Entrainment of aerosols and their activation in a shallow cumulus cloud studied with a coupled LCM-LES approach

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Autoren

  • F. Hoffmann
  • S. Raasch
  • Y. Noh

Externe Organisationen

  • Yonsei University
Forschungs-netzwerk anzeigen

Details

OriginalspracheEnglisch
Seiten (von - bis)43-57
Seitenumfang15
FachzeitschriftAtmospheric research
Jahrgang156
Frühes Online-Datum26 Dez. 2014
PublikationsstatusVeröffentlicht - 1 Apr. 2015

Abstract

This study investigates how entrainment affects the activation of aerosols in a shallow cumulus cloud using large-eddy simulations (LES) with an embedded Lagrangian cloud model (LCM) in which aerosols and droplets are explicitly treated as Lagrangian particles. The activation process is analyzed for aerosols entrained (i) by the central updraft at cloud base and (ii) by turbulent mixing above cloud base (lateral entrainment). Cloud base aerosols and laterally entrained aerosols contribute to all activated aerosols inside the cloud by fractions of 70% and 30%, respectively. Laterally entrained particles dominate the activation above cloud base (secondary activation), to which cloud base aerosols contribute about one third. As assumed in many parameterizations, the activation of cloud base aerosols is limited by the maximum saturation. However, the activation of laterally entrained aerosols is determined by the degree of turbulence, limiting the time available for activation and restricting the activation to intermediate sized aerosols, which demand the shortest time for activation. As the environmental aerosol concentration increases, activation of laterally entrained aerosols becomes more important.

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Entrainment of aerosols and their activation in a shallow cumulus cloud studied with a coupled LCM-LES approach. / Hoffmann, F.; Raasch, S.; Noh, Y.
in: Atmospheric research, Jahrgang 156, 01.04.2015, S. 43-57.

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Hoffmann F, Raasch S, Noh Y. Entrainment of aerosols and their activation in a shallow cumulus cloud studied with a coupled LCM-LES approach. Atmospheric research. 2015 Apr 1;156:43-57. Epub 2014 Dez 26. doi: 10.1016/j.atmosres.2014.12.008
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abstract = "This study investigates how entrainment affects the activation of aerosols in a shallow cumulus cloud using large-eddy simulations (LES) with an embedded Lagrangian cloud model (LCM) in which aerosols and droplets are explicitly treated as Lagrangian particles. The activation process is analyzed for aerosols entrained (i) by the central updraft at cloud base and (ii) by turbulent mixing above cloud base (lateral entrainment). Cloud base aerosols and laterally entrained aerosols contribute to all activated aerosols inside the cloud by fractions of 70% and 30%, respectively. Laterally entrained particles dominate the activation above cloud base (secondary activation), to which cloud base aerosols contribute about one third. As assumed in many parameterizations, the activation of cloud base aerosols is limited by the maximum saturation. However, the activation of laterally entrained aerosols is determined by the degree of turbulence, limiting the time available for activation and restricting the activation to intermediate sized aerosols, which demand the shortest time for activation. As the environmental aerosol concentration increases, activation of laterally entrained aerosols becomes more important.",
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