Effects of incorporating a brightband model in a downward-looking radar rainfall retrieval algorithm

A range-profiling method proposed for nadir-looking rain radar has been investigated using aircraft measurements of a typhoon event at 10 and 35 GHz. In order to take into account the effects of change in the hydrometeor phase along the radar beam, it was necessary to modify the original method. Instead of using an analytic expression for the retrieval of radar reflectivity, a numerical solution is described that enables one to include the melting layer contribution. Results show a marked improvement in the estimated rainfall rates even when a fairly simple brightband model is used, indicating the usefulness and necessity of incorporating a brightband model in a retrieval of rain rate with a downward-looking radar. The improvement occurs mainly in the retrieved Ka-band results and highlights the importance of the melting layer in retrieval algorithms, particularly for high frequencies.