Initiation of a Solitary Wave Family in the Demise of a Nocturnal Thunderstorm Density Current

Fulton, Richard; Zrnić, Dúsan S.; Doviak, Richard J.

doi:10.1175/1520-0469(1990)047<0319:ioaswf>2.0.co;2

Cited by 60 publications

(51 citation statements)

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“…Perhaps the most recognizable is the Morning Glory of the Gulf of Carpentaria in northern Australia, which was first identified as an internal undular bore initiated by the interaction of a sea breeze and a nocturnal inversion by Clarke et al (1981). Many bores have been identified in the central United States (Doviak and Ge 1984;Haase and Smith 1984;Carbone et al 1990;Fulton et al 1990;Demoz et al 2005), Florida (Wakimoto and Kingsmill 1995;Kingsmill and Crook 2003), and other regions of the world. Prior to the 2004 NAME, there has been no evidence of bores being observed in the NAM domain.…”

Section: Introductionsupporting

confidence: 79%

“…First, circulations produced by bores (and other similar phenomenon) may be capable of directly triggering convection, as maximum vertical velocities have been observed up to 15 m s Ϫ1 (Shreffler and Binkowski 1981;Carbone et al 1990;Fulton et al 1990;Karyampudi et al 1995). The convection that is triggered by bores can range from roll clouds (Clarke et al 1981) and light showers to squall lines with tornadic storms (Karyampudi et al 1995), although the latter do not occur in the NAM region.…”

Section: Introductionmentioning

confidence: 67%

“…The wavelength fits within the range of observations from previous studies. The greater distance between the first undulations compared to the succeeding undulations has also been observed in studies of bores and solitary waves (Fulton et al 1990) and is attributed to the larger amplitude of the initial undulation (or wave), hence, a greater propagation speed of the first undulation and increased separation between the first two wave crests. A second layer of enhanced SNR observed at 1 km at 0400 UTC was elevated approximately 800 m by the passage of the bore at 0435 UTC.…”

Section: B 915-mhz Doppler Clear-air Wind Profilermentioning

confidence: 99%

“…Several theories have been proposed as to the possible external force required for the generation of bores. Cool air behind colliding gravity currents (Clarke et al 1981;Clarke 1984;Noonan and Smith 1987;Wakimoto and Kingsmill 1995;Kingsmill and Crook 2003), thunderstorm outflows (Fulton et al 1990;Koch et al 1991;Mahapatra et al 1991;Locatelli et al 1998;Koch et al 2005;Knupp 2006), and mesoscale fronts (Karyampudi et al 1995;Smith et al 1995;Koch and Clark 1999;Demoz et al 2005) interacting with an existing stable layer may trigger bore disturbances. However, complications to these ideas arise in the real atmosphere because of complex stratification, vertical shear, elevated FIG.…”

Section: Introductionmentioning

confidence: 99%

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An Observational and Modeling Study of an Atmospheric Internal Bore during NAME 2004

Martin

Johnson

2008

Monthly Weather Review

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Observations from the 2004 North American Monsoon Experiment (NAME) have been used to identify an atmospheric internal bore that occurred over the Gulf of California (GoC) on 31 July 2004. This bore disturbance was identified at Bahia Kino along the northwest coast of Mexico during the late evening of 31 July. It was hypothesized to have originated from the interaction of a gravity current from a large mesoscale convective system (MCS), which formed along the western slopes of the Sierra Madre Occidental during the afternoon, and a surface stable layer that developed from a sea-breeze circulation. It is suggested that the bore's energy was trapped at low levels by an elevated stable layer. The vertical structure and undular nature of the bore was initially identified from 915-MHz wind profiler data at Bahia Kino. Results show a series of waves along the bore's leading edge and turbulent mixing of air from above the stable layer to the surface on the downstream face of the leading undulation. The speed of the bore calculated from satellite imagery and surface observations (approximately 16.8 m s Ϫ1) compared favorably with the speed of a bore from hydraulic theory when a reliable estimate of the bore depth was used.A real-data simulation of the event was performed using the Weather Research and Forecasting model (WRF). Results show the model captured both the formation mechanism and structure of the bore, but it was produced too far south compared to observations, as the MCS also developed too far south. Model results indicated that while evidence of a trapping mechanism due to the stability of the atmosphere was present in the simulation, the conditions for trapping were modified by the passage of the bore allowing vertical propagation of wave energy. The bore led to increased moisture in the lowest levels of the atmosphere across the GoC, providing evidence of the possible importance of these features as moisture transport mechanisms in this region.

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Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 67%

Section: B 915-mhz Doppler Clear-air Wind Profilermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Observational and Modeling Study of an Atmospheric Internal Bore during NAME 2004

Martin

Johnson

2008

Monthly Weather Review

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“…Such phenomena have often been observed in association with thunderstorm outflow and sea-breeze fronts (e.g. Fulton et al, 1990 and references therein). The conditions for the formation of these nonlinear waves has been studied by Haase and Smith (1989) with a numerical model.…”

Section: The Solitary Wave and Its Ducting Mechanismmentioning

confidence: 98%

An observational study of a shallow gravity current triggered by katabatic flow

Adachi

Clark²,

Hartten³

et al. 2004

Ann. Geophys.

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Abstract.Observations from a wind profiler and a meteorological tower are utilized to study the evolution of a gravity current that passed over the Meteorological Research Institute's (MRI) field site in Tsukuba, Japan. The gravity current was created by katabatic flow originating on the mountainous slopes west of the field site. The passage of the shallow current was marked by a pronounced pressure disturbance and was accompanied by vertical circulations seen in the tower and profiler data. Direct vertical-beam measurements are difficult, especially at low heights during highgradient events like density currents. In this study vertical velocities from the profiler are derived from the four oblique beams by use of the Minimizing the Variance of the Differences (MVD) method. The vertical velocities derived from the MVD method agree well with in situ vertical velocities measured by a sonic anemometer on the tower.The gravity current is analyzed with surface observations, the wind profiler/RASS and tower-mounted instruments. Observations from the profiler/RASS and the tower-mounted instruments illustrate the structure of the gravity current in both wind and temperature fields. The profiler data reveal that there were three regions of waves in the vertical velocity field: lee-type waves, a solitary wave and Kelvin-Helmholtz waves. The lee-type waves in the head region of the gravity current seem to have been generated by the gravity current acting as an obstacle to prefrontal flow. The solitary wave was formed from the elevated head of the gravity current that separated from the feeder flow. Profiler vertical-motion observations resolve this wave and enable us to classify it as a Benjamin-Davis-Ono (BDO) type solitary wave. The ducting mechanism that enabled the solitary wave to propagate is also revealed from the wind profiler/RASS measurements. The combination of high-resolution instruments at the MRI site allow us to develop a uniquely detailed picture of a shallow gravity current structure.

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Dust emission and transport mechanisms in the central Sahara: Fennec ground‐based observations from Bordj Badji Mokhtar, June 2011

2013

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[1] A detailed analysis of the first ever high-resolution ground-based dust observations in the remote central Sahara is presented from observations at Bordj Badji Mokhtar (BBM), taken during the Fennec project in June 2011. Detailed case studies are presented for three dust-producing mechanisms (cold pool outflows, low-level jets (LLJs), and dry convective plumes). The results confirm the importance of cold pools in dust emission and transport in the region. Forty-five percent of the dust over BBM is generated by local emission in cold pool outflows. Twenty-seven percent of the dust is advected rather than locally emitted dust; on three occasions, it is advected over 500 km to BBM by cold pool outflows. Dust that has been in long-range transport to the area within such cold pool outflows is found to carry larger particles and be responsible for higher dust loadings than fresh uplift. LLJs are of tertiary importance in the partitioning, responsible for 14% dust over BBM. Dry convective plumes are identifiable in the data but produce much less significant quantities of dust, approximately 2% of the June total. The cube of wind speed has a stronger correlation with dust emission than wind speed. The correlation is strongest (at 95% confidence) for LLJ-induced emission (0.88), followed by locally emitting cold pools (0.78).Citation: Allen, C. J. T., R. Washington, and S. Engelstaedter (2013), Dust emission and transport mechanisms in the central Sahara: Fennec ground-based observations from

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Initiation of a Solitary Wave Family in the Demise of a Nocturnal Thunderstorm Density Current

Cited by 60 publications

References 0 publications

An Observational and Modeling Study of an Atmospheric Internal Bore during NAME 2004

An Observational and Modeling Study of an Atmospheric Internal Bore during NAME 2004

An observational study of a shallow gravity current triggered by katabatic flow

Dust emission and transport mechanisms in the central Sahara: Fennec ground‐based observations from Bordj Badji Mokhtar, June 2011

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