Low-Level Temperature Inversions in Fairbanks, Central Alaska

Gerd Wendler Geophysical Institute, University of Alaska, Fairbanks, Alaska 99701

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Philip Nicpon Geophysical Institute, University of Alaska, Fairbanks, Alaska 99701

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Abstract

Low-level inversions up to 200 m were investigated on a statistical basis for Fairbanks, Alaska, using hourly data for the year March 1967 to February 1968. Surface inversions were found to be present for more than 50% of the time. In winter (November to February) there is an inversion for more than 95% of the time; maximum values of the inversion strength were 20°C in 200 m altitude difference. In summer (June to August) inversions occur relatively seldom. For the rest of the year, inversions are normally established at night, but are destroyed by day.

The strength of the inversion was analyzed and shown graphically as a function of different independent meteorological parameters for the four seasons and annually. Although there are some differences depending on the season, the strength of the inversions was observed to increase with a) negative net radiation, b) decreasing cloudiness, and c) decreasing windspeed. Furthermore, during the winter a northerly wind direction, probably of orographic origin, was associated with stronger inversions. Such graphical data for a typical subarctic community should be useful in local forecasting and pollution control planning.

Abstract

Low-level inversions up to 200 m were investigated on a statistical basis for Fairbanks, Alaska, using hourly data for the year March 1967 to February 1968. Surface inversions were found to be present for more than 50% of the time. In winter (November to February) there is an inversion for more than 95% of the time; maximum values of the inversion strength were 20°C in 200 m altitude difference. In summer (June to August) inversions occur relatively seldom. For the rest of the year, inversions are normally established at night, but are destroyed by day.

The strength of the inversion was analyzed and shown graphically as a function of different independent meteorological parameters for the four seasons and annually. Although there are some differences depending on the season, the strength of the inversions was observed to increase with a) negative net radiation, b) decreasing cloudiness, and c) decreasing windspeed. Furthermore, during the winter a northerly wind direction, probably of orographic origin, was associated with stronger inversions. Such graphical data for a typical subarctic community should be useful in local forecasting and pollution control planning.

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