Structure and Life Cycle of Microburst Outflows Observed in Colorado

Hjelmfelt, Mark R.

doi:10.1175/1520-0450(1988)027<0900:salcom>2.0.co;2

Cited by 402 publications

(188 citation statements)

References 18 publications

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“…Selvam and Holmes (1992) were the first to use a numerical simulation of a wall jet to study the wind flow over objects. Experimental and numerical results attained via impinging jet model showed good agreements with full-scale data (e.g., Hjelmfelt, 1988;Caracena et al, 1989;Selvam and Holmes, 1992). Later, by utilization of impinging jet model, numerous physical and numerical simulation were conducted to achieve a comprehensive understanding of the downbursts or its effects (e.g., Wood et Li et al, 2012).…”

Section: Introductionsupporting

confidence: 52%

Dynamic Response of Flat Roofs Subjected to Non-Stationary Moving Microbursts

Chen¹,

Guo-guang²,

Sun³

2013

Engineering Applications of Computational Fluid Mechanics

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This paper deals with the dynamic response of a flat roof which is subjected to a moving microburst. Taking the fluid-structure interaction into account, a methodology for the numerical simulation of the time histories of wind pressures on the roof is proposed by retrofitting the usage of deterministic-stochastic hybrid model. Whereby, the dynamic response of the roof could be computed. Gust-front factor, which is defined as the ratio of the maximum response caused by downburst to that caused by atmospheric boundary layer wind, is employed herein for dynamical analysis. The results indicate that the ratio of jet velocity to translating speed of the microburst has a significant influence on the peak value of the wind pressure coefficient. It is found that the gust-front factor decreases with the increase of jet velocity of the microburst, and increases with the first natural frequency of the roof.

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Section: Introductionsupporting

confidence: 52%

Dynamic Response of Flat Roofs Subjected to Non-Stationary Moving Microbursts

Chen¹,

Guo-guang²,

Sun³

2013

Engineering Applications of Computational Fluid Mechanics

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“…This second surge in the wind field, despite not characterizing a true additional burst, appears to represent a manifestation of a pulsation in the microburst behaviour, which has been detected in radar velocity fields (see Fig. 8 of Hjelmfelt, 1988) and studied in Proctor (1993). Further studies are necessary to better understand the basic dynamics behind such behaviour.…”

Section: Qualitative Comparisonsmentioning

confidence: 58%

“…The term "wall jet" is usually employed in fluid dynamics to illustrate the typology of shallow flow that occurs when a cold fluid impinges a flat surface at high speed (Hjelmfelt, 1988).…”

Section: Qualitative Comparisonsmentioning

confidence: 99%

Large-Eddy Simulation of a microburst

et al. 2011

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Abstract. The three-dimensional structure and evolution of an isolated and stationary microburst are simulated using a time-dependent, high resolution Large-Eddy-Simulation (LES) model. The microburst is initiated by specifying a simplified cooling source at the top of the domain around 2 km a.g.l. that leads to a strong downdraft. Surface winds of the order of 30 m s −1 were obtained over a region of 500 m radius around the central point of the impinging downdraft, with the simulated microburst lasting for a few minutes. These characteristic length and time scales are consistent with results obtained from numerical simulations of microbursts using cloud-resolving models. The simulated flow replicated some of the principal features of microbursts observed by Doppler radars: in particular, the horizontal spread of strong surface winds and a ring vortex at the leading edge of the cold outflow. In addition to the primary surface outflow, the simulation also generated a secondary surge of strong winds that appears to represent a pulsation in the microburst evolution.These results highlight the capability of LES to reproduce complex phenomena like microbursts, indicating the potential usage of LES models to represent atmospheric phenomena of time and space scales between the convective scale and the microscale. These include short-lived convectivelygenerated damaging winds.

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“…Fujita (1986) investigated downbursts / microbursts and explained ground-damage patterns. Wakimoto (1982), Wilson et al (1984) and Hjelmfelt (1988) presented the life cycle of a thunderstorm outflow and a microburst based on Doppler radar observations. Schematic cross section through a gust front was showed by Charba (1974).…”

Section: Introductionmentioning

confidence: 99%

Observation of downburst event in Gunma prefecture on August 11, 2013 using a surface dense observation network

Norose

Kobayashi

Kure

et al. 2015

JAE

141

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Abstract. On the evening of August 11, 2013, a severe thunderstorm passed over Takasaki and Maebashi City in Gunma Prefecture, Japan, causing extensive wind damage due to gusts. Changes in surface weather elements associated with the gusts were recorded by the dense network of surface meteorological observation stations ("POTEKA"), which the compact weather stations were set up at primary schools and convenience stores. We examined the development and propagation of a gust front and a downburst by analyzing the characteristics of the pressure field recorded by the POTEKA network. Temporal changes in surface pressure observed in the damaged area were characterized by two episodes of marked increases in atmospheric pressure. The propagation of two marked increases in pressure (0.5 to 1.5 hPa for peak 1, 1.5 to 2.5 hPa for peak 2) was revealed and a cold-air depth of 200 to 600 m and an average propagation speed of 10 ms -1 . Based on the time of damage and meteorological observations, the second increase in pressure coincided with the occurrence of both damage and a gust. On the basis of the POTEKA data, the cause of the damage was attributed to the downburst.

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Structure and Life Cycle of Microburst Outflows Observed in Colorado

Cited by 402 publications

References 18 publications

Dynamic Response of Flat Roofs Subjected to Non-Stationary Moving Microbursts

Dynamic Response of Flat Roofs Subjected to Non-Stationary Moving Microbursts

Large-Eddy Simulation of a microburst

Observation of downburst event in Gunma prefecture on August 11, 2013 using a surface dense observation network

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