There's been a recent upsurge of interest in evidence for rocky planets orbiting red dwarf stars. Red dwarfs are very common in the the Milky Way and can live much longer than larger stars such as our Sun. The possible existence of several rocky planets in the habitable zone of Gliese 581 has sparked a number of investigations and simulations. My interest is not so much whether this particular system pans out, but in possibility that an earth like planet will eventually be confirmed. en.wikipedia.org/wiki/Gliese_581_g From an SF point of view, Glies 581g is interesting because it could be earthlike while at the same time, being very different. First, it will almost certainly be tidally locked meaning one side faces its star at all times. At first this seems like strong negative, but it's argued that a deep liquid water oceanic planet with an atmosphere at least as dense as earth could distribute enough heat from the bright side to the dark side to keep the the water from freezing. I've been thinking about the possible atmospheric circulation on such a planet. Assuming it is tidally locked (and there is no axial tilt) any point on the surface of the bright side would receive a more or a less constant level of light according to its position. It would maximal at the subsolar point and minimal at the perimeter of the bright side. There would be no day-night or seasonal cycles. The subsolar point would be an idealized "thermal warm pole" and its antipode on the dark side would be the "cold pole". Constructing a polar coordinate system on this basis might be more useful than the typical system based on the poles of rotation. I would expect cold surface air at the cold pole to circulate in a spiral manner toward the warm pole, and a return circulation at altitude. In the absence of significant Coriolis forces, I would not expect the of kinds wind belts we see on Earth (trade winds and equatorial easterlies, westerlies, polar easterlies) or the many more seen on Jupiter. The spiral pattern would be caused by the same forces that create a spiral pattern in water draining in a sink. Water cannot flow into the drain flowing in a straight line. Whether the flow is clockwise or counterclockwise would depend on initial conditions and not Coriolis forces. Does this seem to be correct?