A Case of Downstream Baroclinic Development over Western North America

Orlanski, Isidoro; Sheldon, J.

doi:10.1175/1520-0493(1993)121<2929:acodbd>2.0.co;2

Cited by 79 publications

(44 citation statements)

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“…Thus, it is not surprising that, after the remnants of Nuri developed explosively, a preexisting weak blocking event intensified (characterized as "strong," blocking index was 4.12 using the [23] definition) which persisted for 12 days. The blocking event induced troughing and colder conditions over North America during November 2014 (e.g., [59]). Typhoon Nuri and the chain of events that followed during November may have set the flow regime pattern for the entire winter of 2014-2015 over eastern North America [52,60] which was colder than normal especially in the central USA and a harbinger of the repeat of a colder winter like 2013-2014 [24] for 2014-2015.…”

Section: Discussionmentioning

confidence: 99%

The Utility of the Bering Sea and East Asia Rules in Long-Range Forecasting

Renken

Herman²,

Bradshaw

et al. 2017

Advances in Meteorology

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the utility of the Bering Sea Rule (BSR) and the East Asia Rule (EAR) for making forecasts in the two-to-four-week time frame for the central USA region is examined. It is demonstrated using autocorrelation and Fourier transforms that there may be a degree of predictability in this time frame using the PNA, another teleconnection index, or some variation of them. Neither the BSR nor EAR based forecasts showed skill over climatology in the traditional sense, but using signal detection techniques these indexes were skillful at predicting the onset of anomalous temperature conditions (greater than two standard deviations) in the central USA. The BSR generally produced better results that the EAR and formulae for each index are proposed. Three case studies demonstrate the efficacy of these indexes for forecasting temperatures in the central USA. Then, it is proposed that the success of these indexes is likely due to a strong, quasistationary, and persistent Rossby wave train in the Pacific teleconnection region.

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Section: Discussionmentioning

confidence: 99%

The Utility of the Bering Sea and East Asia Rules in Long-Range Forecasting

Renken

Herman²,

Bradshaw

et al. 2017

Advances in Meteorology

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“…Thus, the wave energy flux in (4.1) is c 2 h 0 u 0 . This energy flux is degenerate in the sense that any rotational gauge can be added to the flux without changing the energy equation (e.g., Longuet-Higgins 1964;Pedlosky 1987;Orlanski and Sheldon 1993;Chang and Orlanski 1994). For statistically steady wave solutions, the time derivative vanishes and the divergence of the energy flux is balanced by frictional energy dissipation.…”

Section: Energeticsmentioning

confidence: 99%

Propagation of Meridional Circulation Anomalies along Western and Eastern Boundaries

Marshall

Johnson

2013

Journal of Physical Oceanography

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Motivated by the adjustment of the meridional overturning circulation to localized forcing, solutions are presented from a reduced-gravity model for the propagation of waves along western and eastern boundaries. For wave periods exceeding a few months, Kelvin waves play no role. Instead, propagation occurs through short and long Rossby waves at the western and eastern boundaries, respectively: these Rossby waves propagate zonally, as predicted by classical theory, and cyclonically along the basin boundaries to satisfy the no-normal flow boundary condition. The along-boundary propagation speed is cL d /d, where c is the internal gravity/Kelvin wave speed, L d is the Rossby deformation radius, and d is the appropriate frictional boundary layer width. This result holds across a wide range of parameter regimes, with either linear friction or lateral viscosity and a no-slip boundary condition. For parameters typical of contemporary ocean climate models, the propagation speed is coincidentally close to the Kelvin wave speed. In the limit of weak dissipation, the western boundary wave dissipates virtually all of its energy as it propagates toward the equator, independent of the dissipation coefficient. In contrast, virtually no energy is dissipated in the eastern boundary wave. The importance of background mean flows is also discussed.

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“…This local perspective on the energetics has been strongly fostered by a series of publications by Orlanski (Orlanski and Katzfey, 1991;Orlanski and Chang, 1993;Orlanski and Sheldon, 1993), culminating in a conclusive paper in which the paradigm of (up-and) downstream development of baroclinic waves by ageostrophic geopotential fluxes was introduced (Orlanski and Sheldon, 1995). Its main idea is that downstream disturbances are initiated by the convergence of ageostrophic geopotential fluxes at upper levels before the onset of baroclinic conversion.…”

Section: Introductionmentioning

confidence: 99%

Development of an idealised downstream cyclone: Eulerian and Lagrangian perspective on the kinetic energy

Papritz

Schemm

2013

Tellus A: Dynamic Meteorology and Oceanography

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A B S T R A C TIn this idealised modelling study, the development of a downstream cyclone, which closely follows the life-cycle of a Shapiro-Keyser cyclone, is addressed from a quasi-geostrophic kinetic energy perspective. To this end a simulation of a dry, highly idealised, dispersive baroclinic wave, developing a primary and a downstream cyclone, is performed. Kinetic energy and processes contributing to its tendency Á in particular baroclinic conversion and ageostrophic geopotential fluxes Á are investigated in three dimensions both in an Eulerian and a Lagrangian framework from the genesis of the downstream cyclone as an upper-level kinetic energy centre, over frontal fracture to the fully developed cyclone showing the characteristic T-bone surface frontal structure, with a strong low-level jet along the bent-back front. Initially the downstream cyclone grows by the convergence of ageostrophic geopotential fluxes from the primary cyclone, but as vertical motions intensify this process is replaced by baroclinic conversion in the warm sector. We show that kinetic energy released in the warm sector is radiated away at all levels by ageostrophic geopotential fluxes: in the upper troposphere they are directed downstream, while in the lower troposphere they radiate kinetic energy to the rear of the cyclone. Thereby, vertical ageostrophic geopotential fluxes, their location and divergence, are identified to play a major role in the intensification of the cyclone in the lower troposphere and for the formation of the low-level jet. Low-level rearward ageostrophic geopotential fluxes converging along the bent-back front are shown to be a general characteristic of an eastward propagating baroclinic wave.

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A Case of Downstream Baroclinic Development over Western North America

Cited by 79 publications

References 0 publications

The Utility of the Bering Sea and East Asia Rules in Long-Range Forecasting

The Utility of the Bering Sea and East Asia Rules in Long-Range Forecasting

Propagation of Meridional Circulation Anomalies along Western and Eastern Boundaries

Development of an idealised downstream cyclone: Eulerian and Lagrangian perspective on the kinetic energy

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