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Spatial organisation affects the pathway to precipitation in simulated trade-wind convection
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  • Jule Radtke,
  • Raphaela Vogel,
  • Felix Ament,
  • Ann Kristin Naumann
Jule Radtke
Meteorological Institute, Center for Earth System Research and Sustainability, Universit├Ąt Hamburg

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Raphaela Vogel
Meteorological Institute, Center for Earth System Research and Sustainability, Universit├Ąt Hamburg
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Felix Ament
University Hamburg
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Ann Kristin Naumann
Max Planck Institute for Meteorology
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Abstract

We investigate whether and how spatial organisation affects the pathway to precipitation in large-domain hectometer simulations of the North Atlantic trades. We decompose the development of surface precipitation (P) in warm shallow trade cumulus into a formation phase, where cloud condensate is converted into rain, and a sedimentation phase, where rain falls towards the ground while some of it evaporates. With strengthened organisation, rain forms in weaker updrafts from smaller cloud droplets so that cloud condensate is less efficiently converted into rain. At the same time, organisation creates a locally moister environment and modulates the microphysical conversion processes that determine the raindrops' size. This reduces evaporation and more of the formed rain reaches the ground. Organisation thus affects how the two phases contribute to P, but only weakly affects the total precipitation efficiency. We conclude that the pathway to precipitation differs with organisation and suggest that organisation buffers rain development.