摘要:

Baroclinic waves in a rotating two-layer shear flow are observed by measuring fluctuations in the height of the interface using a technique which does not disturb the flow. Decomposition of the shape of the interface into azimuthal Fourier components shows that the wave spectrum is dominated by a single wave number, but other components have significant amplitudes. Nonlinear interactions between these components are isolated by comparing the results with the predictions of a linear stability theory. The observed interactions are reminiscent of those found by Hide, Mason and Plumb (1977) in a different system, thus demonstrating that they are a fundamental property of baroclinic waves.

ISSN:0309-1929    

DOI:10.1080/03091927908243767

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A two-level quasi-geostrophic general circulation model is developed to test various theories relating to surface albedo changes in the Sahara/Sahel regions of Africa. The heating function in the model is varied so as to examine the effects of both increases and decreases in surface albedo. Loss of vegetation cover is linked to increased surface albedo, and from the experiments, the delicate balance between the Sahara/Sahel is noted. Revegetating the Sahara would tend to decrease the surface albedo and the model shows that this experiment would be successful in reclaiming some of the desert.

ISSN:0309-1929    

DOI:10.1080/03091927908243768

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

An analysis is described of long, finite-amplitude internal waves in a stratified shear flow. Both regular and singular modes are considered with a nonlinear critical layer employed in the latter case. A three-layer model is used to develop the theory and closed-form expressions are obtained relating the phase speed to the Richardson number, the latter quantity being taken asO(1). The amplitude evolution equation is found to be either the Korteweg-de Vries equation or the Benjamin-Davis-Ono equation depending upon the distance of the more remote boundary from the edge of the shear layer.

ISSN:0309-1929    

DOI:10.1080/03091927908243769

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The periods of standing waves in closed canals can be influenced by nonhydrostatic effects if the shallow-water criterion is not satisfied In the analysis this can be handled by an expansion with respect to the square of the aspect ratio whereby the vertical accelerations can be taken into account. From the zeroth- and first-order sets of equations of motion and boundary conditions a linear partia1 differential equation governing nonviscous infmitesimal surface displacements is established. This equation (a reformulation of the linearised Boussinesq equations extended to allow for the effects of large changes of depth) together with boundary conditions constitutes, after separation of variables, an eigenvalue problem determining the periods of the standing waves. Interest has been directed towards cases with linear and quadratic bottom profiles where the depth displays a singularity, i.e. the surface intersects the bottom. The semianalytical procedure for determining the eigenvalues involves a Frobenius expansion of the general solution, whereby the coefficients of the series become functionally dependent on the eigenvalues. By applying the boundary conditions to the series solution the eigenvalues can be evaluated by numerical iteration. In order to show the effects of different degrees of nonhydrostaticity, computational as well as experimental results on the gravest mode of the abovementioned cases are presented. For varying aspect ratios of the system, the experimental data is in good agreement with the predictions.

ISSN:0309-1929    

DOI:10.1080/03091927908243770

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

During southern Foehn, there occurs within the planetary boundary layer a well-defined surface with a wind shear of typically 15 m/s and a temperature jump of about 15°C within a vertical distance of 100 m. These conditions are nearly ideal for studying shear waves and stability in the atmospheric boundary layer.

ISSN:0309-1929    

DOI:10.1080/03091927908243771

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A study of the mixed-layer deepening is conducted with a one-dimensional, third-order closure turbulence model. An approximate model that retains second-order terms in ratios of characteristic turbulence to mean-field scales is also developed. Development of the mixed layer is initiated by applying a constant wind stress and heat flux to an ocean of linear initial stratification. Results show that inside the mixed layer, the contribution of the triple-correlation terms to the turbulent energy equation is negligible. In the entrainment zone, the triple-correlation terms are of the same order of magnitude as the other significant terms. The net effect of the triple-correlation terms is to deepen the mixed layer. Various length scale prescriptions have been considered and compared against each other. The entrainment rates are calculated for a chosen range of parameter space and compared against the experimental results of Kato and Phillips (1969).

ISSN:0309-1929    

DOI:10.1080/03091927908243772

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The additional water mass of a storm surge influences tilt measurements inland from the sea in the same way as marine tides influence earth tidal measurements: they cause a deflection of the local vertical as well as a tilt of the crustal surface.

ISSN:0309-1929    

DOI:10.1080/03091927908243773

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Molodenskii's theory on the resonance effect of the liquid core predicts anomalous amplitudes in the diurnal spectrum for earth tide registrations of gravity and tilt. A two years recording of an Askania gravimeter at Kiel University has been analysed using three different numerical methods: harmonic analysis (least squares method), gliding harmonic analysis, and Fourier spectral analysis. Because of difficulties in resolving tidal waves near the resonance frequency, efforts were made towards improving the Fourier spectral analysis by successive subtraction of high amplitudes in the Fourier spectrum. The resonance of the liquid core has been observed with a high degree of confidence thereby supporting Molodenskii's model calculations.

ISSN:0309-1929    

DOI:10.1080/03091927908243774

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The propagation of planetary waves with lowest zonal modes at the 500 mb level is investigated using several methods of wavenumber—frequency analysis. Wave spectra of travelling and standing waves are presented and their appearance around the rotation frequency of the sun f0= 1/27.5 d−1is discussed. It is ascertained that, although strong travelling waves near this frequency exist over a broad latitudinal band, thcy cannot be correlated to the solar rotation.

ISSN:0309-1929    

DOI:10.1080/03091927908243775

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

In geophysical time series, such as daily temperatures, trends may be present due to global or to anthropogenic climatic changes. In this paper the quantitative estimation of the trend and of its statistical uncertainty is obtained by means of a fitting procedure, provided the stochastic behaviour of the time series has been previously determined, and the time random part of the time series is stationary. Moreover a detailed discussion on the reliability of the results is presented. The method has been tested with positive results on the minimum daily temperatures measured in bodena, Italy, since 1869.

ISSN:0309-1929    

DOI:10.1080/03091927908243776

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor