The surface temperature inversion in the subarctic setting of Fairbanks, Alaska has been investigated. In winter the inversion is strong and semipermanent; it separates the boundary layer from the air aloft and has great importance for pollution levels in town. We are especially interested in the changes which have occurred since radiosonde measurements began in 1957, during which the winter mean surface temperatures have increased by 3.3°C, more than for any other season.

The climatology of the surface-based temperature inversion is examined by analyzing the twice-daily radiosondes for December, January and February from 1958 to 2004. While there has been no significant change in the frequency of occurrence of surface-based inversions, the depth as well as the intensity of the inversion has decreased.

The change in characteristics of the inversions is discussed and the role of cloudiness and winds is demonstrated. Increasing cloud amount weakens the surface inversion due to increased back radiation from the atmosphere, while strong winds aloft can erode the surface inversion due to forced mixing.