Atmospheric rotors and severe turbulence in a long deep valley

Author(s)
Stefano Serafin, Lukas Strauss, Vanda Grubisic
Abstract

The conceptual model of an atmospheric rotor is reexamined in the context of a valley, using data from the Terrain-Induced Rotor Experiment (T-REX) conducted in 2006 in the southern Sierra Nevada and Owens Valley, California. All T-REX cases with strong mountain-wave activity have been investigated, and four of them (IOPs 1, 4, 6, and 13) are presented in detail. Their analysis reveals a rich variety of rotorlike turbulent flow structures that may form in the valley during periods of strong cross-mountain winds. Typical flow scenarios in the valley include elevated turbulence zones, downslope flow separation at a valley inversion, turbulent interaction of in-valley westerlies and along-valley flows, and highly transient mountain waves and rotors. The scenarios can be related to different stages of the passage of midlatitude frontal systems across the region. The observations from Owens Valley show that the elements of the classic rotor concept are modulated and, at times, almost completely offset by dynamically and thermally driven processes in the valley. Strong lee-side pressure perturbations induced by large-amplitude waves, commonly regarded as the prerequisite for flow separation, are found to be only one of the factors controlling rotor formation and severe turbulence generation in the valley. Buoyancy perturbations in the thermally layered valley atmosphere appear to play a role in many of the observed cases. Based on observational evidence from T-REX, extensions to the classic rotor concept, appropriate for a long deep valley, are proposed.

Organisation(s)
Department of Meteorology and Geophysics
External organisation(s)
National Center for Atmospheric Research (NCAR)
Journal
Journal of the Atmospheric Sciences
Volume
73
Pages
1481-1506
No. of pages
26
ISSN
0022-4928
DOI
https://doi.org/10.1175/JAS-D-15-0192.1
Publication date
04-2016
Peer reviewed
Yes
Austrian Fields of Science 2012
105206 Meteorology
Keywords
ASJC Scopus subject areas
Atmospheric Science
Portal url
https://ucrisportal.univie.ac.at/en/publications/atmospheric-rotors-and-severe-turbulence-in-a-long-deep-valley(08f6ee6d-3ba0-4a2a-953d-c5aa66c192e8).html