Title: Demarcating circulation regimes of synchronously rotating terrestrial planets within the habitable zone,
Abstract: We investigate the atmospheric dynamics of terrestrial planets in synchronous
rotation within the habitable zone of low-mass stars using the Community
Atmosphere Model (CAM). The surface temperature contrast between day and night
hemispheres decreases with an increase in incident stellar flux, which is
opposite the trend seen on gas giants. We define three dynamical regimes in
terms of the equatorial Rossby deformation radius and the Rhines length. The
slow rotation regime has a mean zonal circulation that spans from day to night
side, with both the Rossby deformation radius and the Rhines length exceeding
planetary radius, which occurs for planets around stars with effective
temperatures of 3300 K to 4500 K (rotation period > 20 days). Rapid rotators
have a mean zonal circulation that partially spans a hemisphere and with banded
cloud formation beneath the substellar point, with the Rossby deformation
radius is less than planetary radius, which occurs for planets orbiting stars
with effective temperatures of less than 3000 K (rotation period < 5 days). In
between is the Rhines rotation regime, which retains a thermally-direct
circulation from day to night side but also features midlatitude
turbulence-driven zonal jets. Rhines rotators occur for planets around stars in
the range of 3000 K to 3300 K (rotation period ~ 5 to 20 days), where the
Rhines length is greater than planetary radius but the Rossby deformation
radius is less than planetary radius. The dynamical state can be
observationally inferred from comparing the morphology of the thermal emission
phase curves of synchronously rotating planets.