Microphysical characteristics of frozen droplet aggregates from deep convective clouds
<p>During the 2012 Deep Convective Clouds and Chemistry (DC3) experiment the National Science Foundation/National Center for Atmospheric Research Gulfstream V (GV) aircraft sampled the upper anvils of two storms that developed in eastern Colorado on 6 June 2012. A cloud particle imager (CPI) m...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/16915/2018/acp-18-16915-2018.pdf |
| _version_ | 1819098404498702336 |
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| author | J. Um J. Um G. M. McFarquhar G. M. McFarquhar G. M. McFarquhar J. L. Stith C. H. Jung S. S. Lee J. Y. Lee Y. Shin Y. G. Lee Y. I. Yang S. S. Yum B.-G. Kim J. W. Cha A.-R. Ko |
| author_facet | J. Um J. Um G. M. McFarquhar G. M. McFarquhar G. M. McFarquhar J. L. Stith C. H. Jung S. S. Lee J. Y. Lee Y. Shin Y. G. Lee Y. I. Yang S. S. Yum B.-G. Kim J. W. Cha A.-R. Ko |
| author_sort | J. Um |
| collection | DOAJ |
| description | <p>During the 2012 Deep Convective Clouds and Chemistry
(DC3) experiment the National Science Foundation/National Center for
Atmospheric Research Gulfstream V (GV) aircraft sampled the upper anvils of
two storms that developed in eastern Colorado on 6 June 2012. A cloud
particle imager (CPI) mounted on the GV aircraft recorded images of ice
crystals at altitudes of 12.0 to 12.4 km and temperatures (<span class="inline-formula"><i>T</i></span>) from <span class="inline-formula">−61</span> to <span class="inline-formula">−</span>55 <span class="inline-formula"><sup>∘</sup></span>C.
A total of 22 393 CPI crystal images were analyzed, all with maximum
dimension (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>D</mi><mo>max</mo></msub><mo>)</mo><mo><</mo><mn mathvariant="normal">433</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="60pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1fec6f0a893bea878a52c005deb30b1b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16915-2018-ie00001.svg" width="60pt" height="13pt" src="acp-18-16915-2018-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">µ</span>m and with an average <span class="inline-formula"><i>D</i><sub>max</sub></span> of
<span class="inline-formula">80.7±45.4</span> <span class="inline-formula">µ</span>m. The occurrence of well-defined pristine crystals
(e.g., columns and plates) was less than 0.04 % by number. Single frozen
droplets and frozen droplet aggregates (FDAs) were the dominant habits with
fractions of 73.0 % (by number) and 46.3 % (by projected area),
respectively. The relative frequency of occurrence of single frozen droplets
and FDAs depended on temperature and position within the anvil cloud.</p>
<p>A new algorithm that uses the circle Hough transform technique was developed
to automatically identify the number, size, and relative position of element
frozen droplets within FDAs. Of the FDAs, 42.0 % had two element frozen
droplets with an average of <span class="inline-formula">4.7±5.0</span> element frozen droplets. The
frequency of occurrence gradually decreased with the number of element frozen
droplets. Based on the number, size, and relative position of the element
frozen droplets within the FDAs, possible three-dimensional (3-D)
realizations of FDAs were generated and characterized by two different shape
parameters, the aggregation index (AI) and the fractal dimension (<span class="inline-formula"><i>D</i><sub>f</sub></span>),
that describe 3-D shapes and link to scattering properties with an
assumption of spherical shape of element frozen droplets. The AI of FDAs
decreased with an increase in the number of element frozen droplets, with
larger FDAs with more element frozen droplets having more compact shapes.
The <span class="inline-formula"><i>D</i><sub>f</sub></span> of FDAs was about 1.20–1.43 smaller than that of black carbon
(BC) aggregates (1.53–1.85) determined in previous studies. Such a smaller
<span class="inline-formula"><i>D</i><sub>f</sub></span> of FDAs indicates that FDAs have more linear chain-like branched
shapes than the compact shapes of BC aggregates. Determined morphological
characteristics of FDAs along with the proposed reconstructed 3-D
representations of FDAs<span id="page16916"/> in this study have important implications for
improving the calculations of the microphysical (e.g., fall velocity) and radiative
(e.g., asymmetry parameter) properties of ice crystals in upper anvil
clouds.</p> |
| first_indexed | 2024-12-22T00:30:27Z |
| format | Article |
| id | doaj.art-04d6529d606348c9adbdd256517c7e6b |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-22T00:30:27Z |
| publishDate | 2018-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-04d6529d606348c9adbdd256517c7e6b2022-12-21T18:44:56ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-11-0118169151693010.5194/acp-18-16915-2018Microphysical characteristics of frozen droplet aggregates from deep convective cloudsJ. Um0J. Um1G. M. McFarquhar2G. M. McFarquhar3G. M. McFarquhar4J. L. Stith5C. H. Jung6S. S. Lee7J. Y. Lee8Y. Shin9Y. G. Lee10Y. I. Yang11S. S. Yum12B.-G. Kim13J. W. Cha14A.-R. Ko15Department of Atmospheric Sciences, Pusan National University, Busan, South KoreaCooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma, USACooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma, USASchool of Meteorology, University of Oklahoma, Norman, Oklahoma, USANational Center for Atmospheric Research, Boulder, Colorado, USANational Center for Atmospheric Research, Boulder, Colorado, USADepartment of Health Management, Kyungin Women's University, Incheon, South KoreaEarth System Science Interdisciplinary Center, College Park, Maryland, USADepartment of Environmental Science and Engineering, Ewha Womans University, Seoul, South KoreaDepartment of Agricultural and Biological Engineering, University of Illinois, Urbana, Illinois, USADepartment of Atmospheric Sciences, Chungnam National University, Daejeon, South KoreaDepartment of Atmospheric Sciences, Yonsei University, Seoul, South KoreaDepartment of Atmospheric Sciences, Yonsei University, Seoul, South KoreaDepartment of Atmospheric and Environmental Sciences, Gangneung-Wonju National University, Gangneung, South KoreaApplied Meteorology Research Division, National Institute of Meteorological Sciences, Jeju, South KoreaApplied Meteorology Research Division, National Institute of Meteorological Sciences, Jeju, South Korea<p>During the 2012 Deep Convective Clouds and Chemistry (DC3) experiment the National Science Foundation/National Center for Atmospheric Research Gulfstream V (GV) aircraft sampled the upper anvils of two storms that developed in eastern Colorado on 6 June 2012. A cloud particle imager (CPI) mounted on the GV aircraft recorded images of ice crystals at altitudes of 12.0 to 12.4 km and temperatures (<span class="inline-formula"><i>T</i></span>) from <span class="inline-formula">−61</span> to <span class="inline-formula">−</span>55 <span class="inline-formula"><sup>∘</sup></span>C. A total of 22 393 CPI crystal images were analyzed, all with maximum dimension (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>D</mi><mo>max</mo></msub><mo>)</mo><mo><</mo><mn mathvariant="normal">433</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="60pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1fec6f0a893bea878a52c005deb30b1b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-18-16915-2018-ie00001.svg" width="60pt" height="13pt" src="acp-18-16915-2018-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">µ</span>m and with an average <span class="inline-formula"><i>D</i><sub>max</sub></span> of <span class="inline-formula">80.7±45.4</span> <span class="inline-formula">µ</span>m. The occurrence of well-defined pristine crystals (e.g., columns and plates) was less than 0.04 % by number. Single frozen droplets and frozen droplet aggregates (FDAs) were the dominant habits with fractions of 73.0 % (by number) and 46.3 % (by projected area), respectively. The relative frequency of occurrence of single frozen droplets and FDAs depended on temperature and position within the anvil cloud.</p> <p>A new algorithm that uses the circle Hough transform technique was developed to automatically identify the number, size, and relative position of element frozen droplets within FDAs. Of the FDAs, 42.0 % had two element frozen droplets with an average of <span class="inline-formula">4.7±5.0</span> element frozen droplets. The frequency of occurrence gradually decreased with the number of element frozen droplets. Based on the number, size, and relative position of the element frozen droplets within the FDAs, possible three-dimensional (3-D) realizations of FDAs were generated and characterized by two different shape parameters, the aggregation index (AI) and the fractal dimension (<span class="inline-formula"><i>D</i><sub>f</sub></span>), that describe 3-D shapes and link to scattering properties with an assumption of spherical shape of element frozen droplets. The AI of FDAs decreased with an increase in the number of element frozen droplets, with larger FDAs with more element frozen droplets having more compact shapes. The <span class="inline-formula"><i>D</i><sub>f</sub></span> of FDAs was about 1.20–1.43 smaller than that of black carbon (BC) aggregates (1.53–1.85) determined in previous studies. Such a smaller <span class="inline-formula"><i>D</i><sub>f</sub></span> of FDAs indicates that FDAs have more linear chain-like branched shapes than the compact shapes of BC aggregates. Determined morphological characteristics of FDAs along with the proposed reconstructed 3-D representations of FDAs<span id="page16916"/> in this study have important implications for improving the calculations of the microphysical (e.g., fall velocity) and radiative (e.g., asymmetry parameter) properties of ice crystals in upper anvil clouds.</p>https://www.atmos-chem-phys.net/18/16915/2018/acp-18-16915-2018.pdf |
| spellingShingle | J. Um J. Um G. M. McFarquhar G. M. McFarquhar G. M. McFarquhar J. L. Stith C. H. Jung S. S. Lee J. Y. Lee Y. Shin Y. G. Lee Y. I. Yang S. S. Yum B.-G. Kim J. W. Cha A.-R. Ko Microphysical characteristics of frozen droplet aggregates from deep convective clouds Atmospheric Chemistry and Physics |
| title | Microphysical characteristics of frozen droplet aggregates from deep convective clouds |
| title_full | Microphysical characteristics of frozen droplet aggregates from deep convective clouds |
| title_fullStr | Microphysical characteristics of frozen droplet aggregates from deep convective clouds |
| title_full_unstemmed | Microphysical characteristics of frozen droplet aggregates from deep convective clouds |
| title_short | Microphysical characteristics of frozen droplet aggregates from deep convective clouds |
| title_sort | microphysical characteristics of frozen droplet aggregates from deep convective clouds |
| url | https://www.atmos-chem-phys.net/18/16915/2018/acp-18-16915-2018.pdf |
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