Comments on "Millimeter wave propagation in arid land-a field study in Riyadh

The commenter notes that the paper by A.A. Ali and M.A. Alhaider (see ibid., vol.40, no.5, p.492-9, May 1992), the 0.88 mu m attenuation by rain with rates exceeding 7 mm/h was observed to be about 30% lower than expected from computation. This is of the same order of discrepancy as was observed by T.S. Chu and D.C. Hogg (1968) in measurements at 0.63, 3.5, and 10.6 mu m during heavy rains in New Jersey. This reduction, about 30%, as Chu and Hogg confirmed by calculation is due to forward scattering by the raindrops, many of which are considerably larger than the wavelength, as Ali and Alhaider point out. A reference to the paper by TaShing Chu and the commenter is corrected.< >