The Diagnosis of Synoptic-Scale Vertical Motion in an Operational Environment

Durran, Dale R.; Snellman, Leonard W.

doi:10.1175/1520-0434(1987)002<0017:tdossv>2.0.co;2

Cited by 47 publications

(28 citation statements)

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“…In addition, Durran and Snellman (1987) and Clough et al (1996) note that the omega distribution arrived at by the integration of (3) is dominated by longwave forcing aloft, insensitive to low-altitude forcing, and maximized in the midtroposphere (e.g., near 500 hPa). We assume v 5 0 at the lateral boundaries and limit the integration to five midtropospheric levels (700, 600, 500, 400, and 300 hPa) with v 5 0 at 850 and 200 hPa.…”

Section: ) the Alternative Balance (Ab) Omega Equationmentioning

confidence: 99%

The Climatology of Synoptic-Scale Ascent over Western North America: A Perspective on Storm Tracks

Lareau

Horel

2012

Monthly Weather Review

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The position and variability of storm tracks across western North America are examined during the October-April cool seasons spanning 1989-2010. The location and intensity of storms are represented by strong synoptic-scale ascent, which is diagnosed by the alternative balance omega equation applied to ECMWF Re-Analysis Interim data. This dynamically filtered method removes poorly resolved updrafts arising from subsynoptic-scale phenomena such as convection and mountain waves. The resulting vertical motions are illustrated for the case of a strong storm traversing the western United States.Summary statistics of synoptic-scale ascent are compiled over months, seasons, and the entire 21-yr period. Locations exhibiting high mean values of ascent are deemed to represent storm tracks. The climatologicalmean storm track exhibits a sinusoidal shape across the eastern Pacific and western North America. The composite evolution of strong storms moving along specific segments of the storm track show regional differences (e.g., storms poleward of 508N tend to result from progressive low-amplitude troughs progressing through the mean planetary ridge, while storms over the western United States are initiated by digging troughs that temporarily suppress the mean ridge).Seasonal shifts in the storm track are pronounced and exhibit coherent regional patterns. Interannual variations in synoptic-scale ascent indicate meridional shifts in position as well as changes in the degree of amplification within the dominant sinusoidal storm track. These changes in structure are related to the phase of ENSO: El Niñ o (La Niñ a) winters favor zonal (amplified) and southern (northern) storm tracks.

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Section: ) the Alternative Balance (Ab) Omega Equationmentioning

confidence: 99%

The Climatology of Synoptic-Scale Ascent over Western North America: A Perspective on Storm Tracks

Lareau

Horel

2012

Monthly Weather Review

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“…The QG omega equation has been widely used to diagnose synoptic vertical motion (Sutcliffe 1947;Hoskins et al 1978;Trenberth 1978;Durran and Snellman 1987;Raisanen 1995). It indicates the vertical motion induced by geostrophic advection of temperature and vorticity.…”

Section: Warm-air Advectionmentioning

confidence: 99%

Observational Analysis of Heavy Rainfall Mechanisms Associated with Severe Tropical Storm Bilis (2006) after Its Landfall

Shuanzhu

Meng

Zhang

et al. 2009

Monthly Weather Review

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This observational study attempts to determine factors responsible for the distribution of precipitation over large areas of southern China induced by Bilis, a western North Pacific Ocean severe tropical storm that made landfall on the southeastern coast of mainland China on 14 July 2006 with a remnant circulation that persisted over land until after 17 July 2006. The heavy rainfalls associated with Bilis during and after its landfall can be divided into three stages. The first stage of the rainfall, which occurred in Fujian and Zhejiang Provinces, could be directly induced by the inner-core storm circulation during its landfall. The third stage of rainfall, which occurred along the coastal areas of Guangdong and Fujian Provinces, likely resulted from the interaction between Bilis and the South China Sea monsoon enhanced by topographical lifting along the coast. The second stage of the rainfall, which appeared inland around the border regions between Jiangxi, Hunan, and Guangdong Provinces, caused the most catastrophic flooding and is the primary focus of the current study. It is found that during the second stage of the rainfall all three ingredients of deep moist convection (moisture, instability, and lifting) are in place. Several mechanisms, including vertical wind shear, warm-air advection, frontogenesis, and topography, may have contributed simultaneously to the lifting necessary for the generation of the heavy rainfall at this stage.

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“…This equation was also at the core of QG theory from the late 1940s on, and has been used widely in operational meteorology (e.g. Durran and Snellman 1987). That it provides a basis for understanding the dynamics of middle latitude weather systems has been emphasized in a number of dynamical texts (e.g.…”

Section: Introductionmentioning

confidence: 99%

The omega equation and potential vorticity

Hoskins

Pedder

Jones

2003

Quart J Royal Meteoro Soc

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SUMMARYTwo fundamental perspectives on the dynamics of midlatitude weather systems are provided by potential vorticity (PV) and the omega equation. The aim of this paper is to investigate the link between the two perspectives, which has so far received very little attention in the meteorological literature. It also aims to give a quantitative basis for discussion of quasi-geostrophic vertical motion in terms of components associated with system movement, maintaining a constant thermal structure, and with the development of that structure. The former links with the isentropic relative-ow analysis technique. Viewed in a moving frame of reference, the measured development of a system depends on the velocity of that frame of reference. The requirement that the development should be a minimum provides a quantitative method for determining the optimum system velocity. The component of vertical velocity associated with development is shown to satisfy an omega equation with forcing determined from the relative advection of interior PV and boundary temperature. The analysis carries through in the presence of diabatic heating provided the omega equation forcing is based on the interior PV and boundary thermal tendencies, including the heating effect. The analysis is shown to be possible also at the level of the semi-geostrophic approximation.The analysis technique is applied to a number of idealized problems that can be considered to be building blocks for midlatitude synoptic-scale dynamics. They focus on the in uences of interior PV, boundary temperature, an interior boundary, baroclinic instability associated with two boundaries, and also diabatic heating. In each case, insights yielded by the new perspective are sought into the dynamical behaviour, especially that related to vertical motion.

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The Diagnosis of Synoptic-Scale Vertical Motion in an Operational Environment

Cited by 47 publications

References 0 publications

The Climatology of Synoptic-Scale Ascent over Western North America: A Perspective on Storm Tracks

The Climatology of Synoptic-Scale Ascent over Western North America: A Perspective on Storm Tracks

Observational Analysis of Heavy Rainfall Mechanisms Associated with Severe Tropical Storm Bilis (2006) after Its Landfall

The omega equation and potential vorticity

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