Dynamics of cloud-top generating cells in winter cyclones. Part II: Radiative and instability forcing

Jason M. Keeler, Brian F. Jewett, Robert M. Rauber, Greg M. McFarquhar, Roy M. Rasmussen, Lulin Xue, Changhai Liu, Gregory Thompson

Research output: Contribution to journalArticle

Abstract

Recent field observations suggest that cloud-top precipitation generating cells (GCs) are ubiquitous in the warm-frontal and comma-head regions of midlatitude winter cyclones. The presence of fallstreaks emanating from the GCs and their persistence either to the surface or until merging into precipitation bands suggests that GCs are a critical component of the precipitation process in these cyclones. This paper is the second part of a three-part series that investigates the dynamics of GCs through very-high-resolution idealized Weather Research and Forecasting (WRF) Model simulations. This paper assesses the role of cloud-top instability paired with nighttime, daytime, or no radiative forcing on the development and maintenance (or lack) of GCs. Under initially unstable conditions at cloud top, GCs develop regardless of radiative forcing but only persist clearly with radiative forcing. Cloud-top destabilization due to longwave cooling leads to development of GCs even under initially neutral and stable conditions, providing a physical explanation for the observed ubiquity of GCs atop winter cyclones. GCs do not develop in initially stable simulations with no radiation. Decreased range in vertical velocity spectra under daytime radiative forcing is consistent with offset of the destabilizing influence of longwave cooling by shortwave heating.

Original languageEnglish (US)
Pages (from-to)1529-1553
Number of pages25
JournalJournal of the Atmospheric Sciences
Volume73
Issue number4
DOIs
StatePublished - Apr 1 2016

Keywords

  • Atm/Ocean structure/ Phenomena
  • Circulation/ Dynamics
  • Cloud radiative effects
  • Cloud resolving models
  • Convective-scale processes
  • Large eddy simulations
  • Models and modeling
  • Physical meteorology and climatology
  • Precipitation
  • Snow

ASJC Scopus subject areas

  • Atmospheric Science

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    Keeler, J. M., Jewett, B. F., Rauber, R. M., McFarquhar, G. M., Rasmussen, R. M., Xue, L., Liu, C., & Thompson, G. (2016). Dynamics of cloud-top generating cells in winter cyclones. Part II: Radiative and instability forcing. Journal of the Atmospheric Sciences, 73(4), 1529-1553. https://doi.org/10.1175/JAS-D-15-0127.1