Geophysical Research Letters

Do all raindrops fall at terminal speed?

Authors

  • Guillermo Montero-Martínez,

    1. Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica, Mexico City, Mexico
    2. Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica, Mexico City, Mexico
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  • Alexander B. Kostinski,

    1. Department of Physics, Michigan Technological University, Houghton, Michigan, USA
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  • Raymond A. Shaw,

    1. Department of Physics, Michigan Technological University, Houghton, Michigan, USA
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  • Fernando García-García

    1. Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica, Mexico City, Mexico
    2. Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica, Mexico City, Mexico
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Abstract

[1] A unique relation between raindrop size and fall speed vt(D) is assumed throughout atmospheric science. Yet, our speed versus size measurements of millions of drops during natural rainfall events show that many intermediate sized raindrops fall up to an order of magnitude faster than expected. Furthermore, images of drop clusters reveal that these “super-terminal drops” are differently sized fragments of a recent break-up, moving with the speed of the parent drop and relaxing towards vt(D). Additional evidence of the break-up conjecture includes: (i) positive skewness in the distribution of fall speed deviations, (ii) strong size dependence of fall speed deviations and their maximum values and, (iii) preponderance of super-terminal drops in the presence of large raindrops (i.e., during periods of high rainfall rates).

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