  We study the equations of motion for a barotropic fluid in spherical
symmetric flow. Making use of the Riemann invariants we consider the
characteristic form of these equations. In a first part, we show that the
resulting constraint equations along characteristics can be solved globally
away from the center of symmetry. In a second part, given data on two
intersecting characteristics, we show existence and uniqueness of a smooth
solution in a neighborhood in the future of these characteristics.
