What can we conclude about the real aspect ratios of ice particle aggregates from two-dimensional images?

Zhiyuan Jiang, Mariko Oue, Johannes Verlinde, Eugene E. Clothiaux, Kultegin Aydin, Giovanni Botta, Yinghui Lu

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

A simple numerical experiment was performed to investigate the result published in many papers that measurements indicate that aggregates may be well represented as oblate spheroids with mean aspect ratio (semiminor axis to semimajor axis length) of 0.6. The aspect ratio measurements are derived from two-dimensional projections of complex three-dimensional aggregates. Here, aggregates were modeled as ellipsoids with semiprincipal axes of length a, b, and c, which include oblate spheroids (a = b) as a class, and the projected aspect ratios of large numbers of two-dimensional projections of them were sampled. When sampling oblate spheroids with aspect ratio 0.6 over random orientations, the mean projected aspect ratio is 0.746. A mean projected aspect ratio of 0.6 is obtained for an oblate spheroid with aspect ratio of 0.33. When sampling randomly oriented ellipsoids with semiminor axes (b, c) varying from 0.10 to 1.00 in steps of 0.01, representing many complex shapes, the mean projected aspect ratio is 0.595, close to the measured mean projected aspect ratio of aggregates of 0.6. These experiments demonstrate that the conclusion one may safely draw from the projected aspect ratio measurements is that the mean aspect ratio of aggregates is lower than 0.6. Moreover, the projected aspect ratio distributions from measurements suggest a mixture of aggregate shapes, rather than only oblate spheroids as is often assumed.

Original languageEnglish (US)
Pages (from-to)725-734
Number of pages10
JournalJournal of Applied Meteorology and Climatology
Volume56
Issue number3
DOIs
StatePublished - Jan 1 2017

Fingerprint

ice
sampling
particle
experiment

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

@article{50901a2cad4446fea41aaf80bb10808d,
title = "What can we conclude about the real aspect ratios of ice particle aggregates from two-dimensional images?",
abstract = "A simple numerical experiment was performed to investigate the result published in many papers that measurements indicate that aggregates may be well represented as oblate spheroids with mean aspect ratio (semiminor axis to semimajor axis length) of 0.6. The aspect ratio measurements are derived from two-dimensional projections of complex three-dimensional aggregates. Here, aggregates were modeled as ellipsoids with semiprincipal axes of length a, b, and c, which include oblate spheroids (a = b) as a class, and the projected aspect ratios of large numbers of two-dimensional projections of them were sampled. When sampling oblate spheroids with aspect ratio 0.6 over random orientations, the mean projected aspect ratio is 0.746. A mean projected aspect ratio of 0.6 is obtained for an oblate spheroid with aspect ratio of 0.33. When sampling randomly oriented ellipsoids with semiminor axes (b, c) varying from 0.10 to 1.00 in steps of 0.01, representing many complex shapes, the mean projected aspect ratio is 0.595, close to the measured mean projected aspect ratio of aggregates of 0.6. These experiments demonstrate that the conclusion one may safely draw from the projected aspect ratio measurements is that the mean aspect ratio of aggregates is lower than 0.6. Moreover, the projected aspect ratio distributions from measurements suggest a mixture of aggregate shapes, rather than only oblate spheroids as is often assumed.",
author = "Zhiyuan Jiang and Mariko Oue and Johannes Verlinde and Clothiaux, {Eugene E.} and Kultegin Aydin and Giovanni Botta and Yinghui Lu",
year = "2017",
month = "1",
day = "1",
doi = "10.1175/JAMC-D-16-0248.1",
language = "English (US)",
volume = "56",
pages = "725--734",
journal = "Journal of Applied Meteorology and Climatology",
issn = "1558-8424",
publisher = "American Meteorological Society",
number = "3",

}

TY - JOUR

T1 - What can we conclude about the real aspect ratios of ice particle aggregates from two-dimensional images?

AU - Jiang, Zhiyuan

AU - Oue, Mariko

AU - Verlinde, Johannes

AU - Clothiaux, Eugene E.

AU - Aydin, Kultegin

AU - Botta, Giovanni

AU - Lu, Yinghui

PY - 2017/1/1

Y1 - 2017/1/1

N2 - A simple numerical experiment was performed to investigate the result published in many papers that measurements indicate that aggregates may be well represented as oblate spheroids with mean aspect ratio (semiminor axis to semimajor axis length) of 0.6. The aspect ratio measurements are derived from two-dimensional projections of complex three-dimensional aggregates. Here, aggregates were modeled as ellipsoids with semiprincipal axes of length a, b, and c, which include oblate spheroids (a = b) as a class, and the projected aspect ratios of large numbers of two-dimensional projections of them were sampled. When sampling oblate spheroids with aspect ratio 0.6 over random orientations, the mean projected aspect ratio is 0.746. A mean projected aspect ratio of 0.6 is obtained for an oblate spheroid with aspect ratio of 0.33. When sampling randomly oriented ellipsoids with semiminor axes (b, c) varying from 0.10 to 1.00 in steps of 0.01, representing many complex shapes, the mean projected aspect ratio is 0.595, close to the measured mean projected aspect ratio of aggregates of 0.6. These experiments demonstrate that the conclusion one may safely draw from the projected aspect ratio measurements is that the mean aspect ratio of aggregates is lower than 0.6. Moreover, the projected aspect ratio distributions from measurements suggest a mixture of aggregate shapes, rather than only oblate spheroids as is often assumed.

AB - A simple numerical experiment was performed to investigate the result published in many papers that measurements indicate that aggregates may be well represented as oblate spheroids with mean aspect ratio (semiminor axis to semimajor axis length) of 0.6. The aspect ratio measurements are derived from two-dimensional projections of complex three-dimensional aggregates. Here, aggregates were modeled as ellipsoids with semiprincipal axes of length a, b, and c, which include oblate spheroids (a = b) as a class, and the projected aspect ratios of large numbers of two-dimensional projections of them were sampled. When sampling oblate spheroids with aspect ratio 0.6 over random orientations, the mean projected aspect ratio is 0.746. A mean projected aspect ratio of 0.6 is obtained for an oblate spheroid with aspect ratio of 0.33. When sampling randomly oriented ellipsoids with semiminor axes (b, c) varying from 0.10 to 1.00 in steps of 0.01, representing many complex shapes, the mean projected aspect ratio is 0.595, close to the measured mean projected aspect ratio of aggregates of 0.6. These experiments demonstrate that the conclusion one may safely draw from the projected aspect ratio measurements is that the mean aspect ratio of aggregates is lower than 0.6. Moreover, the projected aspect ratio distributions from measurements suggest a mixture of aggregate shapes, rather than only oblate spheroids as is often assumed.

UR - http://www.scopus.com/inward/record.url?scp=85015256788&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85015256788&partnerID=8YFLogxK

U2 - 10.1175/JAMC-D-16-0248.1

DO - 10.1175/JAMC-D-16-0248.1

M3 - Article

AN - SCOPUS:85015256788

VL - 56

SP - 725

EP - 734

JO - Journal of Applied Meteorology and Climatology

JF - Journal of Applied Meteorology and Climatology

SN - 1558-8424

IS - 3

ER -