Some Instances of Unstable Surface Temperature Conditions During an Arctic Winter

Unstable conditions (in which air temperature decreases with increasing height at more than 1 C per 100 m) were recorded (to height of 30 m) at Eielson Air Force Base near Fairbanks, Alaska, during Jan.-Feb. 1954, as part of Alaska ice fog investigations. Weather conditions producing surface instability are (in order of importance in the Arctic): periods of strong insolation when snow surface is in bright sun; periods of heavy overcast with an over-riding warm air mass; periods of ice fog. Observations of each condition are discussed; also frequencies at which various lapse rate conditions occurred at low levels in Jan.-Feb. Instability due to ice fog is of minor importance in arctic climatology generally, as ice fog and its associated lapse rates are restricted to urban areas.