UHF Profiler

The basic measurement made by the UHF profiler every 30 s or so is the full Doppler spectrum of targets as a function of range. An example of such data is shown to the right. On the right side of the graph, the measurement of reflectivity with height is shown. On the main window, each of the 33 curves show the relative contribution to the reflectivity of targets moving at a given vertical velocity (downward when positive) as a function of height. Three types of echoes can be identified: clear air echoes (0-1 km height) with velocity near 0; drizzle (0-1.6 km height) will fall velocities centered around 2.5 m/s; stratiform precipitation (0.5-3.5 km) in the form of snow at 3.5 km and rain below 3 km. At that time, the rain was just starting (see the image below around 13:26 near the center) and was still mainly above 1.8 km, masking the drizzle echoes. Only a few drops had already reached lower altitudes, with the largest (and fastest) ones being the closest to the surface.

From this "source" information, various plots of more practical use can be made. For example, this time-height plot of reflectivity (in colors) and wind velocity (using the wind barb convention) was computed using the reflectivity information measured on the vertical beam and the Doppler information from the beams at 5 different pointing angles (one up, and the other tilted to the north, east, south, and west). Echoes from precipitation (blue to orange), birds (the 3 bullseyes echoes below 1 km). and clear air targets (the low level and the labeled echoes in purple) can be observed at the same time as the winds measured by the profiler during that event.