An Automated Bright-band Height Detection Algorithm for Use with Vertically Pointing Doppler Radars

Because knowledge of the snow level is critical to weather forecasters, river forecasters, and other users, the Weather and Climate Applications Division of the NOAA Environmental Technology Laboratory has developed an objective algorithm to detect the bright-band height from profiles of radar reflectivity and Doppler vertical velocity collected with a commercially available Doppler wind profiling radar. The algorithm uses vertical profiles to detect the bottom portion of the bright band, where vertical gradients of radar reflectivity and Doppler vertical velocity are negatively correlated. A search is then performed to find the peak radar reflectivity above this feature, and the bright-band height is assigned to the altitude of the peak. Reflectivity profiles from the off-vertical beams produced when the radar is in a Doppler beam swinging mode provide additional bright-band measurements. A consensus test is applied to sub-hourly values to produce a quality-controlled, hourly-averaged bright-band height. The bright-band height is a better estimate of the snow level than the melting level because of the time required for ice particles to melt as they descend. This paper discusses the development of the algorithm, testing and evaluation that were performed on the algorithm, and some specific applications of the algorithm to weather and hydrometeorological forecasting.