In analogy to the auroral substorm concept, workers have recently attempted to describe the radar aurora as a sequence of radar auroral substorms. All of the radar substorm signatures to date have been characteristic features that appear on range-time-intensity plots of fixed beam radar data. However, because fixed beam radars are capable of probing along only one dimension (range), it is often difficult to interpret those radar signatures in terms of physical processes. In this paper we present three two-dimensional radar substorm signatures obtained with a phased array radar operated at Homer, Alaska. We show that all three of the radar signatures are closely associated with the expansive and/or recovery phases of auroral substorms. Two other radar substorm signatures, which can be detected only by a rapid scan phased array radar, are presented in a companion paper (Tsunoda and Fremouw, 1976)