Preprints
https://doi.org/10.5194/acp-2020-875
https://doi.org/10.5194/acp-2020-875

  18 Sep 2020

18 Sep 2020

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Convective self–aggregation in a mean flow

Hyunju Jung1,a, Ann Kristin Naumann1, and Bjorn Stevens1 Hyunju Jung et al.
  • 1Max Plank Institute for Meteorology, Hamburg, Germany
  • acurrently at: Institute of Meteorology and Climate Research (IMK–TRO), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany

Abstract. Convective self-aggregation is an atmospheric phenomenon found in numerical simulations in a radiative convective equilibrium framework of which configuration captures the main characteristics of the real-world convection in the deep tropics. As tropical deep convection is typically embedded in a large-scale flow, we impose a background mean wind flow on convection-permitting simulations through the surface flux calculation. The simulations show that with imposing mean flow, the organized convective system propagates in the direction of the flow but slows down compared to what pure advection would suggest, and eventually becomes stationary relative to the surface after 15 simulation days. The termination of the propagation arises from momentum flux, which acts as a drag on the near-surface horizontal wind. In contrast, the thermodynamic response through the wind-induced surface heat exchange feedback is a relatively small effect, which slightly retards (by about 15 %) the convection relative to the mean wind.

Hyunju Jung et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Hyunju Jung et al.

Hyunju Jung et al.

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Short summary
We aim to analyze the behavior of organized convection in a large-scale flow by imposing a mean flow to an idealized simulation. In the mean flow organized convection initially propagates slower than the mean wind speed and becomes stationary. Surface fluxes response to the surface wind asymmetry as a result of the mean flow. While the role of the surface enthalpy flux is minor, the surface momentum flux act as a drag on the surface wind and annihilate the asymmetries, causing the stationarity.
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