The flow field is fully developed channel flow---one of the simplest inhomogeneous turbulent flows. A fine line source is used to inject the scalar (temperature). The temperature injection does not affect the flow field, hence it is passive. The line source is in the spanwise (z) direction of the channel, and is located at transverse (i.e., wall-normal) locations: y/h = 0.067, 0.17, and 1.0 (where h is the channel half-width). Measurements of the resultant thermal plume for each source location are taken for two Reynolds numbers: 10400 and 22800 (where Re = Uch/nu: U c is the centerline velocity and nu is the kinematic viscosity). Hot-wire anemometry and cold-wire thermometry are used to acquire velocity and temperature data, respectively.