Factors Affecting Surface Wind Speeds in Gravity Waves and Wake Lows

Coleman, Timothy A.; Knupp, Kevin R.

doi:10.1175/2009waf2222248.1

Cited by 11 publications

(5 citation statements)

References 32 publications

(42 reference statements)

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“…including the parts of the lulls extending beyond the boundaries of the WDA, was from 1250 to 1330, corresponding roughly to the duration of the positive surface-pressure anomaly. The wind-speed component in the direction of the southwesterly system velocity is well correlated with the surface pressure anomaly (a correlation coefficient of 0.78 for 1245 to 1345) as expected from Coleman and Knupp (2009). These anomalies will be shown to be closely associated with, and probably largely due to, the wave in the cool undercurrent.…”

Section: Surface Observations During the Passage Of The Mcssupporting

confidence: 58%

Multi-sensor observations of a wave beneath an impacting rear-inflow jet in an elevated mesoscale convective system

Marsham

Browning

Nicol

et al. 2010

Q.J.R. Meteorol. Soc.

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Observations of a wave generated below, and propagating with, an elevated mesoscale convective system (MCS) are presented. The MCS and the wave tracked directly across the 90 km extent of the observational network deployed for the Convective Storm Initiation Project (CSIP) and maintained a coherent structure and velocity during this 1.5 hour period. The rear-inflow jet of the MCS was observed to impact upon, but not penetrate, the stable undercurrent that was located beneath the MCS, apparently constricting the depth of the undercurrent, which did not participate in the main convective updraught.

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Section: Surface Observations During the Passage Of The Mcssupporting

confidence: 58%

Multi-sensor observations of a wave beneath an impacting rear-inflow jet in an elevated mesoscale convective system

Marsham

Browning

Nicol

et al. 2010

Q.J.R. Meteorol. Soc.

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“…Of interest is the fact that the pressure couplet defined by the wake low and mesohigh largely exhibits positive p′-u′ correlation as is characteristic of MGWs, as noted earlier (Koch and Siedlarz 1999;Coleman and Knupp 2009). The interpretation of the wake low-mesohigh couplet as a gravity wave is further supported by the idealized linear modeling study of Haertel and Johnson (2000), which demonstrated that an imposed stratiform-like forcing characterized by latent cooling alone can excite a gravity wave response consistent with a mesohigh-wake low couplet.…”

Section: Wave Amplification: the Role Of Moist Convectionmentioning

confidence: 55%

“…Another pattern that emerges from a review of many large-amplitude MGW events is the strong parallel between MGWsespecially singular waves of depressionand squall line wake low-mesohigh couplets (Bosart and Seimon 1988;Koch et al 1988;Koch and Siedlarz 1999;Coleman andKnupp 2009, 2011;Ruppert and Bosart 2014). This conceptual framework is schematically depicted in Fig.…”

Section: Wave Amplification: the Role Of Moist Convectionmentioning

confidence: 99%

Mesoscale Gravity Waves and Midlatitude Weather: A Tribute to Fuqing Zhang

Ruppert

Koch

Chen

et al. 2022

Bulletin of the American Meteorological Society

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Over the course of his career, Fuqing Zhang drew vital new insights into the dynamics of meteorologically significant mesoscale gravity waves (MGWs), including their generation by unbalanced jet streaks, their interaction with fronts and organized precipitation, and their importance in midlatitude weather and predictability. Zhang was the first to deeply examine “spontaneous balance adjustment” – the process by which MGWs are continuously emitted as baroclinic growth drives the upper-level flow out of balance. Through his pioneering numerical model investigation of the large-amplitude MGW event of 4 January 1994, he additionally demonstrated the critical role of MGW–moist convection interaction in wave amplification.Zhang’s curiosity-turned-passion in atmospheric science covered a vast range of topics and led to the birth of new branches of research in mesoscale meteorology and numerical weather prediction. Yet, it was his earliest studies into midlatitude MGWs and their significant impacts on hazardous weather that first inspired him. Such MGWs serve as the focus of this review, wherein we seek to pay tribute to his groundbreaking contributions, review our current understanding, and highlight critical open science issues. Chief among such issues is the nature of MGW amplification through feedback with moist convection, which continues to elude our understanding. The pressing nature of this subject is underscored by the continued failure of operational numerical forecast models to adequately predict most large-amplitude MGW events. Further research into such issues therefore presents a valuable opportunity to improve the understanding and forecasting of this high-impact weather phenomenon, and in turn to preserve the spirit of Zhang’s dedication to this subject.

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“…The correlation between wind perturbations and pressure perturbations in disturbances such as gravity waves (e.g., Coleman and Knupp 2009;Trexler and Koch 2000;Bosart and Sanders 1986) is consistent with this relationship. The classical impedance relation may be derived by linearizing the horizontal momentum equation at the surface (where w 5 0), and then integrating this equation over time in a propagating, form-preserving disturbance in pressure.…”

Section: Introductionmentioning

confidence: 60%

A Nonlinear Impedance Relation for the Surface Winds in Pressure Disturbances

Coleman

Knupp

2010

Journal of the Atmospheric Sciences

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The ''impedance relation'' between the wind perturbation within an ageostrophic atmospheric disturbance and its pressure perturbation and intrinsic propagation speed has been in use for decades. The correlation between wind and pressure perturbation was established through this relation. However, a simple Lagrangian model of an air parcel traversing an idealized sinusoidal wave in the pressure field indicates that the impedance relation produces significant errors. Examination of the nonlinearized horizontal momentum equation with a sinusoidal disturbance in pressure reveals an additional nonlinear term in the impedance relation, not previously included.In this paper, the impedance relation is rederived, with the solution being the original equation with the addition of the nonlinear term. The new equation is then evaluated against the Lagrangian model of an air parcel traversing an idealized gravity wave, as well as three observed cases. It is shown that the new impedance relation is indeed more accurate in predicting wind perturbations in disturbances based on pressure perturbations and intrinsic speed than the accepted equation. Implications for determination of the intrinsic phase speed of a disturbance when pressure and wind perturbations are known (another widely used application of the impedance relation) are also discussed.

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Factors Affecting Surface Wind Speeds in Gravity Waves and Wake Lows

Cited by 11 publications

References 32 publications

Multi-sensor observations of a wave beneath an impacting rear-inflow jet in an elevated mesoscale convective system

Multi-sensor observations of a wave beneath an impacting rear-inflow jet in an elevated mesoscale convective system

Mesoscale Gravity Waves and Midlatitude Weather: A Tribute to Fuqing Zhang

A Nonlinear Impedance Relation for the Surface Winds in Pressure Disturbances

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