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Modulation of Tropical Convection-circulation Interaction by Aerosol Indirect Effects in Idealized Simulations of a Global Convection-permitting Model
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  • Chun-Yian Su,
  • Chien-Ming Wu,
  • Wei-Ting Chen,
  • John Peters
Chun-Yian Su
Pennsylvania State University

Corresponding Author:[email protected]

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Chien-Ming Wu
National Taiwan University
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Wei-Ting Chen
National Taiwan University
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John Peters
Penn State
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Observations suggest tropical convection intensifies when aerosol concentrations enhance, but quantitative estimations of this effect remain highly uncertain. Leading theories for explaining the influence of aerosol concentrations on tropical convection are based on the dynamical response of convection to changes in cloud microphysics, neglecting possible changes in the environment. In recent years, global convection-permitting models (GCPM) have been developed to circumvent problems arising from imposing artificial scale separation on physical processes associated with deep convection. Here, we use a GCPM to investigate how enhanced concentrations of aerosols that act as cloud condensate nuclei (CCN) impact tropical convection features by modulating the convection-circulation interaction. Results from a pair of idealized non-rotating radiative-convective equilibrium simulations show that the enhanced CCN concentration leads to weaker large-scale circulation, the closeness of deep convective systems to the moist cluster edges, and more mid-level cloud water at an equilibrium state in which convective self-aggregation occurred. Correspondingly, the enhanced CCN concentration modulates how the diabatic processes that support or oppose convective aggregation maintain the aggregated state at equilibrium. Overall, the enhanced CCN concentration facilitates the development of deep convection in a drier environment but reduces the large-scale instability and the convection intensity. Our results emphasize the importance of allowing atmospheric phenomena to evolve continuously across spatial and temporal scales in simulations when investigating the response of tropical convection to changes in cloud microphysics.
17 Oct 2023Submitted to ESS Open Archive
17 Oct 2023Published in ESS Open Archive