Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign
<p>This paper examines the mechanisms responsible for the production of ice in convective clouds influenced by mineral dust. Observations were made in the Ice in Clouds Experiment – Dust (ICE-D) field campaign which took place in the vicinity of Cape Verde during August 2015. Measurements mad...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/1649/2022/acp-22-1649-2022.pdf |
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| author | Z. Cui A. Blyth A. Blyth Y. Huang G. Lloyd G. Lloyd T. Choularton K. Bower P. Field P. Field R. Hawker L. Bennett |
| author_facet | Z. Cui A. Blyth A. Blyth Y. Huang G. Lloyd G. Lloyd T. Choularton K. Bower P. Field P. Field R. Hawker L. Bennett |
| author_sort | Z. Cui |
| collection | DOAJ |
| description | <p>This paper examines the mechanisms responsible for the production of ice in convective clouds influenced by mineral dust. Observations were made in the Ice in Clouds Experiment – Dust (ICE-D) field campaign which took place in the vicinity of Cape Verde during August 2015. Measurements made with instruments on the Facility for Airborne Atmospheric Measurements (FAAM) aircraft through the clouds on 21 August showed that ice particles were observed in high concentrations at temperatures greater than about <span class="inline-formula">−8</span> <span class="inline-formula"><sup>∘</sup></span>C. Sensitivity studies were performed using existing parameterization schemes in a cloud model to explore the impact of the freezing onset temperature, the efficiency of freezing, mineral dust as efficient ice nuclei, and multi-thermals on secondary ice production by the rime-splintering process.</p>
<p>The simulation with the default Morrison microphysics scheme <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx58">Morrison et al.</a>, <a href="#bib1.bibx58">2005</a>)</span> that involved a single thermal produced a concentration of secondary ice that was much lower than the observed value of total ice number concentration. Relaxing the onset temperature to a higher value, enhancing the freezing efficiency, or combinations of these increased the secondary ice particle concentration but not by a sufficient amount. Simulations that involved only dust particles as ice-nucleating particles produced a lower concentration of secondary ice particles, since the freezing onset temperature is low. The simulations implicate that a higher concentration of ice-nucleating particles with a higher freezing onset temperature may explain some of the observed high concentrations of secondary ice. However, a simulation with two thermals that used the original Morrison scheme without enhancement of the freezing efficiency or relaxation of the onset temperature produced the greatest concentration of secondary ice particles. It did so because of the increased time that graupel particles were exposed to significant cloud liquid water in the Hallett–Mossop temperature zone. The forward-facing camera and measurements of the vertical wind in repeated passes of the same cloud suggested that these tropical clouds contained multiple thermals. It is possible of course that several mechanisms, some of them only recently discovered, may be responsible for producing the ice particles in clouds. This study highlights the fact that the dynamics of the clouds likely play an important role in producing high concentrations of secondary ice particles in clouds.</p> |
| first_indexed | 2024-04-11T17:33:53Z |
| format | Article |
| id | doaj.art-d6d652b007dc47b0ac41866431eaf7c8 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-11T17:33:53Z |
| publishDate | 2022-02-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-d6d652b007dc47b0ac41866431eaf7c82022-12-22T04:11:56ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242022-02-01221649166710.5194/acp-22-1649-2022Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaignZ. Cui0A. Blyth1A. Blyth2Y. Huang3G. Lloyd4G. Lloyd5T. Choularton6K. Bower7P. Field8P. Field9R. Hawker10L. Bennett11Institute for Climate and Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UKInstitute for Climate and Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UKNational Centre for Atmospheric Science, Leeds, LS2 9PH, UKInstitute for Climate and Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UKNational Centre for Atmospheric Science, Leeds, LS2 9PH, UKCentre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UKCentre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UKCentre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UKInstitute for Climate and Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UKMet Office, Exeter, EX1 3PB, UKInstitute for Climate and Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UKNational Centre for Atmospheric Science, Leeds, LS2 9PH, UK<p>This paper examines the mechanisms responsible for the production of ice in convective clouds influenced by mineral dust. Observations were made in the Ice in Clouds Experiment – Dust (ICE-D) field campaign which took place in the vicinity of Cape Verde during August 2015. Measurements made with instruments on the Facility for Airborne Atmospheric Measurements (FAAM) aircraft through the clouds on 21 August showed that ice particles were observed in high concentrations at temperatures greater than about <span class="inline-formula">−8</span> <span class="inline-formula"><sup>∘</sup></span>C. Sensitivity studies were performed using existing parameterization schemes in a cloud model to explore the impact of the freezing onset temperature, the efficiency of freezing, mineral dust as efficient ice nuclei, and multi-thermals on secondary ice production by the rime-splintering process.</p> <p>The simulation with the default Morrison microphysics scheme <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx58">Morrison et al.</a>, <a href="#bib1.bibx58">2005</a>)</span> that involved a single thermal produced a concentration of secondary ice that was much lower than the observed value of total ice number concentration. Relaxing the onset temperature to a higher value, enhancing the freezing efficiency, or combinations of these increased the secondary ice particle concentration but not by a sufficient amount. Simulations that involved only dust particles as ice-nucleating particles produced a lower concentration of secondary ice particles, since the freezing onset temperature is low. The simulations implicate that a higher concentration of ice-nucleating particles with a higher freezing onset temperature may explain some of the observed high concentrations of secondary ice. However, a simulation with two thermals that used the original Morrison scheme without enhancement of the freezing efficiency or relaxation of the onset temperature produced the greatest concentration of secondary ice particles. It did so because of the increased time that graupel particles were exposed to significant cloud liquid water in the Hallett–Mossop temperature zone. The forward-facing camera and measurements of the vertical wind in repeated passes of the same cloud suggested that these tropical clouds contained multiple thermals. It is possible of course that several mechanisms, some of them only recently discovered, may be responsible for producing the ice particles in clouds. This study highlights the fact that the dynamics of the clouds likely play an important role in producing high concentrations of secondary ice particles in clouds.</p>https://acp.copernicus.org/articles/22/1649/2022/acp-22-1649-2022.pdf |
| spellingShingle | Z. Cui A. Blyth A. Blyth Y. Huang G. Lloyd G. Lloyd T. Choularton K. Bower P. Field P. Field R. Hawker L. Bennett Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign Atmospheric Chemistry and Physics |
| title | Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign |
| title_full | Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign |
| title_fullStr | Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign |
| title_full_unstemmed | Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign |
| title_short | Multi-thermals and high concentrations of secondary ice: a modelling study of convective clouds during the Ice in Clouds Experiment – Dust (ICE-D) campaign |
| title_sort | multi thermals and high concentrations of secondary ice a modelling study of convective clouds during the ice in clouds experiment dust ice d campaign |
| url | https://acp.copernicus.org/articles/22/1649/2022/acp-22-1649-2022.pdf |
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