The Measurement Of Synoptic Scale Vertical Velocities By Vhf Doppler Radar-flat Terrain

A knowledge of vertical air velocities associated with synoptic scale meteorological phenomena is important to practical weather prediction as well a:; to an understanding of these systems. At present, these vertical velocities a re inferred from a grid of NWS upper air soundings of temperature and horizontal wind. It is possible to directly measure these very small (2-20 cm/s) velocities with a sensitive clear-air Doppler radar (wind profiler) located in flat terrain. The Flatland Radar was constructed to make these vertical velocity measurements. It is located near ChampaignNrbana, Illinois. The surrounding terrain is extremely flat and is far from any mountains which generaLe lee waves. The Flatland Radar has successfully measured small vertical v elocities which are shown to be related to synoptic scale weather systems. These measurements are made possible by the low and consistent variance of the vertical velocity encountered in the atmosphere above this site except during frontal passages and thunderstorms. time resolution with low statistical uncertainty. This allows the averaging of the data to provide 3-6 h