Jet Streak Dynamics and Geostrophic Adjustment Processes during the Initial Stages of Lee Cyclogenesis

Mattocks, Craig; Bleck, Rainer

doi:10.1175/1520-0493(1986)114<2033:jsdaga>2.0.co;2

Cited by 47 publications

(28 citation statements)

References 7 publications

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“…The GBCZ is the dominant surface feature during cyclogenesis but, unlike a classic lee trough, is oriented normal to the Sierra Nevada. Future work should examine the mechanisms responsible for the GBCZ and determine if IC evolution might be better conceptualized from a PV perspective, possibly involving an adaptation of the Mattocks and Bleck (1986) model of Alpine lee cyclogenesis.…”

Section: Discussionmentioning

confidence: 99%

“…Instead, we propose that IC genesis might be better conceptualized through an adaptation of the Mattocks and Bleck (1986) model of Alpine lee cyclogenesis. In their model, the Alps block the movement of an impinging low-level cold front as an upper-level trough and cyclonic PV anomaly move relatively unimpeded into the lee.…”

Section: O N T H L Y W E a T H E R R E V I E W Volume 138mentioning

confidence: 99%

“…downstream of the high Sierra. This represents an additional surface (i.e., surrogate) PV anomaly in the classic PV view of cyclogenesis (Hoskins et al 1985) that is not accounted for by the Mattocks and Bleck (1986) model of Alpine lee cyclogenesis. The third difference is the presence of substantive downstream orography.…”

Section: O N T H L Y W E a T H E R R E V I E W Volume 138mentioning

confidence: 99%

“…The third difference is the presence of substantive downstream orography. Future work could use a similar modeling strategy to Mattocks and Bleck (1986), but with a mountain barrier oriented like the Sierra Nevada, to develop a dynamically based conceptual model for IC genesis and perhaps provide a robust comparison with Alpine lee cyclogenesis. This work could also explore how IC life cycles are modified by downstream orography.…”

Section: O N T H L Y W E a T H E R R E V I E W Volume 138mentioning

confidence: 99%

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Multi-Reanalysis Climatology of Intermountain Cyclones

Jeglum

Steenburgh

Lee

et al. 2010

Monthly Weather Review

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The topography in and around the Intermountain West strongly affects the genesis, migration, and lysis of extratropical cyclones. Here intermountain (i.e., Nevada or Great Basin) cyclone (IC) activity and evolution are examined using the ECMWF Re-Analysis Interim (ERA-Interim) the North American Regional Reanalysis (NARR), and the NCEP-NCAR reanalysis from 1989 to 2008, the period during which all three are available. The ICs are defined and tracked objectively as 850-hPa geopotential height depressions of $40 m that persist for $12 h.The monthly distribution of IC center and genesis frequency in all three reanalyses is bimodal with spring (absolute) and fall (secondary) maxima. Although the results are sensitive to differences in resolution, topographic representation, and reanalysis methodology, both the ERA-Interim and NARR produce frequent IC centers and genesis in the Great Basin cyclone region, which extends from the southern ''high'' Sierra to northwest Utah, and the Canyonlands cyclone region, which lies over the upper Colorado River basin of southeast Utah. The NCEP-NCAR reanalysis fails to resolve these two distinct cyclone regions and produces less frequent IC centers and genesis than the ERA-Interim and NARR.An ERA-Interim-based composite of strong ICs generated in cross-Sierra (2108-3008) 500-hPa flow shows that cyclogenesis is preceded by the development of the Great Basin confluence zone (GBCZ), a regional airstream boundary that extends downstream from the Sierra Nevada across the Intermountain West. Cyclogenesis occurs along the GBCZ as large-scale ascent develops over the Intermountain West in advance of an approaching upper-level trough. Flow splitting around the high Sierra and the presence of low-level baroclinicity along the GBCZ suggest that IC evolution may be better conceptualized from a potential vorticity perspective than from traditional quasigeostrophic models of lee cyclogenesis. Although these results provide new insights into IC activity and evolution, analysis uncertainty and the cyclone identification criteria are important sources of ambiguity that cannot be fully eliminated.

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Section: Discussionmentioning

confidence: 99%

Section: O N T H L Y W E a T H E R R E V I E W Volume 138mentioning

confidence: 99%

Section: O N T H L Y W E a T H E R R E V I E W Volume 138mentioning

confidence: 99%

Section: O N T H L Y W E a T H E R R E V I E W Volume 138mentioning

confidence: 99%

See 2 more Smart Citations

Multi-Reanalysis Climatology of Intermountain Cyclones

Jeglum

Steenburgh

Lee

et al. 2010

Monthly Weather Review

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“…Mattocks and Bleck 1986;Takayabu 1991;Clough et al 1996;Davies and Rossa 1998), although the correspondence between jet streaks and PV maxima is not the primary focus of these investigations. Moreover, the observed signature in the relative-vorticity field associated with many of these PV maxima is that of a cyclonic-anticyclonic dipole (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of jet streaks in a stratified quasi‐geostrophic atmosphere: Steady‐state representations

Cunningham

Keyser

2004

Quart J Royal Meteoro Soc

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SUMMARYThe structure and dynamics of jet streaks in the extratropical upper troposphere are examined in the context of a continuously stratified quasi-geostrophic (QG) framework. It is hypothesized that jet streaks may result from the superposition of monopolar or dipolar vortices of mesoscale dimensions with the enhanced potential-vorticity gradients constituting the tropopause. Based on this hypothesis, steady-state monopolar and dipolar vortices in a uniform zonal background flow on an f -plane are investigated for their applicability as idealized dynamical representations of jet streaks. The representations of jet streaks satisfy the nonlinear governing equations of the continuously stratified QG framework: the monopolar vortex is specified in terms of axisymmetric distributions of QG potential vorticity in the interior of the domain and perturbation potential temperature on upper (tropopause) and lower (surface) boundaries, whereas the dipolar vortex is adapted from a closed-form analytical solution for the geostrophic stream function. Through the incorporation of vertical structure and divergent circulations, these representations of jet streaks extend those presented previously by the authors using a non-divergent barotropic model.It is shown that these vortex representations display characteristic signatures similar to those observed in atmospheric jet streaks. In particular, both the monopole and the dipole exhibit an ageostrophic wind directed towards lower geopotential height in the entrance region of the streak and towards higher geopotential height in the exit region. For the monopole, this ageostrophic wind is entirely rotational and there is no vertical motion. For the dipole, the rotational part of the ageostrophic wind dominates the divergent part; the latter is associated with a four-cell pattern of vertical velocity similar to that described in conceptual models of straight jet streaks. For both the monopole and the dipole, the jet streak is induced by the vortex structure such that the wind speed maximum translates at the same speed as the individual vortices; this translation speed is slower than the maximum wind speed in the core of the speed maximum, consistent with observations of jet streaks.It is proposed that the above representations provide a formal theoretical foundation for the conceptual models of jet streaks prevalent in the literature; these conceptual models typically are based on heuristic kinematic or parcel arguments and not on consistent solutions to a physically plausible set of equations. The representations also provide a foundation upon which to explore the unsteady behaviour of jet streaks in terms of the superposition of monopolar and dipolar vortices with non-uniform zonal background flows.

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Decomposing the role of dry intrusions for ocean evaporation during mistral

Givon,

Keller,

Pennel

et al. 2024

Quart J Royal Meteoro Soc

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The mistral is a northerly gap‐wind regime blowing through the Rhone Valley in Southern France. It is held responsible for the sea‐surface cooling necessary to produce deep convection in the Gulf of Lion through turbulent ocean heat loss. The mistral is tightly connected to lee‐cyclogenesis in the Gulf of Genoa, where topography forces substantial downward motion. Dry intrusions (DIs) are airstreams forming the descending branch of extratropical cyclones. Known to induce cold and dry surface anomalies, DIs are potential contributors to enhanced surface evaporation during mistral. In this study, a climatological database (ERA‐INTERIM, 1981–2016) of mistral–DI co‐occurrence is constructed, allowing quantification of the impact of DIs on the mistral evaporative hot spot for the first time. We find that, on average, mistral–DI evaporation rates are doubled, compared to mistral without DIs. Moreover, cluster‐composite analysis reveals amplifications exceeding 300% between dynamically similar mistral events, with response to DIs. Daily latent heat‐flux anomalies in the Gulf of Lion are decomposed into contributions from the various parameters to analyse the mistral evaporation response to DIs. Mistral–DI events are shown to produce extreme evaporation rates through increased mistral wind speeds. The results highlight the downward momentum flux delivered by DIs to the mistral at the Gulf of Lion as the primary driver of the evaporation amplification mechanism. We further explore the variability between different mistral–DI events and conclude that extreme mistral–DI evaporation events are linked to descending air trajectories entering the Gulf of Lion at an early stage of their lifetimes. These DIs charge the mistral with maximum vertical momentum fluxes, which act to intensify surface winds and hence evaporation rates.

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Jet Streak Dynamics and Geostrophic Adjustment Processes during the Initial Stages of Lee Cyclogenesis

Cited by 47 publications

References 7 publications

Multi-Reanalysis Climatology of Intermountain Cyclones

Multi-Reanalysis Climatology of Intermountain Cyclones

Dynamics of jet streaks in a stratified quasi‐geostrophic atmosphere: Steady‐state representations

Decomposing the role of dry intrusions for ocean evaporation during mistral

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