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Abdul Jabbar Abdullah

Abstract

In this paper-an attempt is made to study the mechanical influence of a surge of cold air on cyclogenesis. It is assumed that a quasistationary front exists and that cold air starts pushing at the rear of the underlying cool air. It is shown that the cool air acquires an energy which is of the same order of magnitude as the hydro-dynamical energy of the appropriate frontal wave. The suggestion is made that the events which occur in this process are analogous to those which take place in the hydraulic phenomenon known as the “bore,” and therefore a similar method of analysis is used.

An actual example of cyclogenesis associated with a surge of cold air is described, and two other examples are studied for the sake of quantitative comparison with the results computed from one of the equations derived in this work. The ideas upon which the theoretical work has been based seem to agree qualitatively with observation. Quantitative agreement exists as far as orders of magnitude are concerned.

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Abdul Jabbar Abdullah

Abstract

An attempt is made to show that a single elevation of permanent type may exist in a two-layer atmosphere at the interface between the two layers. The compressibility of the air, friction, the earth's rotation, and its spherical shape are neglected. It is assumed that the free surface of the upper layer remains undisturbed at all times, and that the hydrostatic relation holds in the upper layer when the lower layer is disturbed.

It is found that, under these simplifying assumptions, internal solitary waves may exist in the atmosphere. The shape of these waves and the conditions attending their formation are found to be identical with those of shallow water waves as given by Keller.

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Abdul Jabbar Abdullah

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Abdul Jabbar Abdullah

Abstract

In this paper an attempt is made to explain the shape and behavior of the spiral bands of a hurricane. The main hypothesis is that the bands are associated with gravitational waves of finite amplitude propagating at. the interface of a high-level inversion. An external source of disturbance is postulated in the form of a fresh surge of air at the exterior region of the hurricane. It is shown that this mechanism leads to the formation of bands of the required shape. The spiral bands are therefore related to the squall lines of temperate latitudes. Two numerical examples are worked out to illustrate the proposed mechanism.

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Abdul Jabbar Abdullah

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No abstract available.

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ABDUL JABBAR ABDULLAH

Abstract

In this paper an attempt is made to construct a dynamical model for a tornado that may explain some of its known features. The assumption is made that a tornado is dynamically equivalent to a combination of a pure sink and a pure vortex in the hydrodynamic sense. The compressibility of the air is taken into account, but the air is assumed to be dry. Friction is neglected and the motion induced by the disturbance is assumed to be horizontal.

It is found that, because of the compressibility of the air, the flow is separated into three main regions, an outer region in which the flow is subsonic, an innermost region which cannot belong to the outer flow, and a middle region that separates the two, in which the flow is supersonic. Formulas are derived by which the radii of these regions may be computed. The minimum possible pressure and the maximum possible speed are computed. The vertical shape of the funnel is also computed on the assumption that it is parallel to the surface of the critical flow.

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Abdul Jabbar Abdullah

Solitary waves have been observed in shallow water. In the present paper some evidence is presented for the existence of similar phenomena in the atmosphere. A possible mechanism for the formation of atmospheric solitary waves is described, and a case study is discussed in support of this mechanism. Some speculations are made about some possible effects of these disturbances on the local weather.

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Abdul Jabbar Abdullah

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No abstract available.

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ABDUL JABBAR ABDULLAH

Abstract

In this paper an attempt is made to explain the phenomenon of cloud stratification which is occasionally observed in the atmosphere. The leading thought is that these stratifications are caused by internal gravity waves. The atmosphere is assumed to consist of two layers of compressible air. The lower layer has a constant lapse rate, and the upper layer is isothermal. The quasi-static assumption is made. This assumption is found to be justifiable in the range of waves under consideration. It is found that waves whose phase velocities are of the order of 10m. sec.−1 are capable of producing three strata whose elevations fall within the limits of observed altitudes of tropospheric clouds. The proposed mechanism is also found to be consistent with the observed heights of some stratospheric clouds.

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ABDUL JABBAR ABDULLAH

Abstract

This paper attempts to explain the “whining” or “hissing” sound reported from tornadoes. The leading hypothesis is that the air masses involved in the tornado circulation execute some free vibrations. It is found that these vibrations may be in the audible range for a small vortex whose radius is of the order of 10 m. or less. A formula is obtained which relates the frequency of the tone to the inner radius of the vortex. This formula is amenable to experimental verification.

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