Doppler sodar and radar wind-profiler observations of gravity-wave activity associated with a gravity current

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Monthly Weather Review; (United States)

DOI:https://doi.org/10.1175/1520-0493(1993)121<0444:DSARWP>2.0.CO;2· OSTI ID:6721033

Ralph, F M; Venkateswaran, S V ^[1]; Mazaudier, C ^[2]; Crochet, M ^[3]

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1. Univ. of California, Los Angeles (United States)
2. Centre de Recherches en Physique de l'Environnement Terrestre et Planetaire, Saint-Maur-des-Fosses (France)
3. Universite de Toulon, La Garde (France)

Observations from two Doppler sodars and a radar wind profiler have been used in conjunction with data from a rawinsonde station and a mesoscale surface observation network to conduct a case study of a gravity current entering into an environment containing a nocturnal inversion and an elevated neutral layer. On the basis of synoptic and mesoscale analyses, it is concluded that the gravity current might have originated either as a scale-contracted cold front or as a gust front resulting from thunderstorm outflows observed very near the leading edge of a cold front. Despite this ambiguity, the detailed vertical structure of the gravity current itself is well resolved from the data. Moreover, the vertical velocity measurements provided by the sodars and the radar wind profiler at high time resolution have given unique information about the height structure of gravity waves excited by the gravity current. Although only wave periods, and not phase speeds or wavelengths, are directly measured, it is possible to make reasonable inferences about wave excitation mechanisms and about the influence and control of ambient stratification on wave-field characteristics. Both Kelvin-Helmholtz waves generated in the regions of high wind shear found in association with the gravity current and lee-type waves forced by the gravity current acting as an obstacle to opposing prefrontal flow are identified. It is also found that the propagation speed of the gravity current and the relative depths of the prefrontal inversion and the postfrontal cold air were not favorable for the formation of either internal bores or solitary waves at the time of day at which the gravity current was being observed. 42 refs., 18 figs., 1 tab.

• OSTI ID: 6721033
• Journal Information: Monthly Weather Review; (United States), Vol. 121:2; ISSN 0027-0644
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
EARTH ATMOSPHERE
GRAVITY WAVES
WAVE PROPAGATION
WIND
VELOCITY
EXPERIMENTAL DATA
METEOROLOGY
RADAR
STORMS
TEMPERATURE INVERSIONS
TIME RESOLUTION
DATA
DISASTERS
INFORMATION
MEASURING INSTRUMENTS
NUMERICAL DATA
RANGE FINDERS
RESOLUTION
TIMING PROPERTIES
540110*
580000 - Geosciences