“Horizontal” Reduction of Pressure to Sea Level: Comparison against the NMC's Shuell Method

Mesinger, Fedor; Treadon, Russell E.

doi:10.1175/1520-0493(1995)123<0059:roptsl>2.0.co;2

Cited by 16 publications

(12 citation statements)

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“…Differences in the pressure reduction method can introduce errors during interpolation of pressures from coarser to finer grids during model initialization over complex terrain. Brewer et al [14] report that the Shuell pressure reduction [31,32] used in the NARR often results in a closed low pressure over eastern Washington and pressure ridging over higher terrain during summer months, while the Mesinger pressure reduction [33] (e.g., used in the Eta Model) does not produce either of these features. The Mesigner method was developed to mitigate "unnatural-looking" small-scale terrain-following features in the pressure field [34].…”

Section: Gap Winds and Operational Modelingmentioning

confidence: 99%

Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

et al. 2018

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This work investigates gap winds in a steep, deep river canyon prone to wildland fire. The driving mechanisms and the potential for forecasting the gap winds are investigated. The onset and strength of the gap winds are found to be correlated to the formation of an along-gap pressure gradient linked to periodic development of a thermal trough in the Pacific Northwest, USA. Numerical simulations are performed using a reanalysis dataset to investigate the ability of numerical weather prediction (NWP) to simulate the observed gap wind events, including the timing and flow characteristics within the canyon. The effects of model horizontal grid spacing and terrain representation are considered. The reanalysis simulations suggest that horizontal grid spacings used in operational NWP could be sufficient for simulating the gap flow events given the regional-scale depression in which the Salmon River Canyon is situated. The strength of the events, however, is under-predicted due, at least in part, to terrain smoothing in the model. Routine NWP, however, is found to have mixed results in terms of forecasting the gap wind events, primarily due to problems in simulating the regional sea level pressure system correctly.

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Section: Gap Winds and Operational Modelingmentioning

confidence: 99%

Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

et al. 2018

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“…While most existing extrapolation schemes aim to estimate as accurately as possible the sea level pressure field, the goals of this study are best served by ensuring that the data are extrapolated so as to minimize the flow attributable to the artificial subterranean PV. In this study and the subsequent papers (Part II, Part III, and Part IV), the reanalysis data are first extrapolated using the so-called Shuell procedure (Mesinger and Treadon 1995) and then postprocessed using a scheme designed to impose balance between the subterranean mass and momentum fields (Gold 2004). The postprocessing replaces static stability profiles in and near elevated orography with the neighboring atmospheric static stability and imposes geostrophic balance on the wind field in this layer.…”

Section: Data Pv Inversion and Pv Modification A Datasetmentioning

confidence: 99%

Potential Vorticity Diagnosis of the Severe Convective Regime. Part I: Methodology

Gold

Nielsen‐Gammon

2008

Monthly Weather Review

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Observational and modeling studies have shown that shear and instability are powerful predictors of the likelihood of severe weather and tornadoes. To the extent that upper-tropospheric forecast errors can be described as potential vorticity (PV) anomalies on the forecasted PV field, knowing (and being able to quantify) the effects of such errors on shear and instability would allow forecasters to anticipate the effects of those errors on the likely mode of severe weather. To test the sensitivity of the severe convective environment to PV fluctuations, a PV inversion framework is adopted that utilizes nonlinear balance. The observed PV field is modified in a way that mimics realistic perturbations of trough intensity, location, or shape. Soundings, including moisture profiles, are reconstructed from the balanced geopotential height field assuming that air parcels conserve mixing ratio while their isentropic surfaces are displaced upward or downward by the addition of anomalous PV. Unperturbed balanced soundings agree reasonably well with full, unbalanced soundings, and differences are attributable to departures from nonlinear balance in areas of strong vorticity or acceleration. Balanced vertical wind profiles do not include the effects of friction, so the vertical shear of the balanced wind departs unacceptably from total shear within the lowest 1 km of the troposphere. The balanced wind perturbations are added to the total analyzed shear profile to estimate the effect of PV perturbations on shear and storm-relative helicity. By this process, the importance of typical or hypothesized upper-tropospheric forecast errors may be addressed in an idealized, case-study, or operational context.

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“…Any objective evaluation of the gradient would conclude that there is a permanent front located there. Mesinger & Treadon (1995) show that horizontally interpolating the temperatures whenever the pressure level is below ground is the most appropriate method for computing heights below ground. Since air temperatures are known where the isobaric surface cuts the high terrain, temperatures inside the region can be interpolated so that the analysis below ground is smooth with the edges.…”

Section: Fronts Over Higher Terrainmentioning

confidence: 99%

“…However, she also points out that because the process of estimating pressure level heights below ground is fraught with assumptions, it is difficult to assess the errors. Note also that the AWC's method is not as rigorous as the Mesinger & Treadon (1995) method, which solves a partial differential equation by iteration, Drawing fronts objectively but it is computationally far simpler. This is important when having to recompute heights on global data sets.…”

Section: Fronts Over Higher Terrainmentioning

confidence: 99%

Problems and solutions for drawing fronts objectively

McCann¹,

Whistler²

2001

Meteorological Applications

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A recent requirement charged to the Aviation Weather Center (AWC) is to produce significant weather charts for aviation users with, among other forecast products, forecast locations of significant fronts. To increase forecaster productivity, the AWC decided to evaluate the possibility that fronts should be first drawn objectively. Hewson (1998) describes the basic technique which uses a variation on the Renard & Clarke (1965) frontal locator function to find the fronts. The AWC had to overcome many problems in implementing Hewson's techniques. This paper illuminates the problems and describes the AWC solutions. As a result of the AWC's success, objective frontal analyses and forecasts are now a reality, and the productivity of forecasters increased. Copyright © 2001 Royal Meteorological Society

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“Horizontal” Reduction of Pressure to Sea Level: Comparison against the NMC's Shuell Method

Cited by 16 publications

References 0 publications

Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

Potential Vorticity Diagnosis of the Severe Convective Regime. Part I: Methodology

Problems and solutions for drawing fronts objectively

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