The Divergence-free Net Coriolis Force creates Vertical Geostrophic
Balance and Westward tilted Atmospheric Convection
Abstract
There has been increasing realization that the non-traditional Coriolis
force terms may have a significant effect on convective circulation and
organization in the tropics. In this talk, we introduce the concept of
the net Coriolis force of a fluid dynamical flow. In order to compute
the net Coriolis force, we assume incompressible flow - and therefore
incompressible net Corolis force. Through the Leray projection we are
able to construct, both, the pressure needed to maintain an
incompressible force, and the net Coriolis force, itself. We explore the
effects of the net Coriolis force on basic flows by decomposing the
velocity field using the Helmholtz decomposition, and we describe
poloidal and horizontal flows separately. We then compute the net
Coriolis force associated with the Traditional Corolis terms
(proportional to the sine of latitude) and, separately, the net
Non-Traditional Coriolis terms (proportional to the cosine of latitude).
We show that all poloidal circulations - which are flows which lack a
vertical component of vorticity - are in vertical gesotrophic balance.
Therefore, the pressure induced by such flows is simply computed without
the need to invert a Laplacian. Using the Dynamics of Non-rotating
Updraft Tori (DoNUT), which is a polodial circulation framework
introduced by Igel & Biello (2020) to describe the full kinematic
circulation of atmospheric convection, we show that the net
non-traditional Coriolis force has zero component in the vertical
direction, is westward in the regions of upward flow, and recirculates
eastward poleward of the upward flow. The resulting circulations lead to
vertical/westward oriented momentum flux from the resulting Reynold’s
stress terms. We will conclude by discussing implications of these
circulations for tropical convective organization.