Condition of low visibility associated with anticyclones accompanied, in the colder months of the year, by well-developed temperature inversions that can trap dust and other pollutants, and often have radiation fog in the lower layers. The stability of the high-pressure system can make the resultant reduced visibility very persistent and may establish smog conditions.
Geography
In winter, in north-west Europe, fog, or poor visibility caused by broad, persistent sheets of strato-cumulus cloud at the base of an inversion trapping polluted air below. The inversion results from the arrival of a cold anticyclone.