Some Radar Measurements of Turbulence in Snow

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  • 1 Cornell Aeronautical Laboratory, Inc., Buffalo, N.Y.
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Abstract

The Doppler spectrum of snow contains information about the turbulent wind field in which the snow is embedded. The average spread of the spectrum is proportional to the kinetic energy per unit mass of air in turbulent eddies that are generally smaller than the radar-sampled volume. The time variations in the mean value of velocity in the Doppler spectrum can be analyzed to determine the kinetic energy in eddies that are larger than the sampled volume. Thus from the time behavior of Doppler signals from snow can be estimated the total turbulent energy and the partitioning of this energy between large and small scales.

Root-mean-square turbulent velocities computed on the basis of this technique were found to range between 0.4 and 2 m sec−1, with most of the values less than 1 m sec−1. Approximately three-quarters of the energy is usually in wavelengths shorter than 100 m. The data on the partitioning of eddy energy show considerable scatter, but there is some resemblance to the relationship expected from a Kolmogorov spectral law.

Abstract

The Doppler spectrum of snow contains information about the turbulent wind field in which the snow is embedded. The average spread of the spectrum is proportional to the kinetic energy per unit mass of air in turbulent eddies that are generally smaller than the radar-sampled volume. The time variations in the mean value of velocity in the Doppler spectrum can be analyzed to determine the kinetic energy in eddies that are larger than the sampled volume. Thus from the time behavior of Doppler signals from snow can be estimated the total turbulent energy and the partitioning of this energy between large and small scales.

Root-mean-square turbulent velocities computed on the basis of this technique were found to range between 0.4 and 2 m sec−1, with most of the values less than 1 m sec−1. Approximately three-quarters of the energy is usually in wavelengths shorter than 100 m. The data on the partitioning of eddy energy show considerable scatter, but there is some resemblance to the relationship expected from a Kolmogorov spectral law.

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