Anomalous Behavior of the Atmospheric Surface Layer over a Melting Snowpack

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  • 1 Jet Propulsion Laboratory, Pasadena, CA 91103
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Abstract

During March, 1978 on a snow-covered field near Lee Vining, California, measurements were made that included: 1) variations above the snow surface of the net radiative flux and the profile of wind speed, air temperature and relative humidity; and 2) variations beneath the snow surface of the conductive heat flux and the temperature profile. The period was marked by clear skies, warm air and calm winds during the day, and cold air and moderate winds at night. During the day, a highly stable sublayer formed near the surface, with a persistent warm layer at ∼0.5 m above the surface. At night, profiles agreed more with classical log-linear forms found in stable air. Numerical simulation of long and shortwave radiative fluxes near the surface, using observed humidity profiles, produced the daytime warm level in agreement with observations. It was concluded that in the absence of turbulent mixing, strong solar radiation and a supply of moisture from the snow will cause a raised maximum of temperature during the day.

Abstract

During March, 1978 on a snow-covered field near Lee Vining, California, measurements were made that included: 1) variations above the snow surface of the net radiative flux and the profile of wind speed, air temperature and relative humidity; and 2) variations beneath the snow surface of the conductive heat flux and the temperature profile. The period was marked by clear skies, warm air and calm winds during the day, and cold air and moderate winds at night. During the day, a highly stable sublayer formed near the surface, with a persistent warm layer at ∼0.5 m above the surface. At night, profiles agreed more with classical log-linear forms found in stable air. Numerical simulation of long and shortwave radiative fluxes near the surface, using observed humidity profiles, produced the daytime warm level in agreement with observations. It was concluded that in the absence of turbulent mixing, strong solar radiation and a supply of moisture from the snow will cause a raised maximum of temperature during the day.

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