Correct a sign of pseudo thickness in Overview.

Author: hyungyukang

components/omega/doc/design/OmegaV1GoverningEqns.md

@@ -16,7 +16,7 @@ Add later, if it seems necessary. There is a toc on the left bar.
 
 This design document describes the governing equations for Omega, the Ocean Model for E3SM Global Applications. Overall, Omega is an unstructured-mesh ocean model based on TRiSK numerical methods ([Thuburn et al. 2009](https://www.sciencedirect.com/science/article/pii/S0021999109004434)) that is specifically designed for modern exascale computing architectures. The algorithms in Omega will be mostly identical to those in MPAS-Ocean, but it will be written in c++ rather than Fortran in order to take advantage of the Kokkos performance portability library to run on GPUs ([Trott et al. 2022](https://ieeexplore.ieee.org/document/9485033)). Significant differences between MPAS-Ocean and Omega are:
 
-1. Omega is non-Boussinesq. This means that the full 3D density is used everywhere, and results in a mass-conserving model. MPAS-Ocean and POP were Boussinesq, so that a reference density $\rho_0$ is used in the pressure gradient term, and were therefore volume-conserving models. In Omega the layered mass-conservation equation is in terms of pseudo-thickness ($\tilde{h}=\Delta p / \rho_0 g$). In MPAS-Ocean the simple thickness ($h=\Delta z$) is the prognostic volume variable (normalized by horizontal cell area).
+1. Omega is non-Boussinesq. This means that the full 3D density is used everywhere, and results in a mass-conserving model. MPAS-Ocean and POP were Boussinesq, so that a reference density $\rho_0$ is used in the pressure gradient term, and were therefore volume-conserving models. In Omega the layered mass-conservation equation is in terms of pseudo-thickness ($\tilde{h}=-\Delta p / \rho_0 g$). In MPAS-Ocean the simple thickness ($h=\Delta z$) is the prognostic volume variable (normalized by horizontal cell area).
 1. Omega will use the updated equation of state TEOS10, while MPAS-Ocean used the Jackett-McDougall equation of state.
 
 The planned versions of Omega are: