Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation
Cloud droplet size distributions (CDSDs), which are related to cloud albedo and rain formation, are usually broader in warm clouds than predicted from adiabatic parcel calculations. We investigate a mechanism for the CDSD broadening using a moving-size-grid cloud parcel model that considers the...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/7313/2018/acp-18-7313-2018.pdf |
| _version_ | 1818267078329630720 |
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| author | F. Yang P. Kollias P. Kollias R. A. Shaw A. M. Vogelmann |
| author_facet | F. Yang P. Kollias P. Kollias R. A. Shaw A. M. Vogelmann |
| author_sort | F. Yang |
| collection | DOAJ |
| description | Cloud droplet size distributions (CDSDs), which are related to cloud albedo
and rain formation, are usually broader in warm clouds than predicted from
adiabatic parcel calculations. We investigate a mechanism for the CDSD
broadening using a moving-size-grid cloud parcel model that considers the
condensational growth of cloud droplets formed on polydisperse,
submicrometer aerosols in an adiabatic cloud parcel that undergoes vertical
oscillations, such as those due to cloud circulations or turbulence. Results
show that the CDSD can be broadened during condensational growth as a result
of Ostwald ripening amplified by droplet deactivation and reactivation, which
is consistent with early work. The relative roles of the solute effect,
curvature effect, deactivation and reactivation on CDSD broadening are
investigated. Deactivation of smaller cloud droplets, which is due to the
combination of curvature and solute effects in the downdraft region, enhances
the growth of larger cloud droplets and thus contributes particles to the
larger size end of the CDSD. Droplet reactivation, which occurs in the
updraft region, contributes particles to the smaller size end of the CDSD. In
addition, we find that growth of the largest cloud droplets strongly depends
on the residence time of cloud droplet in the cloud rather than the magnitude
of local variability in the supersaturation fluctuation. This is because the
environmental saturation ratio is strongly buffered by numerous smaller cloud
droplets. Two necessary conditions for this CDSD broadening, which generally
occur in the atmosphere, are as follows: (1) droplets form on aerosols of different
sizes, and (2) the cloud parcel experiences upwards and downwards motions.
Therefore we expect that this mechanism for CDSD broadening is possible in
real clouds. Our results also suggest it is important to consider both
curvature and solute effects before and after cloud droplet activation in a
cloud model. The importance of this mechanism compared with other mechanisms
on cloud properties should be investigated through in situ measurements and
3-D dynamic models. |
| first_indexed | 2024-12-12T20:16:52Z |
| format | Article |
| id | doaj.art-2af603a4153b46c39e162a5906bec7f8 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T20:16:52Z |
| publishDate | 2018-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-2af603a4153b46c39e162a5906bec7f82022-12-22T00:13:21ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-05-01187313732810.5194/acp-18-7313-2018Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivationF. Yang0P. Kollias1P. Kollias2R. A. Shaw3A. M. Vogelmann4Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, New York, USAEnvironmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, New York, USASchool of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York, USADepartment of Physics, Michigan Technological University, Houghton, Michigan, USAEnvironmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, New York, USACloud droplet size distributions (CDSDs), which are related to cloud albedo and rain formation, are usually broader in warm clouds than predicted from adiabatic parcel calculations. We investigate a mechanism for the CDSD broadening using a moving-size-grid cloud parcel model that considers the condensational growth of cloud droplets formed on polydisperse, submicrometer aerosols in an adiabatic cloud parcel that undergoes vertical oscillations, such as those due to cloud circulations or turbulence. Results show that the CDSD can be broadened during condensational growth as a result of Ostwald ripening amplified by droplet deactivation and reactivation, which is consistent with early work. The relative roles of the solute effect, curvature effect, deactivation and reactivation on CDSD broadening are investigated. Deactivation of smaller cloud droplets, which is due to the combination of curvature and solute effects in the downdraft region, enhances the growth of larger cloud droplets and thus contributes particles to the larger size end of the CDSD. Droplet reactivation, which occurs in the updraft region, contributes particles to the smaller size end of the CDSD. In addition, we find that growth of the largest cloud droplets strongly depends on the residence time of cloud droplet in the cloud rather than the magnitude of local variability in the supersaturation fluctuation. This is because the environmental saturation ratio is strongly buffered by numerous smaller cloud droplets. Two necessary conditions for this CDSD broadening, which generally occur in the atmosphere, are as follows: (1) droplets form on aerosols of different sizes, and (2) the cloud parcel experiences upwards and downwards motions. Therefore we expect that this mechanism for CDSD broadening is possible in real clouds. Our results also suggest it is important to consider both curvature and solute effects before and after cloud droplet activation in a cloud model. The importance of this mechanism compared with other mechanisms on cloud properties should be investigated through in situ measurements and 3-D dynamic models.https://www.atmos-chem-phys.net/18/7313/2018/acp-18-7313-2018.pdf |
| spellingShingle | F. Yang P. Kollias P. Kollias R. A. Shaw A. M. Vogelmann Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation Atmospheric Chemistry and Physics |
| title | Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation |
| title_full | Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation |
| title_fullStr | Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation |
| title_full_unstemmed | Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation |
| title_short | Cloud droplet size distribution broadening during diffusional growth: ripening amplified by deactivation and reactivation |
| title_sort | cloud droplet size distribution broadening during diffusional growth ripening amplified by deactivation and reactivation |
| url | https://www.atmos-chem-phys.net/18/7313/2018/acp-18-7313-2018.pdf |
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