Physical Oceanography (Dec 2022)
Critical Levels of the Sea Breeze Сirculation within the Framework of Linear Theory
Abstract
Purpose. The present paper is aimed at solving (within the framework of linear theory) a problem on the influence of critical levels on an inertia-gravity wave with the scale typical of the sea breeze circulation in the presence of an average background synoptic flow (perpendicular to the coast) with a vertical shear. Methods and Results. To solve the problem, the generalized Taylor – Goldstein equation was used with the regard for rotation. The coefficients’ behavior, having been analyzed, showed that at the equator, for a gravity internal wave (generated by a heat source on the surface) with the daily frequency, there existed a single critical level, at which the wave was absorbed. In the tropics, an inertia-gravity wave of the daily period passes through two critical levels and the attenuation region located between them. At the mid-latitudes, the generated wave, starting from the surface, is in the attenuation zone, then passes the critical level and propagates above it. To analyze the solution behavior, the Cauchy problem on the wave passage through the critical level was solved. The solution near the critical level was obtained numerically. Conclusions. For the selected values of stratification and background wind speed, the absorption coefficients of the vertical momentum flux were calculated for the equator and those of the vertical angular momentum flux – for the tropics and middle latitudes. The absorption coefficient value at the equator is in complete agreement with the results obtained in the earlier published papers. Comparing the values of the absorption coefficients of the vertical momentum flux/vertical angular momentum flux at different latitudes, one can note that the strongest attenuation takes place at 15°, and the weakest one – at 45°.
