Early morning sea haar in Torry housing estate.

Image: © Colin Kinnear Taken: 3 Feb 2011

On the east coast of Scotland a sea fog, known locally as Haar, often plagues the local residents and ruins what would otherwise be a fine day. It most commonly occurs between April and September, on or near the east coast or in the Northern Isles. It does not usually penetrate far inland, but can filter through valleys like the Great Glen and the Central Lowlands as far as Glasgow. Haar forms when a parcel of warm air passes over the cold North Sea. The warm air at the bottom of the parcel is cooled by the cold air below, until it can no longer 'hold' the moisture that was previously contained within. Therefore, it releases some of the moisture in the form of liquid water through condensation. Add an onshore component like a wind of 5-20mph, and the cooling in the bottom of the warm parcel of air is spread upwards and generates a fog like Haar.

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