Estimates of path attenuation for the TRMM radar

It is well known that radar signals above 10 GHz can suffer significant attenuation in rain even over the relatively short rain paths associated with near-nadir viewing angles. Also well known is the problem of instabilities in estimating the radar reflectivity factor, Z, from measurements at a single attenuating wavelength radar. For a single-wavelength, singly polarized, non-Doppler radar such as the TRMM radar, four approaches are presently available for estimating attenuation: the Hitschfeld-Bordan, the surface reference technique (SRT), the 'slope method' and the mirror-image. A combination of the first 3 methods is used in a hybrid algorithm for rain estimation. Assessing the accuracy of the SRT is, therefore, important in determining the reliability in correcting for attenuation effects.