Quasigeostrophic Vertical Motions Diagnosed from Along- and Cross-isentrope Components of the Q Vector

Keyser, Daniel; Schmidt, Brian D.; Duffy, Dean G.

doi:10.1175/1520-0493(1992)120<0731:qvmdfa>2.0.co;2

Cited by 56 publications

(39 citation statements)

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“…In those studies, as in this one, the contributions of the transverse vertical motions to the processes in question gradually increased as frontal structures began to take shape. This similarity suggests that the shearwise vertical motions, what Keyser et al (1992) referred to as wave-scale vertical motions, and the associated process of rotational frontogenesis play a primary role in moulding the large-scale flow into some of the basic synoptic-scale structures involved in the production of sensible weather in the extratropics.…”

Section: Discussionmentioning

confidence: 95%

“…Taking up the suggestion made by Keyser et al (1988), who noted that the so-called Q vector, introduced by Hoskins et al (1978), was the QG form of (1), Keyser et al (1992) applied the quasi-geostrophic (QG) assumption to F. Exploiting the fact that for horizontal adiabatic flow,…”

Section: Vector Frontogenesis and Vertical Motionmentioning

confidence: 99%

“…The diagnostic tool by which this interpretation is advanced is the partitioned quasigeostrophic (QG) Q-vector approach first suggested by Keyser et al (1988), and explored more thoroughly by Keyser et al (1992). As will be shown later, this approach allows the discrete vertical circulations associated with changes in the magnitude and direction of ∇θ (the socalled scalar and rotational frontogenesis, respectively) to be isolated.…”

Section: Introductionmentioning

confidence: 99%

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The influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper‐level front

Lang

Martin

2010

Quart J Royal Meteoro Soc

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The total quasi-geostrophic (QG) vertical motion is partitioned into transverse and shearwise couplets oriented parallel to, and along, the geostrophic vertical shear, respectively, in order to examine the role of rotational frontogenesis, and its associated shearwise circulation, in the life cycle of an upper-front/jet system in northwesterly flow. In particular the analysis emphasizes two aspects of that role: (1) the influence of shearwise ω on scalar frontogenesis, and (2) the effect of rotational frontogenesis, and its associated vertical circulation, on the initiation of along-flow cold air advection during upper frontogenesis.The case-study analysis reveals that shearwise subsidence persistently and significantly contributes to scalar frontogenesis throughout the life cycle. The transverse subsidence contribution to scalar frontogenesis is initially weak but grows more substantial after the establishment of along-flow cold air advection near the base of the thermal trough.Prior work has argued that the development of along-flow cold air advection arises from a cyclonic rotation of ∇θ promoted either by contributions from tilting or horizontal kinematics. From the QG perspective adopted in the present study, the tilting and kinematic rotations are seen as interconnected aspects of a single, underlying dynamical process: rotational frontogenesis, in which the rotation of ∇θ produced by vertical vorticity is accompanied by a discrete vertical circulation (the shearwise circulation) that provides the subsidence upshear of the vorticity maximum required to initiate along-flow cold air advection. It is further suggested that the characteristic distribution of the kinematic and tilting contributions to rotation of ∇θ in the vicinity of an upper-tropospheric vorticity maximum underlies the observed preference for the development of upper-level fronts in northwesterly flow.

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Section: Discussionmentioning

confidence: 95%

Section: Vector Frontogenesis and Vertical Motionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper‐level front

Lang

Martin

2010

Quart J Royal Meteoro Soc

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“…Previous studies (Keyser et al, 1988(Keyser et al, , 1992Martin, 1999Martin, , 2007Yue et al, 2003Yue et al, , 2011 have shown that partitioning of the Q Q Q vector can provide useful information about the forcing from multi-scale weather systems. The Q Q Q vector is often decomposed into two components: one along the direction of potential temperature (Q Q Q s ) and the other along the direction of the potential temperature gradient (Q Q Q n ).…”

Section: Q Vector Partitioningmentioning

confidence: 99%

A diagnostic study of the asymmetric distribution of rainfall during the landfall of typhoon Haitang (2005)

et al. 2015

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The precipitation during landfall of typhoon Haitang (2005) showed asymmetric structures (left side/right side of the track). Analysis of Weather Research and Forecasting model simulation data showed that rainfall on the right side was more than 15 times stronger than on the left side. The causes were analyzed by focusing on comparing the water vapor flux, stability and upward motion between the two sides. The major results were as follows: (1) Relative humidity on both sides was over 80%, whereas the convergence of water vapor flux in the lower troposphere was about 10 times larger on the right side than on the left side.(2) Both sides featured conditional symmetric instability [MPV (moist potential vorticity) <0], but the right side was more unstable than the left side. (3) Strong (weak) upward motion occurred throughout the troposphere on the right (left) side. The Q Q Q vector diagnosis suggested that large-scale and mesoscale forcing accounted for the difference in vertical velocity. Orographic lift and surface friction forced the development of the asymmetric precipitation pattern. On the right side, strong upward motion from the forcing of different scale weather systems and topography caused a substantial release of unstable energy and the transportation of water vapor from the lower to the upper troposphere, which produced torrential rainfall. However, the above conditions on the left side were all much weaker, which led to weaker rainfall. This may have been the cause of the asymmetric distribution of rainfall during the landfall of typhoon Haitang.Citation: Yue, C. J., S. T. Gao, L. Liu, and X. F. Li, 2015: A diagnostic study of the asymmetric distribution of rainfall during the landfall of typhoon Haitang (2005).

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“…Sanders and Hoskins (1990) provided a method for easy estimation of Q vectors from weather maps, which was used to verify the results presented herein. Keyser et al (1992) used numerical simulations to determine how well Q-vector divergence relates to quasigeostrophic vertical motion and were able to show how significant the Q vector is in diagnosing synoptic events.…”

Section: B Diagnostic Variablesmentioning

confidence: 99%

Statistical Differences of Quasigeostrophic Variables, Stability, and Moisture Profiles in North American Storm Tracks

Mercer

Richman

2007

Monthly Weather Review

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Three common synoptic storm tracks observed throughout the United States are the Alberta Clipper, the Colorado cyclone, and the East Coast storm. Numerous studies have been performed on individual storm tracks analyzing quasigeostrophic dynamics, stability, and moisture profiles in each. This study evaluated storms in each track to help diagnose patterns and magnitudes of the aforementioned quantities, documenting how they compare from track to track. Six diagnostic variables were computed to facilitate the comparison of the storm tracks: differential geostrophic absolute vorticity advection, temperature advection, Q-vector divergence, mean layer specific humidity, low-level stability, and midlevel stability. A dataset was compiled, consisting of 101 Alberta Clippers, 165 Colorado cyclones, and 159 East Coast cyclones and mean fields were generated for this comparison. Maxima and minima of the 25th and 75th percentiles were generated to diagnose magnitudes and patterns of strong versus weak cyclones and measure their similarities and differences to the mean patterns. Alberta Clippers were found to show the weakest magnitude of quasigeostrophic variables, while East Coast storms had the strongest magnitudes. Alberta Clippers maintained the lowest moisture content through their life cycle as well. However, East Coast storms were the most stable of the three tracks. Typically, correlations between storm tracks were high; suggesting that storm evolution is similar between tracks, in terms of the patterns of diagnostic variables measured. However, significant magnitude differences in the quasigeostrophic variables distinguished the storms in each track.

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Quasigeostrophic Vertical Motions Diagnosed from Along- and Cross-isentrope Components of the Q Vector

Cited by 56 publications

References 0 publications

The influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper‐level front

The influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper‐level front

A diagnostic study of the asymmetric distribution of rainfall during the landfall of typhoon Haitang (2005)

Statistical Differences of Quasigeostrophic Variables, Stability, and Moisture Profiles in North American Storm Tracks

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