  The single-arm spiral roll state in the system of Boussinesq fluid confined
between non-rotating double concentric spherical boundaries with an opposing
temperature gradient previously reported by Zhang et al.(Phys. Rev. E, v66,
055203, 2002) has been numerically investigated in detail. It is presented that
the state can exist even in a relatively thicker gap rather than that used in
our previous reports as a travelling wave solution with a finite constant
angular velocity.
