Għarb

Għarb is the network’s only Rural-Regional station, and that classification makes it the most analytically useful site of the five. A rural regional monitor is sited to measure the air of a region rather than of a settlement or a street, so what it records is substantially what the air mass over the islands is carrying.

At 114 metres above sea level it is also the highest station, and it is the only one on a different island from the network’s two Traffic-classified sites. Elevation and distance from the classified traffic sites both point the same way: comparatively little of what it measures is likely to have been emitted nearby. Where Malta’s traffic is actually heaviest is not something the station records say, and this page does not guess.

This is what makes it the key station for recognising a regional episode. When coarse particles rise at Għarb as much as at the urban sites, the cause is an air mass over the islands — Saharan dust, most often — and not the road outside any of them. No other station in the network can make that distinction, because no other station is far enough from local sources.

It is also the only station on Gozo at all, and it is one of the three that report all five pollutants. Ozone in particular is worth watching here: away from the traffic that destroys it locally, a rural site is where the regional photochemical signal should show up most clearly. Whether it actually carries the islands’ highest ozone on a given day is a question for the measured pattern below, not for this description.

The daily pattern here, measured

Worked out from this station's own measured hours — forecasts and gap-filled estimates are excluded, so this describes what the instruments actually recorded. The upstream feed carries roughly ten days of history, so this is the shape of a short recent sample rather than a seasonal average.

• PM2.5 is typically highest around 20:00 (10.8 µg/m³ on average) and lowest around 15:00 (6.3 µg/m³) — a moderate daily cycle, with the peak running 1.7× the trough. (264 measured hours over 11 days)

• PM10 is typically highest around 20:00 (16.7 µg/m³ on average) and lowest around 15:00 (9.4 µg/m³) — a moderate daily cycle, with the peak running 1.8× the trough. (264 measured hours over 11 days)

• NO₂ is typically highest around 09:00 (4.7 µg/m³ on average) and lowest around 17:00 (1.3 µg/m³) — a pronounced daily cycle, with the peak running 3.5× the trough. (264 measured hours over 11 days)

• O₃ stays broadly level through the day here, averaging 100.7 µg/m³ with no pronounced peak — the swing between its highest and lowest hours is under half again. A pollutant that does not follow a daily rhythm is usually one arriving with the air mass rather than being emitted nearby. (264 measured hours over 11 days)

• SO₂ stays very low here throughout the day, averaging 0.6 µg/m³ — far below the top of its Good band. At these levels the hour-to-hour differences are within the range of instrument noise, so no daily pattern is claimed from them. (264 measured hours over 11 days)

What this station answers best

The regional background — what the air arriving over the islands is carrying, independent of any local source. It is the reference against which every other station should be read.

What it cannot tell you

• It is one station for the whole of Gozo. Wherever you are on the island, the nearest monitor may be several kilometres away and in a quite different setting.
• A rural baseline understates what anyone in a town or beside a road is breathing. It is a reference point, not a description of exposure.
• Being the only Gozo site, there is nothing to compare it against on the same island — a local effect at Għarb cannot be separated from a Gozo-wide one.