Webbläsaren som du använder stöds inte av denna webbplats. Alla versioner av Internet Explorer stöds inte längre, av oss eller Microsoft (läs mer här: * https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Var god och använd en modern webbläsare för att ta del av denna webbplats, som t.ex. nyaste versioner av Edge, Chrome, Firefox eller Safari osv.

Default user image.

Vaughan Phillips

Universitetslektor

Default user image.

A Theory for the Balance between Warm Rain and Ice Crystal Processes of Precipitation in Mixed-Phase Clouds

Författare

  • Vaughan T.J. Phillips

Summary, in English

Mixed-phase clouds contain both supercooled cloud liquid and ice crystals. In principle, precipitation may be initiated either by the liquid phase or by the ice phase. Ice crystals may grow by vapor diffusion to become snow ("ice crystal process"), forming "cold"precipitation. Equally, cloud droplets, when large enough, coalesce to form "warm"precipitation by the "warm rain process."Warm rain could be supercooled and freeze as "warm"graupel. In the present paper, a new simplified theoretical analysis is provided to examine the microphysical system consisting of three species of hydrometeor, namely, cloud liquid, "cold ice"(crystals, snow), and "warm rain"(frozen or supercooled). This is obtained by nondimensionalizing and simplifying the evolution equations for the mass of each species. Analytical formulas are given for equilibria. Feedback analysis shows that the sign of the feedback is linked to the abundance of precipitation, with a neutral surface in the 3D phase space. The system's precipitation amount explodes while in the initial unstable regime, crossing the neutral surface and approaching the equilibrium point that is a stable attractor. Positive and negative feedbacks are elucidated. In a standard case, the cold ice mass is about 1000 times larger than the warm rain mass. To illustrate the physical behavior of the theory, sensitivity tests are performed with respect to environmental conditions (e.g., aerosol, updraft speed) and microphysical parameters (e.g., riming and sedimentation rates for cold ice). Cold ice prevails, especially in fast ascent, due to its low bulk density, favoring slow sedimentation and a wide cross-sectional area for riming. SIGNIFICANCE STATEMENT: The theory elucidates how the ice phase can prevail in the precipitation from any mixed-phase clouds with supercooled cloud liquid and crystals. The ice phase radically suppresses cloud liquid by riming when active and "wins"the competition against coalescence. This prevalence of ice is shown to arise from the low bulk density of snow. The cloud is viewed as a system of negative and positive feedbacks that prevail in realms of stability and instability in a 3D phase space.

Avdelning/ar

  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • eSSENCE: The e-Science Collaboration
  • Institutionen för naturgeografi och ekosystemvetenskap
  • MERGE: ModElling the Regional and Global Earth system

Publiceringsår

2024

Språk

Engelska

Sidor

317-339

Publikation/Tidskrift/Serie

Journal of the Atmospheric Sciences

Volym

81

Issue

2

Dokumenttyp

Artikel i tidskrift

Förlag

Amer Meteorological Soc

Ämne

  • Meteorology and Atmospheric Sciences

Nyckelord

  • Cloud microphysics
  • Ice loss/growth
  • Mixed precipitation

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0022-4928