  Near-surface flows measured by the ring-diagram technique of local
helioseismology show structures that persist over multiple rotations. We
examine these phenomena using data from the {\em Global Oscillation Network
Group} (GONG) and the {\em Helioseismic and Magnetic Imager} (HMI) and show
that a correlation analysis of the structures can be used to estimate the
rotation rate as a function of latitude, giving a result consistent with the
near-surface rate from global helioseismology and slightly slower than that
obtained from a similar analysis of the surface magnetic field strength. At
latitudes of 60$^{\circ}$ and above the HMI flow data reveal a strong signature
of a two-sided zonal flow structure. This signature may be related to recent
reports of "giant cells" in solar convection.
