Nowcasting Surface Snowfall Rates by Utilizing Radar Reflectivity and Velocity–Azimuth Display Vertical Wind Profiles

Snow events can have significant impacts on human activities such as agriculture, business, transportation, and recreation. Aircraft de-icing and anti-icing procedures and the clearing of snow from airport runways and public roadways is paramount to safety when snow accumulation is occurring. In order to accurately predict and respond to snowfall accumulation events, a better understanding of mesoscale spatial distribution of snowfall rate is required. A common tool for the determination of snowfall rate and areal distribution is radar, but due to slow snowfall velocities (~1-2m/s) and the impact of wind speed on horizontal snow particle velocity, determination of snowfall rate at ground level can be difficult when utilizing radar scans at higher elevations. Most weather radar systems such as the National Weather Service's Weather Surveillance Radar, 1988, Doppler (WSR-88D) radar systems as well as X-band research radars are equipped a velocity-azimuth display (VAD) algorithm that creates vertical wind velocity profiles of velocity and direction at a point. This project's objective is to provide a proof of concept for a snowfall nowcasting system that utilizes the VAD profiles in conjunction with radar measured snowfall rates to give a more accurate determination of ground level snowfall rates that can then be verified by ground-based all weather precipitation gauges.