Wave ducting in a stratified shear flow over a two-dimensional mountain. Part II: Implications for the development of high-drag states for severe downslope windstorms

From: Journal of the Atmospheric Sciences | Date: February 1, 1999| Author: | Copyright information

ABSTRACT

In this study, it is found that the discrepancies among earlier studies of severe downslope windstorms are caused by the use of the critical level height (z^sub c^) instead of the low-level uniform flow-layer depth (z^sub 1^), as an indicator to determine the optimal conditions for the occurrence of high-drag states. It is determined that once the wave breaking occurs, it induces a critical level and establishes a flow configuration favorable for wave ducting in the lower uniform wind layer, which determines the phase of reflected waves.

Flow regimes of high- and low-drag states ...

Read all of this article with a FREE trial to HighBeam Research

Related newspaper, magazine, and trade journal articles from HighBeam Research

(Including press releases, facts, information, and biographies)

Critical levels
; ...according to informed sources, the critical level would be 95.6 metres. At the Langat...level is now at 218 metres, and the critical level is said to be 204.2 metres. Over at...level now is at 94 metres, and the critical level is 84 metres. And at Batu, the water...
Transient, linear dynamics of a stably stratified shear flow with thermal forcing and a critical level
; ...thermal forcing in the presence of a critical level is investigated analytically using...forcing is located below or across a critical level. The target solution is for the finite-dep...gravity waves are attenuated across the critical level. In response to the line-type pulse...
Delay in rice-planting season seen.(Metro & National News)
; ...Angat Dam may still be way below its critical level by that time, the National Water Resources...meters, 15 meters below its 180-meter critical level. During the June planting season last...12), the water reservoir reached its critical level but the NWRB extended the water ...
The propagation of a gravity-inertia wave in a positively sheared flow
; ...over a stationary boundary above the critical level, its vertical propagation will depend...we considered the cases in which a critical level exists in the flow (mean flow decreasing...situation of a gravity wave encountering a critical level, but with this important difference...
A Study of Two-Dimensional Dry Convective Plume Modes with Variable Critical Level Height
; ...investigates the impact of wind speed and critical level height on dry convection above a prescribed...unstable shear flow centered at the critical level. The third mode, termed the intense...upper-level outflow. The presence of a critical level is shown to be crucial to the ...
`Residents may have to evacuate'
; ...the moment the air quality reaches critical level of 50ppm (part per million). State...level of pollution. "If it reaches the critical level, then residents staying near the factory...Although today's reading was below the critical level, Mohd Mokhtar had directed the DOE...
Shortage 'critical'
; ...Sandra Lyall, human resources director for Unisys New Zealand, says the shortage has has reached a critical level. "It has reached a critical level. In the past, talent management and retention programmes have been a perk for employees. Effective...
Windstorms along the western side of the Washington Cascade Mountains. Part II: Characteristics of past events and three-dimensional idealized simulations
; ...the western Washington Cascades to critical-level height, cross-barrier pressure gradient...Although many windstorm cases had a critical level in the middle troposphere, several...gt;13 m s 1) when an environmental critical level exists below 400 mb. However, even...
WALES ON HIGHEST STATE OF ALERT.(News)
; ...following the terror bombings in London. Wales is now on Critical Level 1 alert after four bombs ripped through the London Underground...changed,' he said. 'The threat level has been raised to Critical Level 1, whereas last Wednesday it was severe. 'There are higher...
Families in fear of dam collapse; CAPITAL WORST HIT BY DELUGE AS A MONTH'S RAIN FALLS IN 36 HOURS.(News)
; ...floodrisk reservoir were urged to evacuate as it reached a critical level yesterday. But last night, only six of the households had...raised the water level in the Maich fisheries reservoir to a critical level. We and council staff have been working round the clock...