Smog — niska emisja
Poland has among the worst particulate air in the European Union, and the reason is specific enough to forecast. It is not traffic and it is not heavy industry. It is niska emisja — “low emission” — the smoke from a few million individually fired household stoves burning coal and wood at roof height, in a country where the heating season is five months long and the winter anticyclone puts a lid on it.
The source is domestic
Roughly half of Poland's PM₂.₅ comes from residential heating. Emission at four metres does not disperse the way a power-station plume at two hundred does — it stays in the layer people breathe.
The lid is meteorological
On a clear winter night the surface radiates away its heat and the air above stays warm. That inversion is a lid, and everything emitted under it stays under it.
Which makes it forecastable
A weather model that resolves the lowest few hundred metres knows when the lid will form. COSMO publishes temperature on fifty model levels, so this site can draw it.
The inversion, straight off the model
IMGW's COSMO run publishes air temperature on fifty hybrid levels, and the constant file gives the height of each one above the ground. Over this domain the centre of layer 46 sits 180 metres up. So the inversion strength is a subtraction:
inversion = T(180 m) − T(2 m) [K]
Positive means warmer air sitting on colder — a lid. On a clear anticyclonic January night over the Polish lowlands it is routinely +3 to +8 K, and the Kraków and Nowy Sącz basins hold it longest because their cold air has nowhere to drain to. Negative means the surface is warmer than the air above it, which is an ordinary sunny afternoon, and the boundary layer ventilates freely.
This field is published on its own — on the map explorer — precisely so the index below can be checked rather than believed.
The smog index, and what it is not
Three model quantities carry the whole story, and they multiply because all three are necessary:
w_inv = clip((ΔT + 1) / 4, 0, 1)
w_wind = clip((4.5 − U₁₀) / 3.5, 0, 1)
w_heat = clip((12 − T₂) / 12, 0, 1)
smog = 100 · w_inv · w_wind · w_heat
- ΔT is the inversion above. Zero weight at −1 K, a well-mixed layer; full weight at +3 K, a lid firmly on.
- U₁₀ is the 10 m wind in m/s. Full weight below 1 m/s; nothing above 4.5, which is about where PM₁₀ episodes in the Kraków basin stop.
- T₂ is the 2 m temperature in °C, standing in for heating demand. Twelve degrees is not arbitrary — it is the threshold Polish practice uses to define the start and end of the heating season, so it is the temperature at which the source switches on.
It is not a concentration. There is no emission inventory in it, no chemistry, and no knowledge of where anybody lives or what they burn. It says where the weather is loading the dice. Kraków and Nowy Sącz sit in basins and will be worse than it says; the Baltic coast will be better; and in July it is zero everywhere, which is correct.
What is actually being measured, right now
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These are the Polish Chief Inspectorate of Environmental Protection's own stations and its own six-level index — bardzo dobry through bardzo zły. The columns are the index for each pollutant separately, on the same 0–5 scale, so a station that is “moderate” because of PM₁₀ and a station that is “moderate” because of ozone are distinguishable.
Read them against the model. If the smog index is high over Małopolska and these stations are green, the index is wrong about that day and you should trust the measurement; if it is high and the stations are red, it told you a day in advance. That comparison is the reason both are on one page.
Summer note: the index is dominated by ozone in summer and by particulates in winter, so a “moderate” August afternoon and a “moderate” January morning are different chemistry entirely.
Worst stations now
| Index | Place | Voivodeship | PM₁₀ | PM₂.₅ | NO₂ | Measured |
|---|---|---|---|---|---|---|
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Pollutant columns are GIOŚ index values (0 = very good, 5 = very bad), not concentrations. powietrze.gios.gov.pl has the concentrations and the official map.