Vertical Motions in Orographic Cloud Systems over the Payette River Basin. Part II: Fixed and Transient Updrafts and Their Relationship to Forcing

Troy J. Zaremba, Kaylee Heimes, Robert M. Rauber, Bart Geerts, Jeffrey R. French, Coltin Grasmick, Sarah A. Tessendorf, Lulin Xue, Katja Friedrich, Roy M. Rasmussen, Melvin L. Kunkel, Derek R. Blestrud

Research output: Contribution to journalArticlepeer-review


Updrafts in wintertime cloud systems over mountainous regions can be described as fixed, mechanically driven by the terrain under a given ambient wind and stability profile (i.e., vertically propagating gravity waves tied to flow over topography), and transient, associated primarily with vertical wind shear and conditional instability within passing weather systems. This analysis quantifies the magnitude of fixed and transient updraft structures over the Payette River basin sampled during the Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE). Vertical motions were retrieved from Wyoming Cloud Radar measurements of radial velocity using the algorithm presented in Part I. Transient circulations were removed, and fixed orographic circulations were quantified by averaging vertical circulations along repeated cross sections over the same terrain during the campaign. Fixed orographic vertical circulations had magnitudes of 0.3–0.5 m s21. These fixed vertical circulations were composed of a background circulation in which transient circulations were embedded. Transient vertical circulations are shown to be associated with transient wave motions, cloud-top generating cells, convection, and turbulence. Representative transient vertical circulations are illustrated, and data from rawin-sondes over the Payette River basin are used to infer the relationship of the vertical circulations to shear and instability. Maximum updrafts are shown to exceed 5 m s21 within Kelvin–Helmholtz waves, 4 m s21 associated with transient gravity waves, 3 m s21 in generating cells, 6 m s21 in elevated convection, 4 m s21 in surface-based deep convection, 5 m s21 in boundary layer turbulence, and 9 m s21 in shear-induced turbulence.

Original languageEnglish (US)
Pages (from-to)1727-1745
Number of pages19
JournalJournal of Applied Meteorology and Climatology
Issue number11
StatePublished - Oct 2022


  • Orographic effects
  • Updrafts/downdrafts
  • Vertical motion

ASJC Scopus subject areas

  • Atmospheric Science


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