Atmospheric circulations of terrestrial planets orbiting low mass stars

In the near future, Earth-size planets will be discovered orbiting stars other than the Sun. The stars orbited by these planets are most likely to have lower masses than our Sun, which will cause these planets to be tidally locked to their parent star. Using the GENESIS GCM, a variety of Earth-like planets with different orbital periods that were tidally locked to their parent stars were studied. These planets had surfaces that were either totally solid or totally liquid. In studying the results of the modeling, it was found that these planets have very different atmospheric circulation characteristics dependent on surface type and rotation rate. For the dry planets, the mean surface temperature increased with decreasing rotation rate in general. However, an abrupt transition between two different circulation regimes was discovered near a 4 day rotation period. Planets that rotate faster had a more Earth-like circulation while those that rotate slower were dominated by stationary Rossby waves. The transition between the two regimes was found to be metastable. For the ocean covered planets, the circulation regimes were seen; however the mean surface temperature increased with increasing rotation rate, which is the opposite trend seen in the dry planets. These findings have implications for the habitability of these soon-to-be-discovered planets.