  Planetary rotation rate has a significant effect on atmospheric circulation,
where the strength of the Coriolis effect in part determines the efficiency of
latitudinal heat transport, altering cloud distributions, surface temperatures,
and precipitation patterns. In this study we use the ROCKE-3D dynamic-ocean
general circulation model to study the effects of slow rotations and increased
insolations on the 'fractional habitability' and silicate weathering rate of an
Earth-like world. Defining the fractional habitability f_h to be the percentage
of a planet's surface which falls in the 0 <= T <= 100 C temperature regime, we
find a moderate increase in f_h with a 10% and 20% increase in insolation and a
possible maximum in f_h at sidereal day-lengths between 8 and 32 times that of
the modern Earth. By tracking precipitation and run-off we further determine
that there is a rotational regime centered on a 4-day period in which the
silicate weathering rate is maximized and is particularly strongly peaked at
higher overall insolations. Because of weathering's integral role in the
long-term carbonate-silicate cycle, we suggest that climate stability may be
strongly affected by the anticipated rotational evolution of temperate
terrestrial-type worlds, and should be considered a major factor in their
study. In light of our results we argue that planetary rotation period is an
important factor to consider when determining the habitability of terrestrial
worlds.
