A UHF wind profiler was used to measure a very interesting vertical profile of the raindrop size spectra in a convective rain which went over the profiler at Tsukuba, Japan. It can measure both the fall velocity of raindrops and the ambient air-motion including the mean velocity and the turbulence, which enables to derive an accurate drop size distribution from the Doppler spectra. The measured Doppler spectra had significant altitude variations. It further was found that a considerable high number of giant raindrops larger than 6 mm in diameter appeared at an altitude of 3.25 km. These giant raindrops, however, almost disappeared at altitudes below 2.75 km, while an increase in the number of smaller raindrops of less than 1.5 mm in diameter was observed. These variations are interpreted to be due to breakup. ¿ 2001 American Geophysical Union