  Orbital phase-dependent variations in thermal emission and reflected stellar
energy spectra can provide meaningful constraints on the climate states of
terrestrial extrasolar planets orbiting M dwarf stars. Spatial distributions of
water vapor, clouds, and surface ice are controlled by climate. In turn, water,
in each of its thermodynamic phases, imposes significant modulations to thermal
and reflected planetary spectra. Here we explore these characteristic spectral
signals, based on 3D climate simulations of Earth-sized aquaplanets orbiting M
dwarf stars near the habitable zone. By using 3D models, we can
self-consistently predict surface temperatures and the location of water vapor,
clouds, and surface ice in the climate system. Habitable zone planets in M
dwarf systems are expected to be in synchronous rotation with their host star
and thus present distinct differences in emitted and reflected energy fluxes
depending on the observed hemisphere. Here we illustrate that icy, temperate,
and incipient runaway greenhouse climate states exhibit phase-dependent
spectral signals that enable their characterization.
