halohäufigkeit, auch wenn ebenfalls nur eine Minderzahl derselben gute Kristalle ausbildet. Schau bitte mal selbst nach ZHB-Bildern, die zeigen zu hohem Anteil alte Flugzeugcirren. Damit zusammenhängen mag auch, daß ZHBs vor 100 Jahren recht selten berichtet und dann meist als "horizontale Regenbögen" fehlgedeutet wurden.

Natürlich sind Häufigkeitsstudien schwierig, weil es mit dem Zeitalter des Flugtousrismus im Durchschnitt wohl auch mehr Halobeobachter gibt. Interessant wäre trotzdem, ob die langen Reihen der AKM-Statistik hier belastbar eine Zunahme zeigen. Mit dem Sonnenfleckenzyklus deutet sich da ja auch was an.

Gruß, Elmar


PS: hier im Moment ein schöner OBB/UTA.

[Alexander Haußmann]

Hi everybody,

I've seen some halos in older contails last year in the Netherlands:

viewtopic.php?f=2&t=9886&p=46466#p46466

The most common halo seems to be the 22° parhelion. I also think that plates are dominant, or do become so after some time. Maybe there are similarities to the Davos snow guns that also emit condensation seeds generating halo crystal clouds some 100 m off.

Kind regards,
Alex

[Alec Jones]

Thanks Elmar, Reinhard and Alexander for your replies so far. Very interesting.

I first became interested in this question after reading a passing comment on Marko Riikonen's blog submoon,

http://submoon.wordpress.com/2011/05/11 ... on-11-may/Marko says,

"Halo contrails are quite rare in Finland. Wonder what is the rarest halo seen in contrail? I recall there is some foreign report about an anthelion in contrail. Maybe from the Netherlands...."

This got me to thinking how frequent or infrequent halo phenomena in contrails actually are. I live near a major international airport (Manchester) and my skies are invariably full of contrails given the right conditions. Consequently, I tend to see 22° parhelia on a very regular basis. Looking back through my image archive, I also note that besides a few CZA's I also have a couple of 120° parhelia in contrails.

Elmar, it is interesting that you and Christoph photographed a UTA in contrail; that is the first instance I have come across of a column crystal generated halo. Also intriguing the fact that you say that historically the reports of CHA's were not as numerous as they are now and that most modern observations probably originate in old contrails. Whilst that does not mean to say that CHA's are a man-made rather than a naturally occurring phenomenon, because reports of them obviously pre-date the coming of contrails, their frequency might have increased due to the presence of contrails. Indeed, might there maybe a similarity to the relationship which exists between the Molianen Arc and snow guns?

It would be interesting to find out whether plate and column crystals are present in equal measure in contrails and if so why plate generated halos seem to be the more numerous. Likewise, given the fact that there might be a similar number of contrails in two different geographical locations, why halo formation in contrails might be more prevalent in one location than the other. It is very difficult for me to believe that I might see more halos in contrails than the "halo gods" in Finland!!!

Best,

Alec

[Elmar Schmidt]

Alec,

please take note that my 2nd observation =now corrected= from July 1st, 2013, was not a UTA, but a LTA or part of a circumscribed 22 deg, which would also point to column-like crystals. If you look at the splitting of its left end, there remains a puzzle, still, what this really was, as the 22-deg, typically, is less colourful than its tangent arcs or circumscription.

Elmar

[Kevin Boyle]

Alec,

(Really shouldn't write when I'm half asleep but anyway)

Difficult to say.

The upper tangent arc and parry arc that we witnessed last year (and your photos of the parry arc are on this forum somewhere) was due to extensive contrail cirrus.

On 10 August an old contrail became a feather plume fallstreak and this was responsible for a bright to very bright upper tangent arc, halo, parhelia, parhelic circle and a 120 degree parhelion. More often than not, parhelic circle fragments and 120 parhelia are commonly seen in ex-contrails...and I have seen a fair few upper tangent arcs in old contrails and, of course, 22 degree halos or their fragments are commonly seen as well. Perhaps it is because a lot of them are faint and you don't notice them?

Contrails were responsible for last night's (2 September) bright and persistent upper sun pillar (6 degrees), the final part of this, at last, disappearing with the sun around -6 below the horizon.

2013 has not been a great year for halos so that might make things seem rarer.

Best,

Kevin

[Christoph Gerber]

Hi,

I have seen yesterday the fragment of an Infralateral Arc in a contrail - but unfortunately I could not take a photograph of it: see ILB an Kondensstreifen

Christoph

[Alec Jones]

Hi Kevin & Christoph,

Sorry it's taken me so long to answer.

I had actually forgotten about the Parry & UTA you mention. Looking back over the images it was indeed formed in old contrails. As you know, Kevin, I also got another Parry, UTA and Upper Lowitz, the other day which was in all probability formed in contrail based cirrus,

http://theboltonhalotriangle.blogspot.c ... -hand.html

Thanks for that, Christoph, another halo type to add to the list! Perhaps halo formation in contrails isn't quite as unusual as I first thought.

Best,

Alec