energies are in code units, and are plotted as changes relative to their initial values. The energies of the cloud and background are calculated as sums across the entire computational grid, with the contribution from each zone weighted by the fractional amount of the appropriate tracer present in each zone. This should minimize any confusion due to mixing of the cloud and background gas. The high order of the advection scheme also minimizes numerical diffusion (Anninos, Fragile, & Murray 2003).

As can be seen in Figure \[fig:mod1en\], the total energy of the cloud decreases as it falls in the gravitational potential. The increase in $E_{Tot}$ at late times is due to the upward motion of cloud material entrained within the vortices that form behind the cloud. The kinetic energy of the cloud increases until it reaches a terminal infall speed at $t\approx10$, According to Equation (\[eq:vterm\]), the terminal speed of infalling clouds is an increasing function of their size. As a cloud breaks up into many smaller pieces, its kinetic energy decreases along with $V_t$. The internal energy of the cloud does not change significantly during its descent and breakup. The distance travelled before breakup is $\sim 30
S(y_0)$. The 