Radiation Climate of Barrow Alaska, 1962–66

Gary A. Maykut Dept. of Atmospheric Sciences, University of Washington, Seattle 98195

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Phil E. Church Dept. of Atmospheric Sciences, University of Washington, Seattle 98195

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Abstract

Observations of the radiation climate near Point Barrow, Alaska, were conducted during a five-year period between 1962 and 1966. Data on incoming shortwave radiation, albedo, incoming longwave radiation, and net total radiation are summarized in the form of monthly and annual averages. Due to the prevalence of summer clouds, incident shortwave radiation (Q) reaches a peak in early June with maximum flux values in excess of 50 mW cm−3. Increasing cloud cover throughout the snow-free period results in a distribution for Q which is asymmetric about the summer solstice. Atmospheric transmissivity averages vary between 34% in late summer and 69% in late winter, the annual average being 51%. The albedo regime exhibits four distinctly different parts: 1) a winter stationary period, 2) a spring transitional period, 3) a summer stationary period, and 4) an autumn transitional period. Incoming longwave radiation (E) averages 24 mW cm−2 for the year with a seasonal variation of around 7 mW cm−2 year−1. On an annual basis, the surface receives more than twice as much longwave as shortwave radiation (744 vs 320 kJ cm−1). The data indicate that E can be calculated from the empirical relationship.where T is the air temperature at screen height and G is the cloudiness in tenths. Using this formula, the standard deviation of the percent difference between the observed and predicted values of E is 9%. Net total radiation (B) over the tundra averages 45 kJ cm−2 year−1; the annual total is critically dependent upon the date of snow melt. Bemuse of the lower summer albedos, the numerous lakes in the region have annual B values which are 25% larger than those over the tundra, resulting in an integrated average for the Barrow area of about 50 kJ cm−2 year−1. On the basis of this study it appears that with routine data from the Barrow Weather Station, together with supplemental snow cover data, the components of the radiation balance along the coastal portions. of the Alaskan North Slope can be estimated with an accuracy that may be sufficient for many biological and engineering applications.

Abstract

Observations of the radiation climate near Point Barrow, Alaska, were conducted during a five-year period between 1962 and 1966. Data on incoming shortwave radiation, albedo, incoming longwave radiation, and net total radiation are summarized in the form of monthly and annual averages. Due to the prevalence of summer clouds, incident shortwave radiation (Q) reaches a peak in early June with maximum flux values in excess of 50 mW cm−3. Increasing cloud cover throughout the snow-free period results in a distribution for Q which is asymmetric about the summer solstice. Atmospheric transmissivity averages vary between 34% in late summer and 69% in late winter, the annual average being 51%. The albedo regime exhibits four distinctly different parts: 1) a winter stationary period, 2) a spring transitional period, 3) a summer stationary period, and 4) an autumn transitional period. Incoming longwave radiation (E) averages 24 mW cm−2 for the year with a seasonal variation of around 7 mW cm−2 year−1. On an annual basis, the surface receives more than twice as much longwave as shortwave radiation (744 vs 320 kJ cm−1). The data indicate that E can be calculated from the empirical relationship.where T is the air temperature at screen height and G is the cloudiness in tenths. Using this formula, the standard deviation of the percent difference between the observed and predicted values of E is 9%. Net total radiation (B) over the tundra averages 45 kJ cm−2 year−1; the annual total is critically dependent upon the date of snow melt. Bemuse of the lower summer albedos, the numerous lakes in the region have annual B values which are 25% larger than those over the tundra, resulting in an integrated average for the Barrow area of about 50 kJ cm−2 year−1. On the basis of this study it appears that with routine data from the Barrow Weather Station, together with supplemental snow cover data, the components of the radiation balance along the coastal portions. of the Alaskan North Slope can be estimated with an accuracy that may be sufficient for many biological and engineering applications.

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