  Hadley cells dominate the meridional circulation of terrestrial atmospheres.
The Solar System terrestrial atmospheres, Venus, Earth, Mars and Titan, exhibit
a large variety in the strength, width and seasonality of their Hadley
circulation. Despite the Hadley cell being thermally driven, in all planets,
the ascending branch does not coincide with the warmest latitude, even in cases
with very long seasonality (e.g., Titan) or very small thermal inertia (e.g.,
Mars). In order to understand the characteristics of the Hadley circulation in
case of extreme planetary characteristics, we show both theoretically, using
axisymmetric theory, and numerically, using a set of idealized GCM simulations,
that the thermal Rossby number dictates the character of the circulation. Given
the possible variation of thermal Rossby number parameters, the rotation rate
is found to be the most critical factor controlling the circulation
characteristics. The results also explain the location of the ascending branch
on Mars and Titan.
