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This article continues and generalizes the study "On the Similarity of Quasi-Geostrophic Vortices against the Background of Large-Scale Barotropic Currents" [6] (Oceanology, Zhmur, 2024, in print). In continuation of [6], a similar formulation is considered, but for other types of background currents. In the quasi-geostrophic description for small Rossby numbers, the problem of the evolution of an arbitrarily shaped liquid volume with homogeneous potential vorticity of all vortex core particles in an equidistant background flow—horizontal flow with vertical shear and equidistant flow with barotropic and baroclinic components—is presented. Ultimately, the problem boils down to an integrodifferential equation for the evolution of the vortex core boundary. The study of this equation in dimensionless form makes it possible to find a set of dimensionless parameters that determine the similarity condition of the studied vortices. [ABSTRACT FROM AUTHOR]

The paper proposes a theory of similarity of quasi-geostrophic vortices against the background of large-scale flows. This information is useful when planning laboratory and numerical experiments to study mesoscale and submesoscale vortex dynamics of vortices interacting with currents. Special attention is paid to studying geometric similarity of phenomena. It is revealed that the complete set of dimensionless similarity numbers of baroclinic vortices includes four dimensionless parameters: the dimensionless intensity of the vortex, the geometric similarity of the background flow (the ratio of the relative vorticity to the deformation coefficient of the background flow), the coefficient of horizontal stretching of the vortex core, and the coefficient of vertical oblateness of the vortex core coinciding with the Burger number. To describe the similarity of barotropic vortices against the background of barotropic flows, the number of necessary dimensionless parameters is reduced by one number: the coefficient of vertical oblateness of the vortex core is eliminated from consideration. When studying axisymmetric vortices or vortex structures close to axisymmetric, another geometric parameter of the vortex is eliminated from consideration—the coefficient of horizontal stretching of the vortex core. As a result, the maximum possible set of similarity parameters includes four dimensionless numbers, and the minimum is two. [ABSTRACT FROM AUTHOR]

Based on the daily Japanese 55-yr reanalysis data, this study analyzes the maintenance mechanism for 53 boreal winter blocking highs around the Ural Mountains (UBHs) during 1958–2018 based on the atmospheric energy budget equations. After decomposing the circulation into background flow, low-frequency anomalies, and high-frequency eddies, it was found that the interaction between the background flow and low-frequency anomalies is conducive to the maintenance of the UBHs. Due to the southwestward gradient in the climatological mean air temperature over the Eurasian continent, it is easy for the air temperature anomalies as well as the wind velocity anomalies in the middle and lower troposphere induced by the UBHs to facilitate the positive conversion of baroclinic energy associated with the background flow into the UBHs. Likewise, the conversion of barotropic energy associated with the background flow is also evident in the upper troposphere, in which the climatological mean westerlies have evident southward gradient to the northwest of Lake Baikal and southwestward gradient over Barents Sea. Note that the conversion of baroclinic energy associated with the background flow is dominant throughout the lifecycle of UBHs, acting as the major contributor to the maintenance of the UBHs. Although transient eddies facilitate maintenance of the UBHs via positive conversion of barotropic energy in the middle and upper troposphere, they hinder the maintenance of UBHs via negative conversion of baroclinic energy in the lower troposphere. The diabatic heating anomalies tend to counteract the local air temperature anomalies in the middle and lower troposphere, which damps the available potential energy of UBHs and acts as a negative contributor to the UBHs. [ABSTRACT FROM AUTHOR]

Numerical simulations are used to study laminar vortex ring formation under the influence of background flow. The numerical setup includes a round-headed axisymmetric body with an opening at the posterior end from which a column of fluid is pushed out by a piston. The piston motion is explicitly included into the simulations by using a deforming mesh. A well-developed wake flow behind the body together with a finite-thickness boundary layer outside the opening is taken as the initial flow condition. As the jet is initiated, different vortex evolution behavior is observed depending on the combination of background flow velocity to mean piston velocity ( $$U/U_{p}$$ ) ratio and piston stroke to opening diameter ( $$L_{m}/D$$ ) ratio. For low background flow ( $$U/U_{p} =0.2$$ ) with a short jet ( $$L_{m}/D =6$$ ), a leading vortex ring pinches off from the generating jet, with an increased formation number. For intermediate background flow ( $$U/U_{p} =0.5$$ ) with a short jet ( $$L_{m}/D =6$$ ), a leading vortex ring also pinches off but with a reduced formation number. For intermediate background flow ( $$U/U_{p} =0.5$$ ) with a long jet ( $$L_{m}/D =15$$ ), no vortex ring pinch-off is observed. For high background flow ( $$U/U_{p} =0.75$$ ) with both a short ( $$L_{m}/D =6$$ ) and a long ( $$L_{m}/D =15$$ ) jet, the leading vortex structure is highly deformed with no single central axis of fluid rotation (when viewed in cross-section) as would be expected for a roll-up vortex ring. For $$L_{m}/D =6$$ , the vortex structure becomes isolated as the trailing jet is destroyed by the opposite-signed vorticity of the background flow. For $$L_{m}/D =15$$ , the vortex structure never pinches off from the trailing jet. The underlying mechanism is the interaction between the vorticity layer of the jet and the opposite-signed vorticity layer from the initial wake. This interaction depends on both $$U/U_{p}$$ and $$L_{m}/D$$ . A comparison is also made between the thrust generated by long, continuous jets and jet events constructed from a periodic series of short pulses having the same total mass flux. Force calculations suggest that long, continuous jets maximize thrust generation for a given amount of energy expended in creating the jet flow. The implications of the numerical results are discussed as they pertain to adult squid propulsion, which have been observed to generate long jets without a prominent leading vortex ring. [ABSTRACT FROM AUTHOR]