What causes Edinburgh’s haar?

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Readers can’t have missed the haar that has been around Edinburgh for the last few days, but what exactly is haar and what causes it?

Indeed, the Capital is known for fog and haar, why is Edinburgh, and the east coast in general, affected so much more than other parts of the country?

Aidan McGivern, a Senior Presenter and Meteorologist for the Met Office explained: “Persistent easterly winds this week have brought large areas of low cloud and mist from the North Sea to much of Eastern Scotland, known as Haar.

“Haar is actually more common at this time of year than any other.

“The North Sea remains chilly following winter but the air above it during this week has been drawn up all the way from the Mediterranean.

“When mild and moist air sits over chilly waters, you often get low cloud, mist, fog and drizzle.

“The easterly winds of this week have then brought those dank conditions to the shores of Eastern Scotland.”

And for those of you wondering the difference between “haar” and the more commonly heard “fog”, Haar refers specifically to the coastal fog which typically forms in Spring and Summer over eastern Scotland and England.

It occurs when warm air moves over the cooler North Sea, causing moisture in the air to condense and form haar.

The haar is then blown inland by the wind.

Variants of the term in Scots and northern English include har, hare, harl, harr and hoar.

Fog is a more general term referring to the weather phenomenon caused by tiny water droplets which become suspended in the air. It can form over bodies of land such as valleys and slopes, as well as over the sea.

The thickest fogs tend to occur in industrial areas where there are many pollution particles on which water droplets can grow.

There are several different types of fog, which are named according to the physical process which produces saturation or near-saturation of the air. The main types of fog include radiation, valley, advection and upslope fog.