Abstract
This paper presents a theoretical study of the disturbed isobaric surface shape in the geostrophic state of the atmosphere. It has been shown that, depending on the overheat sign at the equator, the isobaric surface has the shape of an oblate or prolate geoid. If the geostrophic wind velocity is nonzero at the poles, the local pressure extrema (minima for oblate geoid and maxima for prolate geoid) appear at the poles in the geostrophic state. This result correlates with the well-known polar vortex phenomenon and possibly can refine our understanding and interpretation of the phenomenon. In other words, the existence of polar minima and maxima of the pressure field can be the peculiarity of the geostrophic state of the atmosphere. It has been found that air must be colder than the surrounding atmosphere for initiation of the zonal eastward transport. For warm air mass, only easterly winds will be observed.
Highlights
As is generally known, the geostrophic state plays a significant part in atmosphere dynamics.It is important for understanding global climate system and local geophysical processes to know the characteristic properties of geostrophic wind [1,2,3,4]
The pressure disturbance at steady motion will decrease along the y-axis from the equator to the pole, and the geostrophic wind direction will be west to east, i.e., western flow will be observed in this case
∂pg /∂z > α∆Tρs g and the pressure disturbance gradients must obey the relation:. It follows that for the existence of the zonal eastward transport of warm air, the vertical pressure disturbance gradient must be positive and greater than a certain value:. If this condition is not satisfied, for the warm air mass, only east wind can be observed and the cold air mass will move in the eastward direction
Summary
The geostrophic state plays a significant part in atmosphere dynamics. In this paper, we place special emphasis on the polar vortex phenomenon This phenomenon represents a persistent, large-scale low-pressure area located near either of the Earth’s poles [10,11,12]. According to the modern understanding of the polar vortex formation mechanism, it results from the large-scale atmospheric circulation driven by the difference of the Earth surface heating at the poles and at the middle latitudes. The goal of the present work is to determine (even if qualitatively) the disturbed isobaric surface shape in the geostrophic state of the atmosphere. This will allow solving the above-mentioned problems
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