Use of mesoscale models in bright band correction algorithms

If accurate estimates of rainfall at the ground are to be made using radar it is important to correct for the vertical profile of reflectivity and especially the enhancement associated with the bright band. One approach, used in Europe, is to assume that the height of the bright band is given by the height of the freezing level held in operational forecasting models. An alternative approach has been recently proposed, whereby the height of the bright band is derived from an analysis of the radar returns at various elevations, and then this height information is used to improve the temperatures in the mesoscale model. We have explored which of these approaches is most efficient. The height of the bright band has been inferred to an accuracy of 60m from a two year time series of vertically pointing 94GHz cloud radar and found to be in good agreement with the height of the zero degree wet bulb temperature in both the Met Office and ECMWF operational models. Our initial conclusion is that the accuracy of the freezing levels in the operational models is better than would be derived from operational scanning radars.