Reproduction of Near Surface Shear Layer with Rotation

Abstract

We carry out high-resolution calculation of thermal convection in the spherical shell with rotation to reproduce the near surface shear layer (NSSL). It is thought that the NSSL is maintained by thermal convection for small spatial scales and short time scales, which causes a weak rotational influence. The calculation with the RSST succeeds in including such a small scale as well as large-scale convection and the NSSL is reproduced especially at high latitude. The maintenance mechanisms are the following. The Reynolds stress under the weak influence of the rotation transports the angular momentum radially inward. Regarding the dynamical balance on the meridional plane, in the high latitude positive correlation $\langle v'_rv'_\theta \rangle$ is generated by the poleward meridional flow whose amplitude increases with the radius in the NSSL and negative correlation $\langle v'_rv'_\theta \rangle$ is generated by the Coriolis force in the deep convection zone. The force caused by the Reynolds stress compensates the Coriolis force in the NSSL.