Winter Albedo Characteristics at St. Paul, Minnesota

Abstract

Mean and median daily albedos of the November-April period are presented for a nonforested station in the North Central region of the United States where frozen soil and persistent snow cover are common winter features. Three distinct albedo periods were found, the occurrence of which can be explained by comparison with associated daily records of air temperature and snow depth. These periods are: I) Introduction to Winter, 9?22 November, a transitional period in which snowfalls begin to occur but with insufficient frequency or duration to greatly alter the mean albedo from growing season values; II) the High Albedo Season, 23 November?17 March, that is characterized by mean and median albedos of 50% or higher and by a negatively skewed distribution of albedo values in contrast to periods I and III; and III) the transition period, Introduction to Spring, 18 March?12 April, where late season snowfalls of brief duration occur, but the mean albedo is lower than in period I because of the more common occurrence of moist surfaces due to snowmelt and rains.