Frequency domain interferometry (FDI) is a method for more accurately measuring the position and thickness of various refractive index structures, as compared to the measurements under normal MST radar operation. For this paper a 7-hour data set has been collected and analyzed, forming a longer data set than previously used at stratospheric-tropospheric heights. A technique for fixing the height measurements within each range gate to be absolute rather than relative is presented. Two types of structure are present in the data, referred to as ''layers'' and ''blobs.'' The layers have a thickness of around 50--100 m, are often aspect sensitive, last for many hours, and exhibit fine altitude variations, some oscillatory. One layer descending over the experiment appears to be positioned at the top edge of a frontal surface zone in the overall meteorological structure. The blobs are thicker regions of around 600 m, are not aspect sensitive, and are short-lived. ¿ American Geophysical Union 1995