Correction of Radar QPE Errors Associated with Partial Bright Band Observations Near the Ground

摘要

@@ 1. Introduction The melting of aggregated snow/crystals often results in an enhancement of the reflectivity obseNed by weather radars, and this is the so-called bright band (BB). The primary cause of the enhancement is a rapid increase in the dielectric constant of hydrometeors at the top of the melting layer followed by an increase of fall velocities of melting snowflakes toward the end of the melting process. The locally high reflectivity causes significant overestimation in radar quantitative precipitation estimates if no appropriate correction is applied. When the melting layer is very close to the ground, it often occurs that only a partial bright band can be observed by the radar. Since no information is available below the BB can be obtained from radar observations, the partial BB often leads to large overestimations in radar QPEs. To correct for these large errors, an empirical relationship of BB peak and BB bottom is developed from high-resolution precipitation profiler data. The empirical relationship is combined with the BB top and peak information from the apparent vertical profile of reflectivity (VPR) and an estimated BB bottom is derived. Radar QPEs are then corrected based on the estimated BB bottom. The methodology has been tested for two events over the plain area in the United States. The method is shown to be very effective in reducing the overestimation errors, and the corrected radar rainfall estimates compared much better with gauge observations than those without the correction.