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Fractal geometry of aggregate snowflakes revealed by triple‐wavelength radar measurements
Author(s) -
Stein T. H. M.,
Westbrook C. D.,
Nicol J. C.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl062170
Subject(s) - snowflake , fractal , fractal dimension , wavelength , radar , aggregate (composite) , scattering , geometry , geology , optics , physics , remote sensing , materials science , mathematics , computer science , meteorology , snow , mathematical analysis , telecommunications , composite material
Radar reflectivity measurements from three different wavelengths are used to retrieve information about the shape of aggregate snowflakes in deep stratiform ice clouds. Dual‐wavelength ratios are calculated for different shape models and compared to observations at 3, 35, and 94 GHz. It is demonstrated that many scattering models, including spherical and spheroidal models, do not adequately describe the aggregate snowflakes that are observed. The observations are consistent with fractal aggregate geometries generated by a physically based aggregation model. It is demonstrated that the fractal dimension of large aggregates can be inferred directly from the radar data. Fractal dimensions close to 2 are retrieved, consistent with previous theoretical models and in situ observations.