Model configuration and boundary condition

Simulations are done in a three-dimensional (3-D) framework. The 3-D simulation has a domain of 45$\times$45$\times$55 grid points with a 50 m grid spacing in the horizontal and 25 m grid spacing in the vertical from the surface to the domain top (1375 m). The time step is 2s.

The lateral boundary conditions are cyclic. The boundary condition at the model top corresponds to a rigid lid, with a Rayleigh friction absorbing layer applied to the momentum equations and to the thermodynamic equation. The surface parameterization based on that of Louis [1979] is used, and the bottom boundary is specified to be consistent with surface conditions observed during FIRE/SHEBA, with a specified surface temperature of 266 K. The large-scale subsidence is prescribed by w_sub=-D*z. Where $D=5.\times10^{-6} s^{-1}$ is the large-scale divergence, and z is the model height in m. This gives an averaged subsidence velocity at the inversion of -0.25 cm s^-1.