High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus
Abstract A new Aitken mode aerosol microphysics scheme is developed for a large eddy simulation model in order to better investigate cloud‐aerosol interactions in the marine boundary layer and to study the Aitken buffering hypothesis of McCoy et al. (2021), https://doi.org/10.1029/2020jd033529. This...
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American Geophysical Union (AGU)
2022-06-01
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| Series: | Journal of Advances in Modeling Earth Systems |
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| Online Access: | https://doi.org/10.1029/2021MS002930 |
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| author | Matthew C. Wyant Christopher S. Bretherton Robert Wood Peter N. Blossey Isabel L. McCoy |
| author_facet | Matthew C. Wyant Christopher S. Bretherton Robert Wood Peter N. Blossey Isabel L. McCoy |
| author_sort | Matthew C. Wyant |
| collection | DOAJ |
| description | Abstract A new Aitken mode aerosol microphysics scheme is developed for a large eddy simulation model in order to better investigate cloud‐aerosol interactions in the marine boundary layer and to study the Aitken buffering hypothesis of McCoy et al. (2021), https://doi.org/10.1029/2020jd033529. This scheme extends the single‐mode two‐moment prognostic aerosol scheme of Berner et al. (2013), https://doi.org/10.5194/acp-13-12549-2013. Seven prognostic variables represent accumulation and Aitken log‐normal aerosol modes in air and droplets as well as 3 gas species. Scavenging of interstitial and other unactivated aerosol by cloud and rain drops are treated using the scheme described in Berner et al. (2013), https://doi.org/10.5194/acp-13-12549-2013. The scheme includes coagulation of unactivated aerosol and a simple chemistry model with gas phase H2SO4, SO2, and DMS as prognostic variables to capture basic influences of sulfur chemistry on the model aerosols. Nucleation of H2SO4 aerosol particles from gas‐phase H2SO4 is neglected. A deep, precipitating stratocumulus case (VAMOS Ocean Cloud Atmosphere Land Study RF06) is used to test the new scheme. The presence of the Aitken mode aerosol increases the cloud droplet concentration through activation of the larger Aitken particles and delays the creation of an ultraclean, strongly precipitating cumulus state. Scavenging of unactivated accumulation and Aitken particles by cloud and precipitation droplets accelerates the collapse. Increasing either the above‐inversion Aitken concentration or the surface Aitken flux increases the Aitken population in the boundary layer and prevents the transition to an ultraclean state. |
| format | Article |
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| institution | Kabale University |
| issn | 1942-2466 |
| language | English |
| publishDate | 2022-06-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj-art-afe0bc237ffe47d59f7fb38df64c088f2025-08-20T03:53:17ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662022-06-01146n/an/a10.1029/2021MS002930High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating StratocumulusMatthew C. Wyant0Christopher S. Bretherton1Robert Wood2Peter N. Blossey3Isabel L. McCoy4University of Washington Seattle WA USAUniversity of Washington Seattle WA USAUniversity of Washington Seattle WA USAUniversity of Washington Seattle WA USARosenstiel School of Marine and Atmospheric Science University of Miami Miami FL USAAbstract A new Aitken mode aerosol microphysics scheme is developed for a large eddy simulation model in order to better investigate cloud‐aerosol interactions in the marine boundary layer and to study the Aitken buffering hypothesis of McCoy et al. (2021), https://doi.org/10.1029/2020jd033529. This scheme extends the single‐mode two‐moment prognostic aerosol scheme of Berner et al. (2013), https://doi.org/10.5194/acp-13-12549-2013. Seven prognostic variables represent accumulation and Aitken log‐normal aerosol modes in air and droplets as well as 3 gas species. Scavenging of interstitial and other unactivated aerosol by cloud and rain drops are treated using the scheme described in Berner et al. (2013), https://doi.org/10.5194/acp-13-12549-2013. The scheme includes coagulation of unactivated aerosol and a simple chemistry model with gas phase H2SO4, SO2, and DMS as prognostic variables to capture basic influences of sulfur chemistry on the model aerosols. Nucleation of H2SO4 aerosol particles from gas‐phase H2SO4 is neglected. A deep, precipitating stratocumulus case (VAMOS Ocean Cloud Atmosphere Land Study RF06) is used to test the new scheme. The presence of the Aitken mode aerosol increases the cloud droplet concentration through activation of the larger Aitken particles and delays the creation of an ultraclean, strongly precipitating cumulus state. Scavenging of unactivated accumulation and Aitken particles by cloud and precipitation droplets accelerates the collapse. Increasing either the above‐inversion Aitken concentration or the surface Aitken flux increases the Aitken population in the boundary layer and prevents the transition to an ultraclean state.https://doi.org/10.1029/2021MS002930Aitken‐mode aerosolstratocumuluslarge‐eddy simulationmarine boundary layer |
| spellingShingle | Matthew C. Wyant Christopher S. Bretherton Robert Wood Peter N. Blossey Isabel L. McCoy High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus Journal of Advances in Modeling Earth Systems Aitken‐mode aerosol stratocumulus large‐eddy simulation marine boundary layer |
| title | High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus |
| title_full | High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus |
| title_fullStr | High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus |
| title_full_unstemmed | High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus |
| title_short | High Free‐Tropospheric Aitken‐Mode Aerosol Concentrations Buffer Cloud Droplet Concentrations in Large‐Eddy Simulations of Precipitating Stratocumulus |
| title_sort | high free tropospheric aitken mode aerosol concentrations buffer cloud droplet concentrations in large eddy simulations of precipitating stratocumulus |
| topic | Aitken‐mode aerosol stratocumulus large‐eddy simulation marine boundary layer |
| url | https://doi.org/10.1029/2021MS002930 |
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