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Numerical simulations of katabatic jumps in coats land, Antartica

Yu, Ye; Cai, Xiaoming; King, John C.; Renfrew, Ian A.. 2005 Numerical simulations of katabatic jumps in coats land, Antartica. Boundary-Layer Meteorology, 114 (2). 413-437. 10.1007/s10546-004-9564-1

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Abstract/Summary

A non-hydrostatic numerical model, the Regional Atmospheric Modeling System (RAMS), has been used to investigate the development of katabatic jumps in Coats Land, Antarctica. In the control run with a 5 m s-1 downslope directed initial wind, a katabatic jump develops near the foot of the idealized slope. The jump is manifested as a rapid deceleration of the downslope flow and a change from supercritical to subcritical flow, in a hydraulic sense, i.e., the Froude number (Fr) of the flow changes from Fr > 1 to Fr> 1. Results from sensitivity experiments show that an increase in the upstream flow rate strengthens the jump, while an increase in the downstream inversion-layer depth results in a retreat of the jump. Hydraulic theory and Bernoulli's theorem have been used to explain the surface pressure change across the jump. It is found that hydraulic theory always underestimates the surface pressure change, while Bernoulli's theorem provides a satisfactory estimation. An analysis of the downs balance for the katabatic jump indicates that the important forces are those related to the pressure gradient, advection and, to a lesser extent, the turbulent momentum divergence. The development of katabatic jumps can be divided into two phases. In phase I, the t gradient force is nearly balanced by advection, while in phase II, the pressure gradient force is counterbalanced by turbulent momentum divergence. The upslope pressure gradient force associated with a pool of cold air over the ice shelf facilitates the formation of the katabatic jump.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1007/s10546-004-9564-1
Programmes: BAS Programmes > Antarctic Science in the Global Context (2000-2005) > Antarctic Climate Processes
ISSN: 0006-8314
Additional Keywords: Winds
NORA Subject Terms: Meteorology and Climatology
Atmospheric Sciences
Date made live: 17 Jan 2008 14:48
URI: http://nora.nerc.ac.uk/id/eprint/2100

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