Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds
<p>Condensational growth of cloud droplets due to supersaturation fluctuations is investigated by solving the hydrodynamic and thermodynamic equations using direct numerical simulations (DNS) with droplets being modeled as Lagrangian particles. The supersaturation field is calculated directly...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2019-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/639/2019/acp-19-639-2019.pdf |
| _version_ | 1818015947571593216 |
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| author | X.-Y. Li X.-Y. Li X.-Y. Li X.-Y. Li X.-Y. Li G. Svensson G. Svensson G. Svensson A. Brandenburg A. Brandenburg A. Brandenburg A. Brandenburg N. E. L. Haugen N. E. L. Haugen |
| author_facet | X.-Y. Li X.-Y. Li X.-Y. Li X.-Y. Li X.-Y. Li G. Svensson G. Svensson G. Svensson A. Brandenburg A. Brandenburg A. Brandenburg A. Brandenburg N. E. L. Haugen N. E. L. Haugen |
| author_sort | X.-Y. Li |
| collection | DOAJ |
| description | <p>Condensational growth of cloud droplets due to supersaturation fluctuations
is investigated by solving the hydrodynamic and thermodynamic equations using
direct numerical simulations (DNS) with droplets being modeled as Lagrangian
particles. The supersaturation field is calculated directly by simulating the
temperature and water vapor fields instead of being treated as a passive
scalar. Thermodynamic feedbacks to the fields due to condensation are also
included for completeness. We find that the width of droplet size
distributions increases with time, which is contrary to the classical theory
without supersaturation fluctuations, where condensational growth leads to
progressively narrower size distributions. Nevertheless, in agreement with
earlier Lagrangian stochastic models of the condensational growth, the
standard deviation of the surface area of droplets increases as <span class="inline-formula"><i>t</i><sup>1∕2</sup></span>.
Also, for the first time, we explicitly demonstrate that the time evolution
of the size distribution is sensitive to the Reynolds number, but insensitive
to the mean energy dissipation rate. This is shown to be due to the fact that
temperature fluctuations and water vapor mixing ratio fluctuations increase
with increasing Reynolds number; therefore the resulting supersaturation
fluctuations are enhanced with increasing Reynolds number. Our simulations
may explain the broadening of the size distribution in stratiform clouds
qualitatively, where the mean updraft velocity is almost zero.</p> |
| first_indexed | 2024-04-14T07:05:03Z |
| format | Article |
| id | doaj.art-bc8787475d584ebf9fbda3923e936968 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-14T07:05:03Z |
| publishDate | 2019-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-bc8787475d584ebf9fbda3923e9369682022-12-22T02:06:35ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-01-011963964810.5194/acp-19-639-2019Cloud-droplet growth due to supersaturation fluctuations in stratiform cloudsX.-Y. Li0X.-Y. Li1X.-Y. Li2X.-Y. Li3X.-Y. Li4G. Svensson5G. Svensson6G. Svensson7A. Brandenburg8A. Brandenburg9A. Brandenburg10A. Brandenburg11N. E. L. Haugen12N. E. L. Haugen13Department of Meteorology and Bolin Centre for Climate Research, Stockholm University, Stockholm, SwedenNordita, KTH Royal Institute of Technology and Stockholm University, 10691 Stockholm, SwedenSwedish e-Science Research Centre, Stockholm, SwedenLaboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USAJILA, Box 440, University of Colorado, Boulder, CO 80303, USADepartment of Meteorology and Bolin Centre for Climate Research, Stockholm University, Stockholm, SwedenSwedish e-Science Research Centre, Stockholm, SwedenGlobal & Climate Dynamics, National Center for Atmospheric Research, Boulder, CO 80305, USANordita, KTH Royal Institute of Technology and Stockholm University, 10691 Stockholm, SwedenLaboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USAJILA, Box 440, University of Colorado, Boulder, CO 80303, USADepartment of Astronomy, Stockholm University, 10691 Stockholm, SwedenSINTEF Energy Research, 7465 Trondheim, NorwayDepartment of Energy and Process Engineering, NTNU, 7491 Trondheim, Norway<p>Condensational growth of cloud droplets due to supersaturation fluctuations is investigated by solving the hydrodynamic and thermodynamic equations using direct numerical simulations (DNS) with droplets being modeled as Lagrangian particles. The supersaturation field is calculated directly by simulating the temperature and water vapor fields instead of being treated as a passive scalar. Thermodynamic feedbacks to the fields due to condensation are also included for completeness. We find that the width of droplet size distributions increases with time, which is contrary to the classical theory without supersaturation fluctuations, where condensational growth leads to progressively narrower size distributions. Nevertheless, in agreement with earlier Lagrangian stochastic models of the condensational growth, the standard deviation of the surface area of droplets increases as <span class="inline-formula"><i>t</i><sup>1∕2</sup></span>. Also, for the first time, we explicitly demonstrate that the time evolution of the size distribution is sensitive to the Reynolds number, but insensitive to the mean energy dissipation rate. This is shown to be due to the fact that temperature fluctuations and water vapor mixing ratio fluctuations increase with increasing Reynolds number; therefore the resulting supersaturation fluctuations are enhanced with increasing Reynolds number. Our simulations may explain the broadening of the size distribution in stratiform clouds qualitatively, where the mean updraft velocity is almost zero.</p>https://www.atmos-chem-phys.net/19/639/2019/acp-19-639-2019.pdf |
| spellingShingle | X.-Y. Li X.-Y. Li X.-Y. Li X.-Y. Li X.-Y. Li G. Svensson G. Svensson G. Svensson A. Brandenburg A. Brandenburg A. Brandenburg A. Brandenburg N. E. L. Haugen N. E. L. Haugen Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds Atmospheric Chemistry and Physics |
| title | Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds |
| title_full | Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds |
| title_fullStr | Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds |
| title_full_unstemmed | Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds |
| title_short | Cloud-droplet growth due to supersaturation fluctuations in stratiform clouds |
| title_sort | cloud droplet growth due to supersaturation fluctuations in stratiform clouds |
| url | https://www.atmos-chem-phys.net/19/639/2019/acp-19-639-2019.pdf |
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