Gust Front Characteristics and the Kinematics Associated with Interacting Thunderstorm Outflows

Mahoney, William P.

doi:10.1175/1520-0493(1988)116<1474:gfcatk>2.0.co;2

Cited by 89 publications

(58 citation statements)

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“…Such prefrontal structures have also been detected in observations (e.g., Lawson 1971;Idso et al 1972;Charba 1974;Goff 1976;Mahoney 1988) and numerical simulations (e.g., Mitchell and Hovermale 1977) of thunderstorm gust fronts, which have been related to density current dynamics. Such an overhanging nose structure has been attributed to surface friction (e.g., Simpson 1972;Mitchell and Hovermale 1977) and would also appear to be relevant to cold fronts acting like density currents.…”

Section: E Surface Frictionmentioning

confidence: 59%

“…Some of these proposed mechanisms for the occurrence of prefrontal troughs and wind shifts (discussed more fully in section 3) operate on the synoptic scale (through quasigeostrophic principles) and some operate on the mesoscale. Even smaller-scale fronts not associated with extratropical cyclones are also known to possess troughs in the warm air, such as thunderstorm gust fronts (e.g., Charba 1974;Goff 1976;Mahoney 1988) and sea breezes (e.g., Geisler and Bretherton 1969;Alpert and Rabinovich-Hadar 2003).…”

Section: Characteristics Of Prefrontal Featuresmentioning

confidence: 99%

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A Review of Cold Fronts with Prefrontal Troughs and Wind Shifts

Schultz

2005

Monthly Weather Review

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The conceptual model of a classical surface-based cold front consists of a sharp temperature decrease coincident with a pressure trough and a distinct wind shift at the surface. Many cold fronts, however, do not conform to this model-time series at a single surface station may possess a pressure trough and wind shift in the warm air preceding the cold front (hereafter called a prefrontal trough and prefrontal wind shift, respectively). Although many authors have recognized these prefrontal features previously, a review of the responsible mechanisms has not been performed to date. This paper presents such a review. Ten disparate mechanisms with different frontal structures have been identified from the previous literature. These mechanisms include those external to the front (i.e., those not directly associated with the cold front itself): synoptic-scale forcing, interaction with lee troughs/drylines, interaction with fronts in the mid-and upper troposphere, and frontogenesis associated with inhomogeneities in the prefrontal air. Mechanisms internal to the front (i.e., those directly associated with the structure and dynamics of the front) include the following: surface friction, frontogenesis acting on alongfront temperature gradients, moist processes, descent of air, ascent of air at the front, and generation of prefrontal bores/gravity waves. Given the gaps in our knowledge of the structure, evolution, and dynamics of surface cold fronts, this paper closes with an admonition for improving the links between theory, observations, and modeling to advance understanding and develop better conceptual models of cold fronts, with the goal of improving both scientific understanding and operational forecasting.

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Section: E Surface Frictionmentioning

confidence: 59%

Section: Characteristics Of Prefrontal Featuresmentioning

confidence: 99%

A Review of Cold Fronts with Prefrontal Troughs and Wind Shifts

Schultz

2005

Monthly Weather Review

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“…The propaqatinq qravity waves seen by Ley and Peltier (1981) had a 10 km horizontal wave1enqth, moved at 12 ± 5 m s-l, and caused banded clouds to form when they moved into a favorable environment several hundred kilometers from the apparent source, a severe thunderstorm. Data obtained from dual-Doppler radar analyses suqqest qravity waves may initiate and enhance convection a10nq co11idinq outflow boundaries (Mahoney 1988). …”

Section: Statement By Authormentioning

confidence: 99%

Tropical Squall Lines of the Arizona Monsoon

Smith

Gall

1989

Mon. Wea. Rev.

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“…Mesoscale atmospheric processes such as topographic gravity waves and moist convection are also important contributors to wind variability. Gusty winds can be generated by topographic gravity waves near mountain downslopes (Durran, 1990), or in thunderstorm outflows over land and ocean (Mahoney, 1988) where strong downdrafts (cold pools) occur in association with strong precipitation events (Zeng et al, 2002;Feng et al, 2015). Jabouille et al (1996) showed that wind gusts generated by convective outflow can significantly enhance the surface heat fluxes.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5

et al. 2016

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Abstract. This paper evaluates the impact of sub-grid variability of surface wind on sea salt and dust emissions in the Community Atmosphere Model version 5 (CAM5). The basic strategy is to calculate emission fluxes multiple times, using different wind speed samples of a Weibull probability distribution derived from model-predicted grid-box mean quantities.In order to derive the Weibull distribution, the sub-grid standard deviation of surface wind speed is estimated by taking into account four mechanisms: turbulence under neutral and stable conditions, dry convective eddies, moist convective eddies over the ocean, and air motions induced by mesoscale systems and fine-scale topography over land. The contributions of turbulence and dry convective eddy are parameterized using schemes from the literature. Wind variabilities caused by moist convective eddies and fine-scale topography are estimated using empirical relationships derived from an operational weather analysis data set at 15 km resolution. The estimated sub-grid standard deviations of surface wind speed agree well with reference results derived from 1 year of global weather analysis at 15 km resolution and from two regional model simulations with 3 km grid spacing.The wind-distribution-based emission calculations are implemented in CAM5. In terms of computational cost, the increase in total simulation time turns out to be less than 3 %. Simulations at 2 • resolution indicate that sub-grid wind variability has relatively small impacts (about 7 % increase) on the global annual mean emission of sea salt aerosols, but considerable influence on the emission of dust. Among the considered mechanisms, dry convective eddies and mesoscale flows associated with topography are major causes of dust emission enhancement. With all the four mechanisms included and without additional adjustment of uncertain parameters in the model, the simulated global and annual mean dust emission increase by about 50 % compared to the default model. By tuning the globally constant dust emission scale factor, the global annual mean dust emission, aerosol optical depth, and top-of-atmosphere radiative fluxes can be adjusted to the level of the default model, but the frequency distribution of dust emission changes, with more contribution from weaker wind events and less contribution from stronger wind events. In Africa and Asia, the overall frequencies of occurrence of dust emissions increase, and the seasonal variations are enhanced, while the geographical patterns of the emission frequency show little change.

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Gust Front Characteristics and the Kinematics Associated with Interacting Thunderstorm Outflows

Cited by 89 publications

References 0 publications

A Review of Cold Fronts with Prefrontal Troughs and Wind Shifts

A Review of Cold Fronts with Prefrontal Troughs and Wind Shifts

Tropical Squall Lines of the Arizona Monsoon

Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5

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