Hydrodynamic basis of formation of large-scale water circulation in the caspian sea: 1. asymptotic theory

Abstract

Hydrodynamic asymptotic theory of formation of large-scale circulation of Caspian Sea water is proposed. Seasonally averaged mean annual currents are studied; the problem is formulated under a linear baroclinic model of steady currents. The vertical Ekman number E V = A/ΩH 2(A is the kinematic coefficient of vertical turbulent exchange, Ω = 2ω sinφ is the Coriolis parameter, H is the mean sea depth) is a small parameter E V ≪ 1which allows the method of matched asymptotic expansions to be used. Depressions in the Middle and Southern Caspian are shown to play the principal role in the formation of the structure of large-scale water circulation. According to the proposed theory, the isobath passing through the saddle point on the Apsheron step (separatrix isobath) plays an important part in the dynamics of currents.