Determining the vertical profile of reflectivity using radar observations at long range

The Vertical Profile of Reflectivity (VPR) plays an important role when estimating the rain rate at the surface and has been the subject of radar meteorology research for many years. The VPR can either be sampled directly from observations that are close to the radar where the impact of the convolution with the beam pattern can be ignored, or the parameters for a theoretical form for the VPR are estimated using the available observations or climatology. In either case, a significant difficulty arises when a rain band approaches the radar and quantitative precipitation estimates are required before any detailed observations of the VPR at close range are possible. Long range in this context is the range where the height of the lowest elevation angle in the volume scan is greater than the wet bulb freezing level at that time, and therefore only limited information on the shape of the bright band is available. This paper uses a modified version of the VPR model proposed by Fabry (1997) and evaluates strategies to make optimum use of empirical observations, and how estimates for the model parameters could be updated in time. The technique is demonstrated using case studies of widespread rainfall over Sydney and Brisbane, Australia. Comparing the final technique to both the current short range and long range methods indicates that the parameterised VPR is able to provide similar VPR accuracies as the short range, with great improvement on the current long range method, making it suitable for rainfall corrections.