Micrometeorological Conditions for Dust-Devil Occurrence in the Atacama Desert |
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Authors: | Michael V Kurgansky Aldo Montecinos Victor Villagran Stephen M Metzger |
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Institution: | (1) Centre for Research in Earth and Space Science, York University, Toronto, ON, Canada |
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Abstract: | We report on field observations in January 2009 (austral summer) of atmospheric dust devils in the northern part of the Atacama
Desert in South America (≈20◦S). An extremely high level of dust-devil activity over the study site has been observed, dependent on local meteorological
conditions. We found a high correlation between the dust-devil frequency of occurrence and the Obukhov length scale, L, calculated from meteorological gradient measurements, with a clear tendency for this frequency to increase with decreasing
−L. The upper threshold values of −L ≈ 20–30 m, and the 2-m mean wind speed, V
2 ≈ 8m s−1, for dust-devil occurrence have been found, but the minimal V
2 threshold was not observed. Parallel routine meteorological measurements enabled us to calculate the main constituents of
the surface energy balance, to obtain direct estimates of the surface albedo (α ≈ 0.21 at the solar noon) and to summarize the local conditions. |
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