Linear Simulation of the Stationary Eddies in a General Circulation Model. Part I: The No-Mountain Model

Nigam, Sumant; Held, Isaac M.; Lyons, Steven W.

doi:10.1175/1520-0469(1986)043<2944:lsotse>2.0.co;2

Cited by 49 publications

(30 citation statements)

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“…Ting (1994) addresses the question of summertime stationary wave orographic interaction using a GCM and a linear baroclinic model. The linear model is similar to that used by Nigam et al (1986Nigam et al ( , 1988 to interpret the GCM generated stationary waves, from a linearized form of the GCM equations. This dynamical diagnosis allows for apportionment of wave forcing: Heating, orography and transient/eddy fluxes.…”

Section: Large Scale Variabilitymentioning

confidence: 99%

Variability of the Great Plains Low-Level Jet: Large-Scale Circulation Context and Hydroclimate Impacts

2008

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Variability of the Great Plains Low-Level Jet (GPLLJ) is analyzed from the perspective of larger-scale, lower-frequency influences and regional hydroclimate impacts; as opposed to the usual analysis of its frequency, diurnal variability and mesoscale structure.The circulation-centric core analysis is conducted with monthly and pentad data from the high spatio-temporal resolution, precipitation-assimilating North American Regional Reanalysis, and ERA-40 global reanalysis (as necessary) to identify the recurrent patterns of GPLLJ variability and their large-scale circulation and regional hydroclimate links.The analysis reveals that GPLLJ variability is, indeed, linked to coherent, largescale, upper-level height patterns over the Pacific, and NAO variability in the Atlantic. A Rossby Wave Source analysis shows the Pacific height pattern to be potentially linked to tropical diabatic heating anomalies in the west-central basin and in the eastern Pacific sector. EOF analysis of GPLLJ variability shows it to be comprised of three modes that exert profound influence on Great Plains precipitation variability, and together, account for ~75% of the variance.Ocean basin centered EOF analysis on summertime SLP anomalies shows similar GPLLJ and precipitation impacts as those found in the Great Plains centric perspective, supporting the claim for remotely generated influences on Great Plains low-level jet and hydroclimate variability.Pentad analysis of the atmospheric and terrestrial water balances during the 1988 drought and 1993 flood show that, jet variability, while influential over many of the subseasonal anomalous precipitation episodes was not a necessary condition for precipitation anomalies. Great Plains evaporation exhibited a 2-week delay with respect to precipitation suggesting a minor role for precipitation recycling during these events. ENSO and NAO variability are shown to contribute significantly to the large midsummer positive precipitation anomalies during 1993.EEOF analysis of pentad 900 hPa meridional winds during MJJ show three temporally stable modes of variability, each exhibiting similar spatial characteristics to the monthly EOF spatial patterns. Lead/lag regressions show a one pentad delay in moisture flux convergence generated precipitation anomalies, perhaps, suggesting the importance of moisture transports in generating Great Plains precipitation anomalies.Climate models are shown to be challenged in depicting the jet and precipitation variability over the Great Plains.

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Section: Large Scale Variabilitymentioning

confidence: 99%

Variability of the Great Plains Low-Level Jet: Large-Scale Circulation Context and Hydroclimate Impacts

2008

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“…The Plumb flux diagnostic of stationary wave activity, presented here as a unit vector (unitless), is sensitive to the tropics-to-extratropics Rossby wave propagation from a tropical heating source and, thus, is useful in revealing remote forcings (Karoly et al 1989;Barlow et al 2001). The atmospheric stationary waves in the tropics are driven by the divergent circulation which is maintained largely through diabatic heating (Krishnamurti 1971;Nigam et al 1986). To illustrate the role of diabatic heating in the divergent circulation, we used the following velocity potential (v) maintenance equation, which is derived from the combination of the thermodynamic and continuity equations (Chen and Yen 1991):…”

Section: Diagnostic Schemes For Large-scale Circulationmentioning

confidence: 99%

A transition-phase teleconnection of the Pacific quasi-decadal oscillation

et al. 2010

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The atmospheric circulation patterns associated with the Pacific quasi-decadal oscillation (QDO) are investigated using available observational data from 1948 to 2007. Previous studies indicate that the Pacific QDO is characterized by a distinct lifecycle in the form of sea surface temperature (SST) patterns. In the warm and cool phases of the Pacific QDO, the SST patterns resemble those associated with the El Niño-Southern Oscillation (ENSO). During the warm-cool and cool-warm transitions of the Pacific QDO, recurrent SST patterns are also clearly visible. The rotated empirical orthogonal function analysis on the 10-15 year filtered data shows that the evolutions of SST and atmospheric circulation are well coupled. While the warm-/cool-phase Pacific QDO generates an ENSOlike circulation pattern, the transition phases form a distinct short-wave train emanating from Southeast Asia towards North America. This short-wave train is particularly robust in the streamfunction of water vapor flux. Diagnostic analyses of the heat budget, the stationary wave flux, and a barotropic model indicate that this short-wave train is thermodynamically maintained and is likely forced by diabatic heating near Southeast Asia. Additional modulations of forcing sources in the western and eastern tropical Pacific on this short-wave teleconnection are also discussed.

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“…Changes in surface heat capacity can also have a profound impact on the surface sensible and latent heat fluxes and consequently the diabatic heating higher in the tropical troposphere. Such responses have been studied through tropical SST anomaly experiments (e.g., Neale and Hoskins 2000b) and tropospheric heating anomalies (e.g., Gill 1980;Jin and Hoskins 1995), which are capable of radiating Rossby waves poleward and eastward into the midlatitudes (Sardeshmukh and Hoskins 1988;Hoskins and Karoly 1981), although the signal produced by changes in the properties of the tropical land surface can be quite weak, particularly in the lower troposphere (Brankovic et al 2006;Zhang et al 1996;Valdes and Hoskins 1989;Nigam et al 1986). …”

Section: Introductionmentioning

confidence: 99%

“…Heating and orographic anomalies are then introduced and the steady-state response in the flow diagnosed. This method has been used to great effect by many authors (e.g., Held et al 2002;Valdes and Hoskins 1989;Nigam et al 1986;Hoskins and Karoly 1981). However, these models have three principal limitations.…”

Section: Introductionmentioning

confidence: 99%

The Basic Ingredients of the North Atlantic Storm Track. Part I: Land–Sea Contrast and Orography

Brayshaw

Hoskins

Blackburn

2009

Journal of the Atmospheric Sciences

150

147

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Understanding and predicting changes in storm tracks over longer time scales is a challenging problem, particularly in the North Atlantic. This is due in part to the complex range of forcings (land-sea contrast, orography, sea surface temperatures, etc.) that combine to produce the structure of the storm track. The impact of land-sea contrast and midlatitude orography on the North Atlantic storm track is investigated through a hierarchy of GCM simulations using idealized and ''semirealistic'' boundary conditions in a highresolution version of the Hadley Centre atmosphere model (HadAM3). This framework captures the largescale essence of features such as the North and South American continents, Eurasia, and the Rocky Mountains, enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies. The physical processes by which the forcing mechanisms impact the large-scale flow and the midlatitude storm tracks are discussed. The characteristics of the North American continent are found to be very important in generating the structure of the North Atlantic storm track. In particular, the southwest-northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the Rocky Mountains leads to enhanced storm development along an axis close to that of the continent's eastern coastline. The approximately triangular shape of North America also enables a cold pool of air to develop in the northeast, intensifying the surface temperature contrast across the eastern coastline, consistent with further enhancements of baroclinicity and storm growth along the same axis.

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Linear Simulation of the Stationary Eddies in a General Circulation Model. Part I: The No-Mountain Model

Cited by 49 publications

References 0 publications

Variability of the Great Plains Low-Level Jet: Large-Scale Circulation Context and Hydroclimate Impacts

Variability of the Great Plains Low-Level Jet: Large-Scale Circulation Context and Hydroclimate Impacts

A transition-phase teleconnection of the Pacific quasi-decadal oscillation

The Basic Ingredients of the North Atlantic Storm Track. Part I: Land–Sea Contrast and Orography

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