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Julia Paegle and Jan Paegle

Abstract

The effect of friction in strongly divergent steady flows is studied. It is found that friction weakens flow divergence out of strong high-pressure centers, contrary to the more commonly studied case for weaker high-pressure centers in rotating flows, for which friction produces divergence. The stability of the solution is discussed for the general case on a linear basis. Nonlinear analytic solutions are presented for the case of no deformation in the flow. The conclusions are quantified in a drag, deformation and Laplacian of geopotential parameter space.

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Julia Nogues Paegle and Jan Paegle

Abstract

Observed perturbation kinetic and available energy are presented for a region about 3000 km on a side to study the horizontal homogeneity and general characteristics of geostrophic motions. Frequency spectral analysis is used to determine the dependence of these characteristics on time scales. For all time scales considered the perturbation energies display horizontal inhomogeneities, but these are less pronounced for shorter time scales. For time scales smaller than 4 days the spectra of horizontal kinetic and available potential energies decrease with increasing frequency, and approximately fit power laws with exponents between −2 to −3.5, depending on location. The frequency spectra for geostrophic vertical velocities are markedly different for different climatic locations. The frequency spectra are related to one-dimensional wavenumber spectra by introducing suitable transformation of variables. The results obtained for the higher end of these spectra are interpreted in terms of those predicted by Charney for quasi-geostrophic turbulence.

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Julia Nogues Paegle and Jan Paegle

Abstract

Time-dependent flow solutions for steady supergradient pressure patterns are presented for a variety of initial flow configurations. These solutions discriminate initial conditions and pressure patterns that produce stable and unstable flow evolutions. It is shown that steady-state divergent flows are realizable for commonly observed pressure patterns of the upper troposphere. In these cases, the steady state is approached on relatively short time scales. Solutions agree roughly with observed features of atmospheric flows and constitute a plausible explanation for strong upper level outflows.

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Julia Nogues Paegle and Jan Paegle

Abstract

Frequency spectra of heights and geostrophic vorticities are computed for several points over the western continental United States and eastern Pacific. These spectra exhibit horizontal variations which appear to be, at least partly, attributable to the underlying topography. This conclusion is supported by a highly simplified, barotropic, mountain-flow model.

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Jan Paegle and Julia N. Paegle

Abstract

One year of geopotential data obtained from the National Meteorological Center and the National Center for Atmospheric Research are diagnosed for the occurrence of non-elliptic regions with respect to the balance equation. The highest frequencies of such occurrences appear at 200 mb over the subtropical oceans where there are few radiosonde observations. Substantial 200 mb frequencies are also found over the United States in the summer season above a reliable data net. A diagnosis of flow divergence implied for the non-elliptic data by a theoretical analysis of Paegle and Paegle (1974) produces values greatly in excess of. typical observations. This suggests that the gridding of the data by objective analysis may not have been adequate and/or that the aforementioned theory overestimates flow divergence in these regions. It is likely that non-elliptic data are important for initialization of primitive equation forecast models. It may be inferred that greater data accuracy, as well as better initialization techniques within non-elliptic regions, are required.

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Jan Paegle and Julia N. Paegle

Abstract

An efficient alternative to the customary balance equation solution procedures is described which gives very similar solutions for those cases when the balance equation is elliptic. This alternative invokes some assumptions that are not usually applied to the nonlinear balance equation, but which are justified by comparisons with the standard solutions to the balance equation in both rectangular and spherical geometries. The solution tends toward a flow with zero absolute vorticity as the pressure field tends toward configurations for which the balance equation is non-elliptic. Such non-elliptic pressure fields correspond to force fields with sufficient positive divergence with respect to space to generate flow divergence. In this case a non-divergent balanced solution may not exist, and is physically meaningless if it does exist, but a reasonable divergent balanced solution can be obtained by the proposed technique.

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Julia Nogués-Paegle

An informative and stimulating conference on phenomenological studies, data systems, analysis and assimilation techniques, and numerical prediction motivated by the Global Weather Experiment (GWE) took place during the AMS annual meeting in January 1986. This conference is summarized and includes thoughtful contributions provided by R. Fleming, program chairman; J. Brown, Jr.; J. Fein; R. Greenfield; D. Johnson; E. Kalnay; D. Sargeant; and J. Theon.

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Julia N. Paegle

Abstract

Regression techniques are applied on stratified and non-stratified data to obtain prediction equations for the probability of precipitation over the western continental United States. The stratification is based on 500-mb winter types. The equations are tested on an independent data sample and it is found that the stratification leads to considerable improvement of the forecasts.

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Julia Paegle and Eugene Robl

Abstract

A three-component barotropic flow is considered to study the time behavior of the joint probability density function of spectral amplitudes. The beta effect is included by allowing the phase of the waves to be a linear time function. Analytic and numerical integrations are obtained for cases with and without beta. It is found that the addition of the beta effect produces important changes in the behavior of the probability function, particularly for long times. Initial correlations between the wave components are allowed and found to have some impact on the second moments of the distribution for the first two days. After this time, the nonlinearities build correlations such that the fields are independent of the initial correlation values.

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Julia N. Paegle

Abstract

A system of three Fourier components in a barotropic channel flow is considered to investigate the influence of topography on a neutral Rossby wave. Analytic solutions show how topography induces a nonlinear oscillation of the mean flow-wave system.

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