Wednesday, 8 February 2017

Diamond Dust and Air Pollution in Hungary

By: Zsuzsanna Sándor-Tóth (Hatvan, Hungary - 29 January 2017)
Diamond dust halos are scarcely observed phenomena in Hungary, mostly because of our climate. When it is cold enough, dry airmasses of Siberian origin fill the Carpathian Basin. But when the air is moist enough, it is not really cold. Special locations, however, share some attributes needed for diamond dust formation: at ski resorts with snowguns, for example, condensation seeds are present. Interestingly, this year’s Hungarian diamond dust observations, show a different type of seeding.

Industrial districts are well known for ‟industrial snow” production around the world because of their seeding - and this is the same with diamond dust for some locations. Also some places (mostly less advanced regions, small rural towns and villages) have houses with an old heating system based on wood and coal, and we all know how much air polluting soot particles these create. We also noticed diamond dust formation near highways, which are also a ‟good” source of air pollution

In winter Hungary usually has some weeks of high pressure weather which in our case means cold, foggy days with only a small amount of sunshine once in a while. These weeks help accumulating a dense, highly polluted air, especially in valleys (while the highest hills still might be clear). If the temperatures are low enough, and there is enough moisture present (imagine a river valley for example where fog formation is always possible), and these circumstances coincide with local air pollution, diamond dust might form, no matter if it is industrial or due to high traffic or heating.

Still some kind of light source is needed for any halo... We see diamond dust falling without any optical side-effects on grey, foggy days, and sometimes when it happens at night, we might see light pillars. During rare hours when the Sun decides to look at our pale faces there might be some sundogs, 22° halos, sun pillars, tangent arcs, CZA too. But mostly we see only a small amount of diamond dust glinting around us in the air, maybe a weak subsun with it. 90% of these displays are very faint, last only for a short time and are limited to a small area.

My personal experiences from this winter have been that almost every foggy night there was some diamond dust falling. It, however, made not even a single light pillar, as it was observed only within a 20-30 meter area. Typically, I could only see diamond dust forming around one certain house which was wooden heated. Ákos Ujj saw similar cases around a central heating supply building near his home ‒ although farther away the conditions (fog and low temperature) were the same.
By Tibor Tátrai (Tápiószőlős, Hungary - 10 January 2017)
Tibor Tátrai is our ‟diamond dust king” as he has the most abundant observations in our country. For some years he has been collecting these observations from his village and the nearby town where he attends school. Both places have air pollution, the village because of the heating, the town because of a small industrial district near the road which he travels each day and where he usually sees diamond dust halos. He also has temperature records for these observations and it was not uncommon to see a diamond dust halo with only -3,5 / -6°C instead of the more proper below -10°C temperatures (still this winter he was at the lower edge with several light pillars seen with -15/-17°C). He lives at Tápiószőlős which lies at a lowland with lots of small creeks and irrigation channels nearby ‒ these keep the moisture high there. Similar circumstances are present at his school town (only 10kms from the village) and there is also a highway right beside the industrial district, so maybe industrial and traffic air pollution is added up there.

By: Zsuzsanna Sándor-Tóth (Hatvan, Hungary - 29 January 2017)
Another location where a nice display appeared and lasted for about 1,5-2 hours is Hatvan, a town by a main highway and also with a river. That town also has some industry but not any special air polluting type (and a new gas-heated power station which is not producing condensation seeds).

By: Mónika Landy-Gyebnár


  1. Interesting post, Mónika. Just a thought, but I wonder whether the particulate matter of different pollutants are prone to forming crystals of a particular type?

    1. According to air pollution measurements both PM10 and PM2.5 were abundant in the country these weeks, this might mean both soot and dust particles, but I have no idea which of them dominated the better cases with some type of halo. :-(

  2. The crystal type should be mostly affected by temperature. And humidity too. The properties of the particle affects the temperature at which it becomes an active ice nuclei.

  3. Interesting. I live in one of the most polluted places in Czechia with PM10 and PM2.5 concentrations sometimes exceeding 10x the "healthy limit," and haloes in the city are almost non-existant.