The n-factor in natural landscaper: Variability of air and soil-surface temperatures, Kuparuk River basin, Alaska, USA

The n-factor, or ratio of the seasonal degree-day sum at the soil surface t o that in the air at standard screen height, has been used for more than 40 yr in engineering studies to parameterize the temperature regime at the gr ound surface. Conceptually, this index represents the complex energy balanc e at the surface as a single dimensionless number and has applications in e cology, climatology, and geocryology. Although the n-factor has been used t heoretically to represent the thermal regime of undisturbed natural surface s, lack of empirical data has hindered its widespread implementation. Nine ground and one air temperature series (1995-97) from each of ten 1-ha plots on the coastal plain and Brooks Range foothills of north-central Alaska we re converted to thawing (summer) n-factors and analyzed to address within- and between-plot spatial and temporal variability. Although substantial mic roscale variation exists, n-factors corresponding to natural vegetation/soi l classes are discernable. Incorporation of n-factor values in a standard s olution for the depth of thaw resulted in significantly improved estimates of active-layer thickness throughout the study area. The n-factor has consi derable potential for addressing problems involving near-surface climate dy namics over extensive regions and long time periods.