  We present theories for the latitudinal extents of both Hadley cells
throughout the annual cycle by combining our recent scaling for the ascending
edge latitude (Hill et al. 2021) with the uniform Rossby number (Ro),
baroclinic instability-based theory for the poleward, descending edge latitudes
of Kang and Lu 2012. The resulting analytic expressions for all three Hadley
cell edges are predictive except for diagnosed values of Ro and two
proportionality constants. The theory captures the climatological annual cycle
of the ascending and descending edges in an Earth-like simulation in an
idealized aquaplanet general circulation model (GCM), provided the descending
edge prediction is lagged by one month. In simulations in this and two other
idealized GCMs with varied planetary rotation rate ($\Omega$), the winter,
descending edge of the solsticial, cross-equatorial Hadley cell scales
approximately as $\Omega^{-1/2}$ and the summer, ascending edge as
$\Omega^{-2/3}$, both in accordance with our theory.
